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ABSTRACT

The status of our knowledge about the silviculture of subalpine
forests in Wyoming, Colorado, and New Mexico is described. The
ecology and resource of the Rocky Mountain subalpine are briefly
described, followed by in-depth reviews of the spruce-fir type and
lodgepole pine type. The relevant literature is included, along with
unpublished research, observations, and experience. Research
needs are considered as well as what is already known.

Oxford: 181$174:187. Keywords: Timber management, silvicul-
ture systems, subalpine ecology, Picea engelmannii, Abies
lasiocarpa, Pinus contorta.

The use of trade and company names is for the
benefit of the reader; such use does not constitute an
official endorsement or approval of any service or prod-
uct by the U. S. Department of Agriculture to the
exclusion of others that may be suitable.

USBA Forest Service May 1974

Ijtesiarch^aper RM-121^

SILVICULTURE OF SUBALPINE FORESTS
IN THE CENTRAL AND SOUTHERN ROCKY MOUNTAINS:
The Status of Our Knowledge.

Robert R. Alexander, Principal Silviculturist
Rocky Mountain Forest and Range Experiment Station1

^Central headquarters is maintained in cooperation with Colorado State Uni-
versity at Fort Collins.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

CONTENTS

Page

THE ROCKY MOUNTAIN SUBALPINE 1

ECOLOGY 1

Habitat Conditions 1

Climate 1

Geology and Relief 3

Soils and Landforms 3

Vegetation 4

Life Zones 4

Successional Status 5

Habitat Types 6

THE RESOURCE 7

Area and Volume 7

Properties and Uses of Wood 8

THE SPRUCE-FIR TYPE 10

STAND CONDITIONS 10

PAST CUTTING HISTORY 10

DAMAGING AGENTS 12

Windfall 12

Insects 13

Diseases 14

NATURAL REGENERATION REQUIREMENTS 15

Seed Supply 15

Flowering and Fruiting 15

Cone-Bearing Age 15

Time of Seedfall 15

Cone-Crop Predictability 15

Production and Periodicity 16

Seed Quality 16

Dispersal 16

Source 18

Viability 18

Seed Losses 18

Factors Affecting Germination 19

Factors Affecting Initial Survival and Seedling Establishment 20

Initial Root Growth 20

Seedbed Type 20

Climate 21

Insolation 21

Temperature 21

Moisture 22

Soil 23

Diseases 23

Animal Damage 23

Ground Vegetation 24

SITE QUALITY 25

Conventional Determination 25

Determination from Soil and Topography 25

GROWTH AND YIELD 26

Growth of Individual Trees 26

Yields Per Acre 27

Natural Stands 27

Managed Stands 27

SILVICULTURE AND MANAGEMENT OF OLD GROWTH 28

Regeneration Silviculture 28

Clearcut Areas 28

Management with Advanced Reproduction 28

Management for Reproduction After Cutting 30

Management for Artificial Regeneration 32

Partial Cut Areas 34

Single-Storied Stands 34

Two-Storied Stands 37

Three-Storied Stands 38

Multi-Storied Stands 40

Modifications to Cutting Treatments Imposed by

Spruce Beetles 40

Multiple-Use Silviculture 42

Water 42

Wildlife 42

Recreation and Esthetics 43

THE LODGEPOLE PINE TYPE 43

CHARACTERISTICS OF THE TYPE 43

PAST CUTTING HISTORY 44

DAMAGING AGENTS 46

Windfall 46

Insects 47

Diseases 47

NATURAL REGENERATION REQUIREMENTS 49

Seed Supply 49

Flowering and Fruiting 49

Cone Bearing Age 49

Cone Characteristics 50

Time of Seedfall 50

Production and Periodicity 51

Seed Quality 51

Dispersal 51

Source 52

Viability 52

Seed Losses 53

Factors Affecting Germination 53

Factors Affecting Initial Survival and Seedling Establishment 53

Initial Root Growth 54

Seedbed Type 54

Serotinous Cones 54

Nonserotinous Cones 55

Climate 55

Light and Solar Radiation 55

Temperature 55

Moisture 56

Soil 56

Diseases 56

Animal Damage 57

Ground Vegetation 57

SITE QUALITY 57

Conventional Determination 57

Determination from Soil and Topography 58

GROWTH AND YIELD 58

Growth of Immature Stands 59

Number of Stems 59

Diameter 59

Height 60

Basal Area 60

Volume 61

Crown Size 61

Volume Tables 61

Yields of Unmanaged Old-Growth Stands 61

Yields of Managed Stands 62

SILVICULTURE AND MANAGEMENT OF OLD GROWTH 63

Regeneration Silviculture 63

Clearcut Areas 63

Management with Advanced Reproduction 63

Management with Reproduction Following Cutting 63

Management for Artificial Regeneration 65

Partial Cut Areas 66

Single-Storied Stands 67

Two-Storied Stands 69

Three-Storied Stands 70

Multi-Storied Stands 72

Modification to Partial Cutting Practices Imposed

by Disease and Insect Problems 73

Cutting to Save the Residual 73

Slash Disposal and Seedbed Preparation 74

Multiple-Use Silviculture 74

Water 74

Wildlife 76

Recreation and Esthetics 76

MANAGEMENT OF YOUNG GROWTH 76

Stand Description 76

Thinning Practices 77

WHAT DO WE NEED TO KNOW 77

LITERATURE CITED 78

SILVICULTURE OF SUB ALPINE FORESTS
IN THE CENTRAL AND SOUTHERN
ROCKY MOUNTAINS:
The Status of Our Knowledge

Robert R. Alexander

Timber management research in the subal-
pine forests of the central and southern Rocky
Mountains has provided a large body of knowl-
edge on the silvics, silviculture, and manage-
ment of forest tree species during the past 50 or
more years. Research results and observations
have been presented as individual articles in a
variety of publications. Furthermore, a few
summary writeups for individual species have
been published for specific areas of research.
Included are (1) silvical characteristics (Alex-
ander 1958a, 1958b; Strothmann and Zasada
1957; Tackle 1961a; U.S. Department of Agri-
culture [USDA] 1965), (2) regeneration require-
ments (Roe et al. 1970), (3) planting procedures
(Ronco 1972), (4) partial cutting practices
(Alexander 1972, 1973), and (5) general bib-
liographies (Christensen and Hunt 1965, Ronco
1961a, Tackle and Crossley 1953). In Canada,
summary publications on regeneration, silvics,
silviculture, and management have been pre-
pared by Armit (1966), Dobbs (1972), and
Smithers (1961).

Much of the existing knowledge is still not
being used by land managers, however, because
it is either not readily available or not in a form
and language that can be easily understood. It is
the purpose of this document, therefore, to as-
semble in one place a comprehensive summary
of available knowledge on timber management
applicable to Rocky Mountain subalpine
forests. Included are (1) past research done in
the central and southern Rocky Mountains, (2)
work done elsewhere, but corroborated by ob-
servations in the central and southern Rockies,
and (3) research done elsewhere, where similar
information is lacking for subalpine forests.
From these facts, ideas, and observations,
guidelines are developed to answer the question
"to what extent are we now able to recommend
timber management practices to meet a variety
of uses." The report is intended specifically as a
field guide for professional foresters and land
managers who are responsible for prescribing
and supervising the application of silvicultural
treatments in the woods.

In the following sections, the report will cover
(1) the ecology and resource of the subalpine,
i and (2) the silvics, silviculture, and manage-

ment of (a) the Engelmann spruce (Picea en-
gelmannii Parry)- subalpine fir (Abies
lasiocarpa (Hook.) Nutt.) type, and (b) the
lodgepole pine (Pinus contorta Dougl.) type.
The spruce-fir and lodgepole pine types have
been handled in detail separately. There is some
repetition of information common to both types,
but each type was handled separately to facili-
tate the use of available information and rec-
ommended practices by foresters and land
managers. Major emphasis is placed on the sil-
viculture and management of old-growth, and
the establishment of new stands.

Rocky Mountain Douglas-fir (Pseudotsuga
menziesii var. glauca (Beissn.) Franco) and
quaking aspen (Populus tremuloides Michx.)
also occur in the subalpine, but their ecology,
silviculture, and management are described in
another report on the mixed conifers of the
Southwest.

THE ROCKY MOUNTAIN SUBALPINE
ECOLOGY

The subalpine is here defined as the highest
forested area in the States of Wyoming, Col-
orado, and northern New Mexico (fig. 1). It may
occur as low as 7,000 ft elevation in northern
Wyoming to as high as 12,000 ft in northern New
Mexico. These subalpine forests occupy what
most ecologists call the subalpine zone (9,000 ft
to timberline) and the upper montane zone
(7,500 to 9,000 ft).

Habitat Conditions

CLIMATE

The continental climate of the central and
southern Rocky Mountains is influenced by
three principal air masses: (1) Storms move
into the Rocky Mountains from the Pacific
Ocean during winter and early spring, carrying
relatively large amounts of moisture which are
released on the western slopes as the air masses
rise over the mountains (Johnson and Cline

■ Engelmann spruce
subalpine fir

Lodgepole pine
I

Figure 1. — Distribution of
spruce-fir and lodgepole pine
in the central and southern
Rocky Mountains.

1965, Marr 1961, USDA 1941). Only small
amounts of moisture fall on the east slopes.
These same storm fronts from the west pass too
far north during the summer to provide much
moisture. (2) Snowfall also occurs when polar
continental air moves south parallel to and east
of the Front Range during the winter and inter-
rupts the normal westerly flow (Marr 1961). (3)
Normally, the warm, moist air from the Gulf of
Mexico moving upslope provides moisture
along the east slope of the Rockies during the
spring and early summer, but at elevations
below the subalpine zone (Marr 1961). However,

when the storm track from the west moves
south through northern New Mexico and com-
bines with or causes a northward flow of the
Gulf air, the higher southern and eastern Rocky
Mountains receive moisture (Johnson and Cline
1965). In addition, convective thunderstorms
release some moisture in the high mountains
during the summers.

The diverse topography in the Rocky Moun-
tains results in various microclimates in the
subalpine that change significantly over short
distances. In general, temperature decreases
and precipitation increases with an increase in
elevation (Daubenmire 1943). Climatic records
for subalpine areas are mostly from valley sta-
tions, but a few representative records for
forested areas are provided by Baker (1944),
Bates (1924), Haeffner (1971), and Marr et al.
(1968).

The climate of the subalpine can be classified
as cool and humid, with long, cold winters and
short, cool summers (Alexander 1958a, Marr
1961, Thornthwaite 1948, Wilm and Dunford

1948). Mean annual temperature is below 35° F,
and frost can occur any month of the year. Pre-
cipitation is usually greater than 24 inches an-
nually. Most precipitation is received as snow-
fall, although the San Juan Mountains of south-
western Colorado and the mountains of north-
ern New Mexico receive considerable summer
rainfall. Winds are predominantly from the
west, and may be highly destructive (Alexander
1954, 1964; Alexander and Buell 1955; Dauben-
mire 1943).

GEOLOGY AND RELIEF

With the exceptions noted below, the Rocky
Mountains are anticlinal structures with igne-
ous and metamorphic cores (Eardley 1962,
Thornbury 1965).

The Absaroka Mountain Range in northwest-
ern Wyoming extends in a north-south direction
about 80 miles with an average width of 50 miles.
It is not a linear uplift, but a broad plateau of
volcanic breccia and basalt that has been deeply
eroded leaving isolated, rugged mountain
peaks. Glacial erosion has strongly etched the
steep walls surrounding the mountain peaks
(Eardley 1962, Fenneman 1931).

The Bighorn Mountains of north central
Wyoming are an isolated spur of the Rocky
Mountains. They are characterized by a central
core of Precambrian granites and schists partly
covered on the north and south by arched for-
mations of sedimentary conglomerates that
form elevated plateaus. Steeply inclined
sedimentary strata flank the core on the east
and west (Bowman 1911, Fenneman 1931).

The Wind River Mountains of western Wyo-
ming are characterized by a central core of Pre-
cambrian crystalline rock. The subsummit up-
lands consist of granites. Older sedimentary
rocks flank the mountains on the northeast side
as high as 9,000 to 10,000 ft. Further to the east
are foothills of sedimentary rock (Eardley 1962,
Fenneman 1931).

The Front Range of the Rocky Mountains ex-
tends in a north-south direction from the Arkan-
sas River in Colorado through the Medicine Bow
Mountains in southern Wyoming (Thornbury
1965). It is characterized by a central core of
Precambrian granites, schists, gneisses, and
dolomites that may be largely concealed in
some areas by glacial drift (Curtis 1960, Mears
1953, Oosting and Reed 1952, Thornbury 1965).
Sedimentary rocks are locally present, but are
not very important (Retzer 1962).

The plateaus of western Colorado consist of
sedimentary strata that have been pushed up-
ward without folding over a central core of Pre-
cambrian granites. The granite rocks are ex-

posed where rivers have dissected the sedimen-
tary rock. Masses of igneous rock — basalt,
andesite, and rhyolite — protrude through the
sedimentary mantle in places to interrupt the
plateau feature of this area (Bowman 1911,
Eardley 1962, Fenneman 1931).

The San Juan Mountains of southwestern Col-
orado are distinct from other mountain ranges
in Colorado because they are predominantly
volcanic lavas and tuffs over sedimentary rock
(Cross and Larson 1935, Larson and Cross 1956).
These mountains were carved by both glacial
and water erosion from the volcanic mantle
whose original surface had little relief (Fenne-
man 1931, Mather 1957). Precambrian granites
are locally abundant (Stevens and Ratte 1964).
The Jemez Mountains of north central New
Mexico are an extension of the San Juan Moun-
tains.

The Sangre de Cristo Range in southern Col-
orado and northern New Mexico resembles the
Front Range. These mountains consist of a steep
north-south anticlinal uplift of intrusive Pre-
cambrian granites flanked by sedimentary
shales, sandstones, limestones, and conglomer-
ates to the east and west that occasionally over-
reach the crest (Eardley 1962, Fenneman 1931).

SOILS AND LANDFORMS

There is only limited knowledge of the soils
and landforms of the subalpine. Soils are young,
and both soils and landforms complex. General
descriptions and typical soil profile charac-
teristics are given by Johnson and Cline (1965)
and Retzer (1956, 1962), but the basic informa-
tion on soils and landforms needed to determine
the capability and suitability of forest land for
different management activities is not availa-
ble.

In the lower subalpine below 9,500 ft eleva-
tion, and in the upper montane, soil parent mat-
erials are varied and mixed. Glacial deposits,
alluvial fan sediments, stream alluvium, and
materials weathered in place from country rock
predominate. Minor deposits of aeolian sedi-
ments occur locally. Crystalline rocks such as
granite, gneiss, schist, granodiorite, and rhyol-
ite are the principal bedrocks. Of the great soils
groups of major importance, Grey Wooded soils
are the most extensive and occur on all aspects.
Brunizems are most frequently found under
mixed grasslands and open timber on south
slopes. Chestnut soils occur largely on south
slopes at lower elevations. Brown Forest soils
are found under open timber, on stream ter-
races, or alluvial fans, on all except north
slopes. Humic Gley soils occur extensively in
poorly drained upper ends of stream valleys in

association with Bog soils. Lithosols are found
whenever bedrock occurs near the surface
(Johnson and Cline 1965).

In the upper subalpine above 9,500 ft, soil par-
ent materials also vary according to the charac-
ter of the bedrock from which they originated.
Crystalline granitic rocks predominate, but
conglomerates, shales, sandstones, basalts, and
andesites commonly occur throughout the reg-
ion. Most valleys have been glaciated, and gla-
cial deposits are common. Of the great soils
groups, Brown Podzolic and Classic Podzol soils
occur extensively on all aspects. Groundwater
Podzols are found in the more poorly drained
areas. Grey Wooded soils are found where
timber stands are less dense and parent materi-
als finer textured. Brown Forest soils occur
mostly at the lower margins of the upper subal-
pine, along stream terraces, and valley side-
slopes. Lithosols, Bog, and Humic Gley soils
occur under the same conditions as in the lower
subalpine (Johnson and Cline 1965).

Vegetation

The diversity of habitats in the central and
southern Rocky Mountain subalpine forests has
long been recognized by foresters and
ecologists, but the basic biological and ecologi-
cal information needed to understand the vege-
tation associations that make up these forests,
their requirements, and responses to manage-
ment practices is limited. The early work of
Rydberg (1915, 1916) provides a general and
historical background as well as some informa-
tion on specific geographical areas, and Bates
(1924) discussed the general relationships of
forest types.

LIFE ZONES

Altitudinal-vegetation zones have been a
common way of differentiating vegetation
(Daubenmire 1943, 1946, 1969; Marr 1961). In
addition, there is a geographical zonation of tree
species in the Rocky Mountain subalpine.

In the mountains of northern Wyoming, sub-
alpine forests grow at elevations between 7,000
and 10,500 ft. Lodgepole pine is the principal
species, but there are extensive stands of En-
gelmann spruce and subalpine fir above 9,500 ft.
Common associates are aspen at all elevations,
and Rocky Mountain Douglas-fir below 8,000 ft.
Minor species include limber pine (Pinus flex-
ilis James) and whitebark pine (Pinus albicaulis
Engelm.)

In the mountains of southern Wyoming and
north and central Colorado, subalpine forests

are found between 8,000 and 11,500 ft elevation.
Engelmann spruce and subalpine fir are the
principal species above 9,000 ft on north-facing
slopes and above 10,000 ft on all other slopes
(Dix et al.2, Langenheim 1962, Marr 1961.)
Lodgepole pine covers extensive areas between
8,000 and 10,500 ft, but reaches maximum de-
velopment on south- and west-facing slopes be-
tween 9,000 and 10,000 ft elevation (Dix et al.2).
At lower elevations, it occurs in the Douglas-fir
type (Daubenmire 1943). The characteristic
zonal pattern of lodgepole pine is attributed
primarily to moisture at lower elevations and
temperature at higher elevations (Tackle 1965).
Aspen also occupies extensive areas between
7,500 to 10,500 ft (Langenheim 1962, Marr 1961).
Aspen occurs in nearly pure stands on all as-
pects between 8,000 and 9,000 ft, and on south
slopes to 10,500 ft (Dix et al.2). Above 9,000 ft
on north slopes it usually occurs as islands of
trees in grassland and shrubland (Langenheim
1962, Morgan 1969). Douglas-fir below 8,500 ft,
and limber pine and bristlecone pine (Pinus
aristata Engel.) at higher elevations are minor
components of these subalpine forests.

On the higher plateaus of western Colorado,
the altitudinal range of subalpine forests is re-
stricted by topography to between 9,000 and
10,500 ft. Spruce and fir are the principal
species, and aspen the most common associate
below 10,000 ft. Douglas-fir is the most im-
portant "minor" species, but limited areas of
lodgepole pine do occur.

In southwestern Colorado and northern New
Mexico, subalpine forests grow from 8,500 to
12,000 ft elevation. Spruce, subalpine fir, and
corkbark fir (Abies lasiocarpa var. arizonica
(Merriam) Lemm.) are the characteristic
species above 8,500 ft on north slopes and 10,000
ft on south slopes. Douglas-fir grows between
8,500 and 9,500 ft, but does not form pure stands.
In the Douglas-fir type, aspen and white fir
(Abies concolor (Gord. and Glend.) Lindl.) are
common associates and blue spruce (Picea
pungens Engel.) and southwestern white pine
(Pinus strobiformis Engel.) minor associates.

Throughout the Rocky Mountain subalpine,
the upper limits grade into alpine tundra
through an ecotone of Krummholz (Daubenmire
1943, Marr 1961, Patten 1963). Engelmann
spruce is the dominant Krummholz species
(Wardle 1968).

zDix, Ralph L., Ordel A. Steen, and Steven
Whipple. 1972. A progress report on approaches to a
classification scheme of subalpine forests of the southern
Rocky Mountains. (Unpublished report by the Colo. State
Univ. Dep. Bot. and Plant Pathol; copy on file with study
FS-RM-1201.27, Rocky Mt. For. and Range Exp. Stn., Fort
Collins, Colo.)

SUCCESSIONAL STATUS

In classifying mountain vegetation into eleva-
tional zones, most ecologists have considered
the Engelmann spruce-subalpine fir community
the climax vegetation above 9,000 ft, and
Douglas-fir climax in the upper montane. The
monoclimax theory proposes that all other
communities in the subalpine will eventually
converge into these two climaxes, which are
limited only by regional climate (Clements
1936). Vegetation, however, is a function of to-
pographic, physiographic, edaphic, and biotic
factors as well as climate. Not only spruce-fir
and Douglas-fir, but lodgepole pine and aspen
seem to form stable communities in various
habitats in the subalpine (Daubenmire 1943,
Langenheim 1962, Mason 1915a, Moir 1969).

Although climax forests are not easily dis-
placed by other vegetation, fire, logging, and
insects have played an important part in the
successional status and composition of spruce-
fir forests. Complete removal of a spruce-fir
stand by fire or logging results in such drastic
environmental changes that spruce and fir are
usually replaced by lodgepole pine, aspen, or
shrub and grass communities (Roe et al. 1970,
Stahelin 1943). The kind of vegetation initially
occupying the site usually determines the
length of time it takes to return to a spruce-fir
forest. It may vary from as few as 50 years if the
site is initially occupied by lodgepole pine or
aspen to as many as 300 years if grass is the
replacement community (fig. 2). However, the

factors that determine the kind of replacement
community are not fully understood (Bates
1917b, Marr 1961, Stahelin 1943). On the other
hand, attacks by spruce beetles (Dendroctonus
rufipennis (Kirby)) have usually resulted in a
change in the dominant element in the stand
from spruce to fir. Because of its larger size and
longer life, spruce eventually regains its dom-
inant position in the stand, only to be removed
again by spruce beetles.3

Most foresters and ecologists agree that
lodgepole pine is an aggressive pioneer and in-
vader, and its occurrence is largely due to fire
(Clements 1910, Stahelin 1943). There is less
agreement on its successional status. Foresters
consider lodgepole pine to be serai in stands that
are only a temporary occupant of the site. In
those situations, stands have either a mixed
overstory composition or contain appreciable
amounts of advanced reproduction of other
species such as spruce, fir, or Douglas-fir. If
mountain pine beetles (Dendroctonus pon-
derosae Hopk.) attack those stands, the larger
lodgepole pines are removed, thereby shorten-
ing the time required for climax species to oc-
cupy the site. On the other hand, many lodgepole
pine stands are the result of catastrophic fires,
and some areas have burned so often and so
extensively that large acreages are nearly pure

^Schmid, J. M., and T. E. Hinds. Regrowth of spruce-fir
stands following spruce beetle outbreaks. (Manuscript in
preparation at Rocky Mt. For. and Range Exp. Stn., Fort
Collins, Colo.)

SPRUCE - FIR CLIMAX

I \
VERY SLOW

LODGE POLE PINE

SPRUCE-FIR

ASPEN

SPRUCE-FIR

PROCESS

LODGPPOLF " ^ acdpm^ DRY PARK SUBALPINE

LOUbtKULt LODGEPOLE < J^l^ GRASSLAND GRASSLAND

VACC

NIUM.GRASSSFORBS

MOSS.GRASSa FORBS
t

LIGHT FIRE SEVERE FIRE

t t

PRE-FIRE SUBALPINE FOREST

Figure 2. — Succession in subalpine forest after fire (Stahelin 1943).

pine. In those situations, lodgepole pine is main-
tained on the area as a subclimax because there
is no seed for the normal climax species (Tackle
1961a, 1965). In other situations where
lodgepole pine is held on an area by either
natural or artificial means, it is also considered
stable. One example of a naturally stable
lodgepole community is along the east slopes of
the Front Range at lower elevations. Douglas-
fir, the climax species, does not reproduce itself
in stands dominated by lodgepole pine because
the sites are too dry (Moir 1969).

Aspen is also a pioneer species that becomes
readily established by means of vigorous root
suckers after disturbance (Baker 1925, Gifford
1966). It is generally considered a fire sub-
climax, successional to spruce and fir at higher
elevations (Stahelin 1943) and Douglas-fir at
lower elevations, although lodgepole pine may
be an intermediate occupant of the site. How-
ever, Baker (1925) considered aspen a climax
relative to management in its area of optimum
development in western and southwestern Col-
orado. In other areas, aspen appears stable
where there is either no conifer seed or the site
is too dry for these species to become estab-
lished.

Fire, insects, and logging have converted
Douglas-fir stands to lodgepole pine, aspen, and
grass and shrub communities in many places in
the upper montane.

HABITAT TYPES

It is obvious that forest vegetation in the sub-
alpine is not a simple mosaic that can be readily
classified by vegetation zones. Rather it con-
sists of a wide variety of integrated,
disturbance-induced forest communities, many
representing various stages of secondary suc-
cession that are difficult to treat except as de-
velopmental series related to either specific
climaxes or stable plant communities.
Daubenmire and Daubenmire (1968) define
these relatively stable plant communities as
habitat types, primarily on the basis of the rela-
tive reproductive success of trees because this
indicates which species will become self-
perpetuating dominants in the overstory.
Habitat types are considered the basic ecologi-
cal subdivisions of landscapes. Each has a dis-
tinctive potential as to successional stage, and is
recognized by a distinctive overstory-
understory combination (Daubenmire and
Daubenmire 1968).

In northern Idaho and eastern Washington,
Daubenmire and Daubenmire (1968) identified
21 habitat types, each with a distinct ecology.
Subalpine fir occurs in 8 habitat types, usually

as a major climax species, while spruce and
lodgepole pine occur in 12, where they are con-
sidered to be successional to whatever species
are climax in the particular habitat type. In
western Montana, Pfister et al. (1972) using the
same procedures, identified 30 habitat types.
Subalpine fir occurs in 14, usually as a major
climax species, while spruce and lodgepole pine
occur mostly as serai species in 15 and 19
habitat types, respectively. Furthermore, man-
agement implications are keyed to each habitat
type.

In the subalpine forests of Utah, Pfister (1972)
identified four habitat types. Subalpine fir oc-
curs in three as a major climax species. Spruce
is a major climax species in the one habitat type
where fir is missing, and a minor climax species
in two others. Lodgepole pine occurs in two
habitat types as a serai species. Regeneration
systems are keyed to habitat types.

There have been few attempts to classify sub-
alpine forest vegetation into habitat types in the
central and southern Rocky Mountains; our
knowledge of vegetation associations is frag-
mentary. Oosting and Reed (1952) recognized
one habitat type, Picea engelmannii-Vaccinium
scoparium, in the Medicine Bow Mountains of
southern Wyoming, but their study was con-
fined to a small area. Dye and Moir,4 described
the forest vegetation in spruce-fir forests near
Sierra Blanca peak in southern New Mexico, but
their observations were limited to a single
habitat type, Abies lasiocarpa-Ribes
spp. iSenecio sanguiosorboid.es . Moir (1969,
1972) working in lodgepole pine forests that he
considered to be climax along the east slope of
the Front Range, identified two habitat types,
Pinus contort a-Vaccinium myrtillus above 9,500
ft and Pinus contorta-Geraniumfremontii on the
drier slopes of the upper montane. Reed (1969)
developed a classification using Daubenmire's
procedures for the Wind River Mountains of
northwestern Wyoming that recognized the fol-
lowing five habitat types:

1. Pinus albicaulis-Potentilla diversifolia. A
topographic climax on upper elevation, ex-
posed sites.

2. Picea engelmannii-Vaccinium scoparium.
All upper slopes.

3. Abies lasiocarpa-Pyrola secunda. All
slopes, mid-elevation.

*Dye,A.J.,andW.H.Moir. 1972. Spruce-fir forests
at its southern distribution in the Rocky Mountains, New
Mexico. (Unpublished report by the Colo. State Univ. Dep.
Range Sci.; copy on file in project 1201 , Rocky Mt. For. and
Range Exp. Stn., Fort Collins, Colo.)

4. Pseudotsuga menziesii (var. glauca) -
Symphoricarpos oreophilis. Lower north-
and east-facing slopes.

5. Populus tremuloides-Symphoricarpos oreo-
philis. Lower south- and west-facing slopes.

Almedia (1970) in a study of lodgepole pine
understory vegetation in Wyoming, identified
the following plant communities:

1. Pinus-Vaccinium.

2. Pinus-Carex.

3. Pinus-Calamagrostis.

4. Pinus-Elymus.

He described the floristic composition, changes
in vegetation associated with grazing and suc-
cession, and the management implications in
terms of forage yields and carrying capacity for
each plant community.

Steen and Dix5 worked on a phytosociological
classification of subalpine forests in the
Medicine Bow Mountains of Wyoming, along
the Front Range, and in the San Juan Mountains
of Colorado. They tentatively identified the fol-
lowing vegetation associations:

1. Picea engelmannii-V accinium spp. All
slopes.

2. Picea engelmannii-Polemonium delicatum.
Upper slopes.

3. Picea engelmannii-Cardimine cordifolial
Mertensia ciliata. Moist lower slopes.

4. Pinus contorta-Pachistima myrsinites. Dry
mid to lower slopes.

5. Abies lasiocarpa-Carex geyeri/Pachistima
myrsinites. Drier midslopes.

6. Abies lasiocarpa-Moss spp. Dry midslopes.

7. Populus tremuloides-Symphoricarpos spp.
Dry lower slopes.

8. Populus tremuloides-Thalictrum fendleri.
Mid south-facing slopes.

9. Populus tremuloides-Festuca thurberi. Drier
upper south-facing slopes.

Wirsing,6 working on a classification of the
Medicine Bow Mountains of southern Wyoming
and using Daubenmire's procedures, has tenta-
tively identified the following habitat types:

'"Steen, Ordel A., and Ralph L. Dix. 1972. A pre-
liminary classification of subalpine forests in the south-
ern Rocky Mountains. (Unpublished report by the Colo.
State Univ. Dep. Bot. and Plant Pathol; copy on file with
study FS-RM-1201.27, Rocky Mt. For. and Range Exp. Stn.,
Fort Collins, Colo.)

"■Wirsing, John M. 1973. Forest vegetation in
southwestern Wyoming. M.S. thesis, 170 p. Wash. State
Univ., Pullman.

1. Populus tremuloides-Carex geyeri. Lower to
middle south slopes.

2. Picea engelmannii/Abies lasiocarpa-
Vaccinium scoparium. Mid to upper slopes.

a. Sibbaldia/Bistorta phase (weakly de-
fined).

b. Pinus c ont or ta-V accinium scoparium.
(community or serai type).

3. Picea engelmannii/Abies lasiocarpa-Carex
geyeri. Midslopes.

a. Pinus contorta-Carex geyeri. (community
or serai type).

4. Pinus flexilis-Hesperochloa kingii. Top-
ographic climax within PicealAbies habitat
type.

a. Koeleria cristata phase. Upper
southwest-facing slopes and ridgetops.

b. Pulsatilla ludoviciana phase. Drier,
upper southwest-facing slopes and
ridgetops.

5. Pinus ponderosa-Carex geyeri. Lower slopes.

a. Sedum lanceolatum phase. Drier lower
slopes.

b. Lupinus argenteus phase. Well-drained
lower slopes.

Habitat conditions in the central and southern
Rocky mountains are much more diverse. The
wise management of this resource will require a
common system of classifying all forest lands
into units of like biological potential as a means
of (1) recognizing plant associations, (2) deter-
mining what species grow together, how they
reproduce, and grow, and (3) anticipating their
response in terms of successional trends and
stability when subjected to different manage-
ment prescriptions. Furthermore, the vegeta-
tion classification should be integrated with
soils and landforms to provide capability and
suitability classes for a variety of uses.

THE RESOURCE
Area and Volume

The subalpine forests are the largest and most
valuable timber resource in Colorado and
Wyoming. They are less important in terms of
total commercial forest land and sawtimber
volume in New Mexico.

In Wyoming, lodgepole pine grows on about
half of the commercial forest land in the subal-
pine (table 1). Engelmann spruce and subalpine
fir are second in importance in land area, fol-
lowed by Rocky Mountain Douglas-fir and
aspen. However, spruce-fir forests contain the
largest volume of sawtimber in Wyoming.
Lodgepole pine is second, followed by Douglas-
fir and aspen (Choate 1963).

In Colorado, spruce-fir forests occupy only
about one-third of the commercial forest land,
but contain nearly 70 percent of the sawtimber
volume in the subalpine (table 1). Aspen ac-
counts for more of the commercial forest land
than either lodgepole pine or Douglas-fir, but
less sawtimber volume (Miller and Choate
1964).

In New Mexico, Rocky Mountain Douglas-fir
grows on about half of the commercial forest
land in the subalpine, but it seldom grows in
pure stands (table 1). Spruce and true firs oc-
cupy the second largest area of commercial
subalpine forests, followed by aspen. About 10
percent of the sawtimber volume is in aspen; the
remaining 90 percent is about equally divided
between spruce and the true firs, and Douglas-
fir (Choate 1966).

One of the features of the spruce-fir and
Douglas-fir forests throughout the Rocky
Mountain subalpine is the imbalance in age-
class distribution (table 2). The largest propor-
tion of area is in sawtimber-sized stands, and the
smallest in seedling and sapling stands. The im-
balance in age-class distribution is not as seri-
ous in lodgepole pine and aspen forests, but
many of the pole-sized timber stands are either
overmature or growing on sites that are not
likely to produce a sawtimber-sized tree.

The acreage, volume, and stocking class data
in tables 1 and 2 are only approximate. They are
based on Forest Survey estimates made more
than 10 years ago, and a recent study (Wikstrom
and Hutchison 1971) indicates that too much
area was included in the timber growing base
because of inadequate information on land a-
vailability, growth capacity, and land capability.
Furthermore, some of the area available and

suitable for timber growing is either technolog-
ically or economically unusable at the present
time (Wikstrom and Hutchison 1971).

Properties and Uses of Wood

Engelmann spruce is one of the lightest of the
important commercial woods in the United
States. The wood is generally straight grained,
has moderately small shrinkage, can be readily
air dried, and is a uniform color (McSwain et al.
1970). It is rated low in beam and post strength
and in shock resistance (USDA 1955). The wood
is soft and machines well for ordinary uses. It
has good nail-holding properties, glues well, and
is easy to work, but paint-holding properties are
only average. If sufficient time is allowed, the
lumber can be kiln dried without difficulty. The
heartwood and sapwood are not durable when
used under conditions favorable to decay.
Spruce is considered somewhat resistant to
preservative treatment; however, crossties
have been successfully pressure treated for
many years (Anderson 1956). Subalpine fir
wood is light in weight, low in bending and com-
pressive strength, moderately limber, soft, and
low in resistance to shock. Shrinkage of wood
is rated small to moderately large (USDA 1955).

The lumber of spruce is likely to contain many
small knots. Consequently, it yields only minor
amounts of select grades of lumber, but a rela-
tively high proportion in the common grades
(Mueller and Barger 1963). In the past, spruce
was used principally for mine timbers, railroad
ties, and poles. Today much of the lumber of
both spruce and fir is used in home construction
where high strength is not required, and for

Table 1. --Acreage and volume (International 1/4-inch log scale) of sawtimber on commercial forests
in the central and southern Rocky Mountains, by species and States

Spec i es

Col orado

Wyom

New Mexico

Ar i zona

South

Dakota

M acres

MM bm

M acres

MM bm

M acres

MM bm

M acres

MM bm M

acres

MM bm

Engelmann spruce
and t rue firs

3,393

33,260

847

9,541

525

5,257

110

2, 147

Ponderosa pine

2,3*17

3,783

992

2,072

4,334

16, 188

3,658

22,883

1 ,330

3,268

Doug 1 as- f i r

1 ,451

5,41 1

701

3,566

1 ,000

5,025

1 30

1 ,476

Lodgepole pine

2,068

6,024

1 ,802

5,798

White pines

139

472

166

1 ,256

640

186

Wh i te spruce

201

Aspen

2,79^

3,482

320

159

367

1 ,233

259

Total

12,275

52,731

4,853

22,632

6,269

28,343

3,977

26,951

1 ,534

3,716

Table 2. --Percentage of commercial forest land area in the central and southern Rocky Mountains,

by species, stocking classes, and States

Species and

stocking class Colorado Wyoming New Mexico Arizona South Dakota

Engelmann spruce and true firs:

Sawt i mber
Polet imber

Seedlings and saplings
Nonstocked

Ponderosa pine:

Sawt i mbe r
Po 1 et i mbe r

Seedlings and saplings
Nonstocked

Dougl as-f i r:

Sawt i mbe r
Polet imber

Seedlings and saplings
Nonstocked

Lodgepole pine:

Sawt i mber
Polet imber

Seedlings and saplings
Nonstocked

White pines:

Sawt i mbe r
Polet imber

Seedlings and saplings
Nonstocked

White spruce:

Sawt i mbe r
Polet imber

Seedlings and saplings
Nonstocked

81
lit
1
4

64
23
1

27
0.5
0.5

34
60
5
1

45
52
2
1

14
1.5
2.5

73
20
3
4

72
22
3
3

45
6.5
1.5

46
44
6
4

100

85
5

7.5
2.5

90
3.5

4.5

90
8.5

1.5

100

95
2.5
1

1.5

100

41.5
4.5
1

100

Aspen :

Sawt i mbe r
Polet imber

Seedlings and saplings
Nonstocked

7
80
13

18
57
16

49
43-5
7.5

44.5
49-5
6

prefabricated wood products. In recent years,
rotary cut spruce veneer has been used in
plywood manufacture. Other uses of spruce in-
clude specialty items such as violins and pianos
and in aircraft construction (Anderson 1956,
McSwain et al. 1970). Spruce and fir have not
been used much for pulp and paper, but their
pulping properties are excellent. Long fibers,
light color, and absence of resins permit them to
be pulped readily by the sulfite, sulfate, or
groundwood processes (Anderson 1956, USDA
1955).

Lodgepole pine wood is generally straight, but
uneven grained. The wood is moderately soft,
moderately weak in bending and edgewise
compression, moderately low in shock resis-
tance, easy to work, easy to glue, and average in
paint-holding ability. It holds nails or screws
moderately well, shrinks moderately, but sea-
sons easily. It is not durable under conditions
that favor decay. Lodgepole pine yields mostly
narrow boards and little select grades of
lumber, but a high proportion of Grade 3 Com-
mon or better (Kotok 1971).

Lodgepole pine was once used primarily for
railroad ties, mine timbers,and rough construc-
tion lumber. Today much of the lumber is used
in light frame construction, particularly as 2- by
4-inch, 8-foot studs. It is especially valued for
knotty pine paneling and cabinets because of its
uniform color, small tight knots, and dimpled
surface. Lodgepole pine is easily pressure
treated and is used extensively for fenceposts,
corral poles, and transmission and telephone
poles. Its pulping properties are good and it can
be readily pulped by the sulfate and ground-
wood processes (Kotok 1971).

THE SPRUCE-FIR TYPE
STAND CONDITIONS

Old-growth spruce-fir forests grow on a wide
range of sites with a great diversity of stand
conditions and characteristics. This diversity
complicates the development of silvicultural
systems needed to convert old-growth to man-
aged stands for a variety of uses. For example,
spruce-fir forests are the dominant elements in
a number of near-climax vegetation associa-
tions throughout the central and southern
Rocky Mountains, but they do not have the age-
class structure of true climax forests. Some
stands are clearly single-storied, indicating that
desirable spruce forests can be grown under
even-aged management. Others are two- or
three-storied, and multi-storied stands are not
uncommon (Alexander 1973, LeBarron and
Jemison 1953, Miller 1970). These later stands
may be the result of either past disturbances
such as fire, insect epidemics, or cutting, or the
gradual deterioration of old-growth stands as-
sociated with normal mortality from wind, in-
sects, and diseases. The latter circumstance is
especially evident in the formation of some
multi-storied stands. On the other hand, some
multi-storied stands appear to have originated
as uneven-aged stands, and are successfully
perpetuating this age-class structure.

The composition of spruce-fir forests varies
considerably with elevation. At mid elevations
(10,000 to 1 1,000 ft), these forests are frequently
pure spruce in the overstory with fir pre-
dominating in the understory. For example, in
the central Rocky Mountains spruce commonly
makes up 70 percent or more of the overstory
basal area, and fir from two-thirds to three-
fourths of the understory and advanced repro-
duction (Alexander 1957a, 1963; Hodson and
Foster 1910, Oosting and Reed 1952). This com-
position in relation to structure has developed
under natural conditions because spruce is
more exacting in its seedbed requirements and

less able to compete with fir under low light
intensities common to dense forests. Once es-
tablished, however, spruce lives longer than fir
and is less susceptible to disease (Alexander
1958a, 1958b). Exceptions are in stands attacked
by spruce beetles, where fir is the dominant
element in both the overstory and understory
(see footnote 3).

At higher elevations, spruce may form essen-
tially pure stands while at lower elevations
where sites are usually drier, the density of
spruce relative to fir may be low. In these latter
situations, lodgepole pine is frequently more
numerous in the overstory than spruce (see
footnote 2).

Advanced spruce and fir reproduction is
likely to be older than it appears because the
early growth of both is slow. Spruce commonly
takes from 20 to 40 years to reach a height of 4 to
5 ft, even under favorable conditions, whereas
under a dense canopy, spruces 4 to 6 ft tall
may be 75 or more years old (Oosting and Reed
1952). Spruce and fir reproduction suppressed
for long periods of time will respond to release,
however, and make acceptable growth (Alex-
ander 1973).

PAST CUTTING HISTORY

Limited areas of the original spruce-fir
forests were logged in the late 1800's to provide
fuel, lumber, and timbers for early mining
camps. Cutting on the National Forests dates
back more than 50 years, but until the 1950's
only relatively small quantities of timber were
harvested. Cutting has accelerated rapidly
since.

Most cuttings in spruce-fir forests before
1950 in the central and southern Rocky Moun-
tains were of a type that could be collectively
called "partial cuttings." They ranged from re-
moval of a few individual trees to removal of all
the larger, more valuable trees in the stand.
Seedbed preparation was usually limited to the
disturbance created by logging, and slash was
untreated or lopped. Most skidding was done
with horses.

In general, heavy partial cutting — usually
considered necessary to make logging
profitable — was not successful as a means of
arresting stand deterioration or increasing net
increment on residual trees. For example, re-
sidual stands of spruce-fir in Colorado suffered
heavy mortality when 60 percent of the original
volume was removed by individual-tree selec-
tion (Alexander 1956a, 1963) (fig. 3). Net incre-
ment was only about one-third of that in uncut
stands. Similar results followed heavy partial
cutting elsewhere in the central Rocky Moun-
tains (USDA Forest Service [USDA-FS] 1933),

Figure 3.— Individual-tree selection cutting that removed 60 percent of the volume in spruce-fir.
Blowdown losses were heavy because the original dense stand was opened up too much.
Fraser Experimental Forest, Colorado.

and in the northern Rockies (Roe and DeJar-
nette 1965). Even when mortality was not a
problem, heavy partial cutting left the older,
decadent stands in a shabby condition, with lit-
tle appearance of permanent forest cover.

Windfall, the principal cause of mortality, in-
creased as the intensity of cutting increased.
Low stumpage values and the generally scat-
tered pattern of windfall usually prevented sal-
vage of blowdown after partial cutting. Not only
was the volume of windthrown trees lost, but the
combination of down spruce and overstory
shade provided breeding grounds for spruce
beetles.

Partial cutting was successful — in the sense
that the residual stand did not suffer heavy
mortality — in some spruce-fir stands where
large reserve volumes were left in protected
locations. In one study in northern Idaho, wind-
fall losses were light after a partial cutting that
left a residual stand of 6,000 board ft (fbm) per
acre in a sheltered location on deep, well-
drained soil (Roe and DeJarnette 1965). On the
Grand Mesa National Forest in Colorado, where
spruce trees are relatively short and there are
no serious wind problems associated with to-
pography, few trees blew down when about 40
percent of the original volume was removed
from two-storied stands. In single-storied
stands, however, only about 30 percent of the

original volume could be safely removed. On the
other hand, heavier partial cutting that re-
moved 50 percent or more of the original vol-
umes per acre from spruce-fir forests in the dry
"rain shadow" of the Continental Divide on the
Rio Grande National Forest did not result in
blowdown to the residual stand. However, these
two-storied stands were growing on sites where
productivity was very low. Individual trees
were short, widely spaced, and therefore rela-
tively windfirm before cutting.

There are also numerous examples of early
cuttings — between 1910 and 1930 — on many
National Forests in Colorado where very light
partial cutting — removal of 10 to 15 percent of
the stand — did not result in substantial
windthrow of residual trees.

Although an overstory tends to favor fir re-
production over spruce, regeneration success
of spruce has been acceptable under a wide var-
iety of partial cutting treatments (Alexander
1963, Roe and DeJarnette 1965).

In the early 1950's harvesting shifted to
clearcutting. The first clearcuttings were in
narrow strips (200 to 400 ft wide) or small
patches, with little seedbed preparation or slash
disposal (fig. 4). Advanced regeneration was not
completely destroyed. In general, windfall loss-
es were less than after heavy partial cutting,
and the cutovers were usually adequately re-

Figure 4. — Clearcutting that removed 50 percent of the volume in narrow, alternate strips in
spruce-fir. Fraser Experimental Forest, Colorado.

stocked with a combination of surviving ad-
vanced and new reproduction (Alexander
1956a, 1957a, 1963, 1966d, 1968; Averill and An-
drews 1964). By the late 1950's, the common
practice was to clearcut in large blocks,
patches, or wide strips. These larger openings
were justified as being more effective in con-
trolling spruce beetles and in reducing logging
costs. Slash and cull material were either
broadcast burned, dozer-piled, or windrowed
and burned. Hazards from fire and insects were
reduced, but removal of all slash, cull material,
and residual trees left the seedbeds devoid of
shade, thereby creating a difficult microenvi-
ronment for the establishment of either natural
or artificial regeneration (Roe et al. 1970, Ronco
1970a). Furthermore, the destruction of ad-
vanced reproduction was usually an unneces-
sary loss of valuable growing stock.

Today, after nearly 20 years of harvesting
spruce-fir almost exclusively by clearcutting,
there is a shift in cutting practices to either
some form of partial cutting or a combination of
partial cutting and small cleared openings with-
out complete cleanup of slash and other logging
debris (Alexander 1973). This shift was neces-
sary because clearcutting large areas often (1)
resulted in adverse visual and environmental
impacts, (2) was incompatible with the objec-
tives of other forest uses, and (3) led to regener-
ation failures.

DAMAGING AGENTS
Windfall

Windfall is a common cause of mortality after
any kind of initial cutting in old-growth spruce-
fir forests, but partial cutting increases the risk
because the entire stand is opened up and there-
fore vulnerable. Windfall is usually less around
clearcuts because only the boundaries between
cut and leave areas are vulnerable, but losses
can be substantial if no special effort is made to
locate windfirm cutting unit boundaries (Alex-
ander 1964, 1967b).

While the tendency of spruce to windthrow is
usually attributed to a shallow root system, the
development of the root system varies with soil
and stand conditions. On medium to deep, well-
drained soils, trees have a better root system
than on shallow, poorly drained soils. Trees that
have developed together in dense stands over
long periods of time mutually protect each
other, and do not have the roots, boles, or crowns
to withstand sudden exposure to wind if opened
up too drastically. If the roots and boles are
defective, the risk of windthrow is increased.
The presence of old windfalls in a stand is a good
indicator of lack of windfirmness. Further-
more, regardless of the kind or intensity of cut-
ting, or soil and stand conditions, windthrow is
greater on some exposures than others (Alex-

ander 1964, 1967b, 1973). Exposures where
windfall risk is below average, above average,
or very high have been identified as follows:

Below Average

1. Valley bottoms, except where parallel to
the direction of prevailing winds, and flat
areas.

2. All lower, and gentle middle north- and
east-facing slopes.

3. All lower, and gentle middle south- and
west-facing slopes that are protected
from the wind by considerably higher
ground not far to windward.

Above Average

1 . Valley bottoms parallel to the direction of
prevailing winds.

2. Gentle middle south and west slopes not
protected to the windward.

3. Moderate to steep middle, and all upper
north- and east-facing slopes.

4. Moderate to steep middle south- and
west-facing slopes protected by consid-
erably higher ground not far to wind-
ward.

Very High

1. Ridgetops.

2. Saddles in ridges.

3. Moderate to steep middle south- and
west-facing slopes not protected to the
windward.

4. All upper south- and west-facing slopes.

The risk of windfall in these situations is in-
creased at least one category by such factors as
poor drainage, shallow soils, defective roots and
boles, and overly dense stands. Conversely, the
risk of windfall is reduced if the stand is open
grown or composed of young, vigorous, sound
trees. All situations become very high risk if
exposed to special topographic situations such
as gaps or saddles in ridges at higher elevations
to the windward that can funnel winds into the
area.

Insects

Keen (1952) lists a large number of insect
pests of Engelmann spruce. Of these, the spruce
beetle (Dendroctonus rufipennis (Kirby)) is the
most serious. It is restricted largely to mature
and overmature spruce, and epidemics have oc-
curred throughout recorded history (Hopkins
1909, Massey and Wygant 1954). The most
damaging recorded outbreak was in Colorado
from 1939-51, when beetles killed nearly 4 bill-
ion fbm of standing spruce (fig. 5). Damaging
attacks have been largely associated with ex-
tensive windthrow, where down trees have pro-
vided an ample food supply needed for a rapid
buildup of beetle populations (Massey and
Wygant 1954, Wygant 1958). Cull material left
after logging has also started outbreaks, and
there are examples of heavy spruce beetle
populations developing in scattered trees
windthrown after heavy partial cutting. The

Figure 5. — Beetle-killed spruce stand. White River National Forest, Colorado.

beetle progeny then emerge to attack living
trees, sometimes seriously damaging the re-
sidual stand. Occasionally heavy spruce beetle
outbreaks have developed in overmature stands
with no recent history of cutting or windfall, but
losses in uncut stands that have not been sub-
jected to catastrophic windstorms have usually
been no greater than normal mortality in old
growth (Alexander 1973).

Spruce beetles feed and breed in the phloem
layer. The first evidence of attack is the red
boring dust from entrance holes that usually
accumulates in bark crevices on the boles and
around the bases of infested trees. The needles
of killed trees usually turn a yellowish green
and fall about 1 year after attack, but they may
remain green until the second year (Schmid and
Beckwith 1971).

Overmature trees are attacked first, but if an
infestation persists, beetles will attack and kill
smaller diameter trees after the larger trees in
the stand are killed. In the central Rocky Moun-
tains, susceptibility of spruce stands in relation
to location decreases in the following order: (1)
trees in creek bottoms, (2) better stands on
benches and high ridges, (3) poorer stands on
benches and high ridges, (4) mixed stands, and
(5) immature stands (Knight et al. 1956, Schmid
and Beckwith 1971). Analysis of past infesta-
tions suggests the following characteristics are
associated with potential outbreaks: (1) single-
or two-storied stands, (2) high proportions of
spruce in the overstory, (3) basal area of 150 ft2
per acre or more in the older and larger trees,
and (4) an average 10-year periodic diameter
growth of 0.4 inch or less (see footnote 3).

Natural factors such as nematodes, insect
parasites and predators, and woodpeckers nor-
mally maintain beetle populations at low
levels, but generally fail to control populations
under outbreak conditions. Extremely low
temperature can eliminate beetle infestations,
however, if the insect has not developed cold-
hardiness. Temperatures of -15° F under the
bark will kill nearly all adults, while -30° F will
kill the larvae (Schmid and Beckwith 1971).
Chemical control is expensive and only a hold-
ing action until potentially susceptible trees can
be disposed of. In infested stands, or those with
potential beetle problems, felling and salvaging
attacked or susceptible trees, and disposing of
green cull material is the most effective sil-
vicultural control. Partial cutting that removes
the larger overmature trees and releases the
younger trees is another way to reduce potential
insect problems in stands with a good stocking
of trees in the smaller diameter classes. "Trap
trees" intentionally felled prior to beetle flight
are highly attractive, and often provide an ef-
fective way of concentrating and trapping

spruce beetles (Nagel et al. 1957). After the bee-
tles enter the downed logs, they are usually sal-
vaged, but may be chemically treated or burned
(Schmid and Beckwith 1971). Lethal traps in
which cacodylic acid is used to prevent brood
development in trap trees appears to be a poten-
tially useful refinement to the regular trap-tree
approach (Buffam et al. 1973).

The western spruce budworm (Choristoneura
occidentalis Freeman) is another potentially
dangerous insect attacking Engelmann spruce
(Whiteside and Carolin 1961). Subalpine fir is
attacked by several groups of insects (Keen
1952), the most important of which are the west-
ern spruce budworm and the fir engraver
(Scolytus ventralis Lee). The western balsam
bark beetle (Dryocoetes confusus Sw.) may at
times be very destructive locally (Stevens
1971).

Diseases

The most common diseases in spruce-fir
stands are caused by wood-rotting fungi that
result in loss of volume (Hinds and Hawksworth
1966, Hornibrook 1950) and predispose trees to
windthrow and windbreak (Alexander 1964,
1967b). In a recent study of cull indicators and
associated decay in Colorado, Hinds and
Hawksworth (1966) identified the major root
and butt fungi in mature to overmature Engel-
mann spruce as Fomes nigrolimitatus (Rom.)
Engel., Pholiota alnicola (Fr.) Singer, Polyporus
tomentosus Fr., Corticium radiosum (Fr.) Fr.,
and Coniophora puteana (Schum ex. Fr.) Karst.
Trunk rots which caused 88 percent of the decay
were associated with Fomes pini (Fr.) Karst,
Stereum sanguinolentum (Alb. and Schw. ex.
Fr.) Fr.,S. sulcatum Burt. andS. chailletii (Pers.
ex. Fr.) Fr. Hinds and Hawksworth (1966) have
provided a means of estimating defect in stand-
ing spruce based on the average amount of cull.
Most cull was associated with specific indi-
cators that were grouped into three classes. Cull
deductions for these indicators are shown
below:

Decay as a proportion
Indicator type of gross volume

(Percent)

1. Fomes pini knots or 81
sporophores

2. Broken tops with adjacent dead 24
brooms

3. Basal wounds, dead broom io
rusts, dead leader, frost cracks,

forks, joined at base, spiketop
on trunk wounds

Decay in relation to age, diameter, and site
quality have been determined for subalpine fir
in Colorado (Hinds et al. 1960). Important root
and butt rot fungi are Corticium radiosum (Fr.)
Fr., Coniophora puteana (Fr.) Karst, Armillaria
mellea (Fr.) Quel., Coniophora olivacea (Fr.)
Karst, Pholiota squarrosa (Fr.) Kummer, and
Polyporus tomentosus Fr. Stereum sanguinolen-
tum (Fr.) Fr., Fomes pini (Fr.) Karst, and S.
chailletii (Fr.) Fr. are responsible for most
trunk rot.

Spruce broom rust (Chrysomyxa arcto-
staphyli Diet.) and fir broom rust
(Mel amps or ell a caryophyllacearum Schroet.)
are also common in spruce-fir forests. They
cause bole deformation, loss of volume,
spiketops, and windbreak, and provide infection
courts for decay fungi (Peterson 1963).

NATURAL REGENERATION
REQUIREMENTS

A supply of viable seed, a suitable seedbed,
and an environment compatible with germina-
tion and seedling establishment are the basic
elements necessary for successful regenera-
tion (Roe et al. 1970). If one of these elements is
missing, regeneration fails (fig. 6).

Seed Supply

FLOWERING AND FRUITING

Male flowers of both spruce and fir ripen and
pollen is wind disseminated in late spring or
early summer. Cones mature and seed ripens
from late August to early October the first year
(Alexander 1958a, 1958b; USDA-FS 1948).

CONE-BEARING AGE

Although cones have been observed on open-
grown spruces and firs when they are about 4 to
5 ft tall and from 15 to 40 years old, seed produc-
tion does not become significant until the trees
are larger and older. The most abundant crops
in natural stands are produced on healthy, vig-
orous, dominant trees 100 to 250 years old
(Alexander 1958a, 1958b; USDA-FS 1948).

TIME OF SEEDFALL

Natural seedfall in spruce stands begins in
early September and continues through the
winter, but only minor amounts of seed fall be-
fore mid-September. In 1 year on the Fraser

NATURAL REPRODUCTION TRIANGLE

TYPE INSOLATION
Duff and litter Light intensity

PHYSIOGRAPHIC SITE
Aspect
Elevation
Slope

Figure 6. — Factors affecting spruce seedling survival and
establishment (Roe et al. 1970).

Experimental Forest in Colorado, about half of
the total sound seed was released before the end
of September. 7 In a good seed year in the Inter-
mountain Region, from two-thirds to three-
fourths of the total sound seed was released by
October 20 on two areas, but only about one-
third of the total sound seed was released by
that date on a third area (Roe 1967).

Subalpine fir seedfall begins in early Sep-
tember and is usually completed by the end of
October (Alexander 1958b).

CONE-CROP PREDICTABILITY

The ability to estimate the size of the cone
crop well in advance would be important to the
forest manager, because it would provide the
basis for scheduling harvesting operations,
seedbed preparation for natural reproduction,

'Unpublished data on file with study FS-RM-1201.24,
Rocky Mt. For. and Range Exp. Stn., Fort Collins, Colo.

and seed collection (Dobbs 1972). Several ways
have been suggested as a means of estimating
potential cone crop size for other species, but no
method has been developed for spruce.

PRODUCTION AND PERIODICITY

Engelmann spruce is rated a moderate seed
producer, and seed crops vary considerably
from year to year. Infrequent seed crops means
that natural reproduction cannot be expected
every year.

In an early study in Colorado, average annual
seed production on the White River Plateau for
an 18-year period (1914-31) was 83,000 sound
seeds per acre, while on the Uncompaghre
Plateau, annual seed production for a compara-
ble 15-year period (1914-28) averaged 350,000
sound seeds per acre (USDA-FS 1933). Good
seed crops (100,000 or more sound seeds per
acre) were produced on the White River only at
5- to 7-year intervals, with complete failures
about every 2 years. On the Uncompaghre, good
crops were produced every 2 to 4 years, with
complete failures at about 3-year intervals. In a
study on the Fraser Experimental Forest in Col-
orado, annual seed production averaged only
32,100 sound seeds per acre during the period
1956-65 (Alexander 1969). Only one good and
two moderate (50,000 to 100,000 sound seeds per
acre) crops were recorded. Seed production was
also observed on five National Forests in Col-
orado for the period 1961-67.In one year (1967) a
bumper seed crop was produced on all areas.
Seed production, varying from 845,000 to
5,340,000 sound seeds per acre, was the highest
ever recorded in the central Rocky Mountains
(Ronco and Noble 1971). In the other years of the
study, some seed was produced each year, but
good crops occurred only once in 4 to 5 years on
three of the areas, and in 2 of 6 years on the other
two areas (Ronco 1970b). Furthermore, these
good crops did not occur in the same years on all
areas.

Similar results for spruce have been reported
from the northern Rocky Mountains. Boe (1954)
analyzed cone crops in Montana between the
years 1908 and 1953. He reported that 22 crops
observed during the 45-year period west of the
Continental Divide were rated as 5 good, 8 fair,
and 9 poor. East of the Divide, seed production
was poorer; only 2 good, 4 fair, and 15 poor crops
were reported for a 21-year period. Seed pro-
duction in 1952 in western Montana was esti-
mated at 953,000 sound seeds per acre (Squil-
lace 1954), but this was in a bumper year. Seed
crops in the other 4 years of record were fail-
ures. Seed production in a good year (1964) on
three areas in the Intermountain Region ranged

from 200,000 to 2 million sound seeds per acre
(Roe 1967). Seed production in the other 4 years
of observation were also rated failures.

Subalpine fir seed production has not been
studied in the central and southern Rocky
Mountains. Elsewhere in the Rocky Mountains,
it has been rated a prolific seed producer, with
good crops borne every 3 years with light crops
in between (LeBarron and Jemison 1953,
USDA-FS 1948). In one study in the Cascade
Mountains of Washington and Oregon, fir pro-
duced light to very heavy cone crops about
every 3 years with failures in the intervening
years (Franklin 1968). Observations in the cen-
tral Rocky Mountains indicate that fir is not that
good a seed producer, and failures are more
common than good seed years.

SEED QUALITY

Variability in seed quality accentuates dif-
ferences in seed production. The proportion of
sound seed is usually highest in years of highest
seed production. In the central Rocky Moun-
tains, 70 to 90 percent of the seed produced in
the bumper seed year of 1967 was sound.8 In
years of moderate to good crops, 30 to 50 per-
cent were sound, and in other years, 10 to 30
percent were sound.

DISPERSAL

Spruce seed is light, averaging about 135,000
seeds per pound, and disperses long distances. In
one study in Colorado,8 as many as 96,000 sound
seeds per acre were dispersed as far as 400 ft
from standing timber into a clearcut block. In
western Montana, significant quantities of seed
(60,000 sound seed per acre) were dispersed as
far as 600 ft from timber edge into a large clear-
cut block (Squillace 1954). These dispersals oc-
curred only during a bumper (1952) and record
(1967) seed year, however (Ronco and Noble
1971, Squillace 1954). Seedfall into cleared
openings in Colorado that varied from about 130
to 850 ft wide, diminished as distance from seed
source increased; most seeds fell within 100 to
150 ft of standing timber (Alexander 1969,
Ronco 1970b, Ronco and Noble 1971). Prevailing
winds influenced the pattern of seedfall on
areas larger than 200 ft wide. In years of sig-
nificant seed production, about half of the total
number of sound seeds dispersed fell within 150
ft of the windward timber edge. Seedfall then

"Unpublished data on file with study FS-RM-1201.13,
Rocky Mt. For. and Range Exp. Stn., Fort Collins, Colo.

diminished steadily as distance increased to
about two-thirds of the way across the openings.
At this distance the average number of sound
seeds falling was about 10 percent of the
number released in the uncut stands. Beyond
this point, seedfall gradually increased toward
the leeward timber edge (fig. 7).

In the Intermountain and Northern Rocky
Mountain Regions, spruce seed dissemination
on four areas in good seed years also diminished
from timber edge into openings (Roe 1967).
Seed was dispersed in significant quantities (0.5
to nearly 5 percent of the total released under
the uncut stand) as far as 660 ft where a heavy
seed source was present, (193 ft2 of basal area
in Engelmann spruce trees 10.0 inches d.b.h.
and larger), but the dispersal winds were too
variable to show definite directional patterns.
Lighter seed sources, 70 ft2 of basal area or
less, dispersed fewer seeds for shorter dis-
tances. Smaller openings are required with
lighter seed sources to insure adequate seedfall
on all parts of the opening, otherwise the areas

Direction of prevailing windl

SEEDS (THOUSAND
PER ACRE)

340
320
300
2SO
260
240
220

_l_

_L_

beyond the reach of adequate natural seeding
must be artificially reforested (Roe 1967).

Just because seed can be dispersed long dis-
tances is not enough. Large quantities of seed
will not restock harsh or incompatible environ-
ments (Roe et al. 1970). For example, seedfall
that averaged 1.8 million sound seeds per acre
over the entire opening on one area in Colorado
did not result in adequate restocking because of
unfavorable seedbeds and adverse environ-
mental conditions: intense solar radiation and
high temperatures, low temperatures and frost
heaving, and drying winds (Ronco and Noble
1971). The effective seeding distance, defined
by Roe et al. (1970) as the distance over which
sufficient sound seed is dispersed to stock an
area to an acceptable level under prevailing
conditions, is more meaningful than mere seed
dispersal distance.

A current study9 of field germination on the
Fraser Experimental Forest in Colorado has in-
dicated that, on north slopes under favorable
seedbed and environmental conditions (shaded,
mineral soil), at least 20,000 sound seeds per
acre are needed to provide 1,000 seedlings sur-
viving at the end of the first growing season.
That seedfall is not likely to occur beyond about
300 ft from a windward seed source except in
years of bumper seed production. Furthermore,
seedling mortality will continue to reduce initial
first-year stocking for at least 5 years. There-
fore, adequate restocking is not likely to result

"Unpublished data on file with study FS-RM-1201.20,
Rocky Mt. For. and Range Exp. Stn., Fort Collins, Colo.

UNCUT TIMBER
West

10 2.0 3 0 4.0 5.0

DISTANCE FROM WINDWARD TO LEEWARD
TIMBER EDGE (CHAINS)

7.0

UNCUT Tl«
East

1 Figure 7. — Total 10-year Engelmann spruce seedfall into clearcut openings in
relation to distance from windward timber edge.

from only one good seed crop. This suggests
that the maximum width of opening that can
restock over a period of years under favorable
conditions is about 450 ft or five to six times tree
height. On south slopes under the same seedbed
and environmental conditions, at least 100,000
sound seeds per acre will be required to provide
1,000 first-year seedlings. Effective seeding
distance is about 100 ft from the windward seed
source. On the other hand, on north slopes
200,000 sound seeds per acre will be required to
provide 1,000 first-year seedlings on unpre-
pared and unshaded seedbeds, while no amount
of seed will restock these seedbeds on south
slopes (see footnote 9). Under average condi-
tions in the Rocky Mountains, the distance of
effective seed dispersal is likely to be 150 ft or
less (Alexander 1969, Jones 1967, Roe and
Schmidt 1964, Ronco 1970b).

Effective seeding distance may be greater in
the northern than in the central Rocky Moun-
tains. In one study in northern Idaho, a
peripheral strip 660 ft wide around a large patch
cutting was restocked naturally (Roe and De-
Jarnette 1965). Roe et al. (1970) have suggested
that an effective seeding distance of 660 ft may
be possible on northerly aspects with about 200
ft2 of basal area in seed trees in the uncut
timber edge, but only 200 to 400 ft is likely on
south slopes. Effective seeding distances with a
light seed source, 70 ft- of basal area or less,
will vary from 0 to 200 ft on north slopes and 0 on
other aspects. They concluded that the longer a
favorable seedbed persists the greater the ef-
fective seeding distance.

Subalpine fir seed is larger than spruce, av-
eraging about 37,500 to the pound (Alexander
1958b, USDA-FS 1948). Practically all seed is
wind disseminated, but there are no data on dis-
persal distances.

SOURCE

There are several ways of providing a seed
source for both spruce and fir. In cleared open-
ings, the principal seed source is the trees left
standing around the perimeter of the opening.
Minor amounts of seed are available from the
smaller unmerchantable trees left on the area,
and some seed is also produced by the trees cut
on the area. On partially cut areas, the residual
trees are the principal seed source, but some
seed is produced by trees cut on the area. One of
the significant considerations in the kind of
seed source to leave is resistance to windthrow.
Situations and conditions where windfall risks
were high, above average, and below average
around the margins of cleared openings have
been identified in Colorado, and recommenda-

tions developed for locating windfirm bound-
aries on clearcut units (Alexander 1964, 1967b).
These recommendations have been modified to
identify the kinds of trees and residual volumes
that can be successfully retained in partial cut-
ting for different stand conditions and windfall
risk situations (Alexander 1973).

VIABILITY

The viability of spruce is rated both good (av-
erage germinative capacity is about 70 percent
the first year) and persistent (average germina-
tive capacity 30 to 50 percent after 5 years) if
stored properly (Alexander 1958a, USDA-FS
1948, Van Dersal 1938). Spruce does not nor-
mally require pretreatment to break dormancy,
and germinative capacity is not improved by
stratification (Curtis 1958). Under natural con-
ditions, seed overwinters under the snow and
germinates the following spring. Occasionally
some germination is delayed until the second
year (Ronco 1967, see also footnote 9).

Subalpine fir seed viability is rated only fair
(average germinative capacity is 38 percent)
and the vitality transient (Alexander 1958b,
USDA-FS 1948, Van Dersal 1938). However, ob-
servations and limited studies in the Rocky
Mountains indicate that germinative capacity is
often less than 30 percent (Shearer and Tackle
1960). Some lots of stored seeds exhibit embryo
dormancy, which can be broken by stratifica-
tion in moist sand or peat at 41° F for 60 days
(USDA-FS 1948). Under natural conditions, fir
seeds lie dormant under the snow and germi-
nate the following spring.

SEED LOSSES

Observations on the Fraser Experimental
Forest indicated that a substantial part of the
1972 spruce seed crop was lost before seedfall
to cone and seed insects.10 A number of cone
and seed insects of spruce and fir have been
identified by Keen (1958), but their relative im-
portance, frequency of occurrence, and the
magnitude of losses are not known.

Pine squirrels (Tamiasciurus hudsonicus
fremonti Audubon and Bachman) are a major
consumer of spruce and fir cones and seeds, as
evidenced by the large caches common to
spruce-fir forests. These caches have been the
principal source of seed for reforestation.

l0Personal communication with Daniel L. Noble,
Forestry Technician, Rocky Mt. For. and Range Exp. Stn.,
Fort Collins, Colo.

After seed is shed to overwinter under the
snow, small mammals are the principal source
of seed losses. The most important seedeaters
include deer mice (Peromyscus maniculatus
(Wagner)), red-backed mice (Clethrionomys
gapperi (Vigors)), mountain voles (Microtus
montanus (Peale)), and western chipmunks
(Eutamias minimus Bachman). All spruce-fir
forests support populations of these small
mammals, and any disturbance that initiates
understory plant succession favors a buildup of
populations, particularly if slash and other
down material is present to provide cover. Un-
doubtedly these mammals eat considerable
seed, but the magnitude of losses is not known
for the central and southern Rocky Mountains,
and results from studies elsewhere are conflict-
ing. In western Montana, for example, spruce
seedling success was little better on protected
than unprotected seed spots (Schopmeyer and
Helmers 1947). On the other hand, protection of
seed from rodents was essential to spruce and
fir regeneration success in central and southern
British Columbia (Prochnau 1963, Smith 1955).

Factors Affecting Germination

Viable seeds of spruce and fir that survive
overwinter normally germinate following
snowmelt in June or early July in the central
Rocky Mountains, when seedbeds are moist and
air temperatures at least 45° F. On the Fraser
Experimental Forest in Colorado, field germi-
nation of spruce seeds has ranged from 0 to 28
percent, depending upon seedbed, weather, and
aspect (see footnote 9).

Seedbed is one of the keys to spruce germina-
tion success (Roe et al. 1970). Germination is
usually better on exposed mineral soil than
other seedbed types because of more stable
moisture conditions (Clark 1969, Day 1964, Day
and Duffy 1963, Roe and Schmidt 1964,see also
footnote 9). Germination is often good on min-
eral soil with incorporated organic matter if a
constant supply of moisture is available (Clark
1969; Day 1963, 1964). Germination on burned
seedbeds has been variable. Success has been
associated with the severity of burn and the
depth of loose ash (Clark 1969, Roe et al. 1970,
USDA-FS 1943). The natural forest floor, duff,
litter, and undecomposed humus are generally
poor seedbeds even when moist because seeds
cannot absorb sufficient water to germinate
(Barr 1930, Smith 1955). Germination may be
high on decayed wood (Day 1964, Day and Duffy
1963), but without overhead shade many of
these seedlings die when the seedbed dries out
(Roe et al. 1970).

The effectiveness of the seedbed is influ-

enced by such factors as weather, shade, and
soil texture that operate primarily through their
effects on moisture and temperature. Dead
shade may increase germination by reducing
temperatures, thereby conserving moisture.
Low temperatures on shaded seedbeds in the
spring following snowmelt may delay germina-
tion, however, so that by the time seedbeds are
warm enough they are too dry. Germination can
also be delayed if precipitation is low or irregu-
lar in June or early July following snowmelt.
Exposed seedbed surfaces are rapidly dried out
and heated to high temperatures during periods
of clear weather. Few seeds can imbibe suffi-
cient water to germinate, and most newly ger-
minated seedlings are killed by either drought
or stem girdle (Day 1963, 1964; Roe et al. 1970).
If germination is delayed until the late summer
rains, the late-germinating seedlings are unable
to harden off before the onset of cold weather
(Ronco 1967, see also footnote 9). Ronco (1967)
also found that germination followed definite
storm periods.

Alexander and Noble (1971) studied the ef-
fects of amount and distribution of watering
treatments — selected to represent precipita-
tion patterns and temperatures likely to occur
at 10,500 ft elevation on the Fraser Experimen-
tal Forest in Colorado — on the germination of
spruce in the greenhouse. They concluded that,
under favorable seedbed and environmental
conditions: (1) more seedlings would emerge
with frequent showers than with one or two
larger storms when monthly precipitation is 1
inch or less, and (2) when monthly precipitation
averages 1 inch or more, germination is com-
pleted in a relatively short time with frequent
showers, whereas seedlings will emerge
throughout the growing season if precipitation
falls in only one or two storms.

Noble (1972) found no differences in spruce
germination on two soil types in a greenhouse
study in Colorado, but both soils were gravelly
sandy loams. On the other hand, striking differ-
ences were found in germination on two soil
types in western Montana (Roe et al. 1970).
Seeds were sown in the spring on a droughty
sandy loam and a black, moderately heavy loam
soil that retained a high moisture content
throughout the growing season. More than nine1
times as many seedlings germinated on the
heavier soil. Apparently, rapid surface drying
limited moisture for germination on the sandy
soil.

Germination of subalpine fir is usually good
on mineral soil seedbeds (Clark 1969, USDA-FS
1943). Fir is less exacting in its seedbed re-
quirements than spruce, and will germinate and
become established on a wider variety of seed-
beds (Alexander 1958b; Day 1963, 1964).

Factors Affecting Initial Survival
and Seedling Establishment

Most spruce seedling mortality occurs during
the first growing season, but losses can be sub-
stantial during the first 5 years after germina-
tion (Ronco 1967, 1970b; see also footnote 9).
The first growing season is considered here as
the period of initial survival, and the second
through the fifth growing seasons as the time of
seedling establishment.

INITIAL ROOT GROWTH

The rate of root growth is an important de-
terminant of initial survival of spruce seed-
lings. The further the root penetrates the soil,
the better chance the seedling has of surviving
drought, frost heaving, and erosion. Critical
rooting depth depends upon seedbed type,
weather, and soil properties.

First-year spruce seedlings (fig. 8), field
grown on mineral soil seedbeds under partial
shade on the Fraser Experimental Forest in Col-
orado, have a rooting depth of 3 to 4 inches, with
a total root length of 5 inches (Noble 1973b). In
an earlier study in the central Rocky Mountains,
the root length of vigorous 1-year-old spruce
seedlings averaged about 2.75 inches on seed-
beds where the depth of humus was about 1 inch

Figure 8. — Engelmann spruce seedling roots at the end of
the first growing season.

(Roeser 1924). In eastern Arizona, average
first-year spruce root penetration was 2.7
inches on shaded mineral soil (Jones 1971). In
the northern Rocky Mountains and British Co-
lumbia, first-year root penetration of spruce
seedlings under field conditions is only about
1.5 inches (Roe et al. 1970, Smith 1955).

No comparable data are available for subal-
pine fir in the central Rocky Mountains, but
first-year root penetration of its variety, cork-
bark fir, in Arizona averaged 3.4 inches (Jones
1971). In British Columbia, first-year root
length of subalpine fir averaged 2.7 inches (Eis
1965).

SEEDBED TYPE

In the undisturbed forest, spruce seedlings
become established on a variety of
seedbeds: duff, litter, partially decomposed
humus, decaying and moss-covered wood, and
on mounds of mineral soil upturned by
windthrown trees (Alexander 1958a, Dobbs
1972). These same seedbeds are available after
logging, with some additional mineral soil and
mineral soil mixed with humus. Removal of the
overstory, however, will produce new mic-
rohabitats, many of which will be unfavorable to
initial survival and seedling establishment.
Seedbed preparation is one way to modify limit-
ing environmental factors sufficiently to enable
seedlings to survive (Roe et al. 1970).

Spruce seedling survival and establishment '
after logging in the central Rocky Mountains 1
have generally been better on prepared mineral f
soil seedbeds than on other seedbed types '
(USDA-FS 1943, see also footnote 9), because I
mineral soil provides a more stable moisture 1
source than other seedbed types (Smith 1962). 5
Exceptions have been on south slopes, where "
shade has been more important to initial survi-
val than the seedbed type (see footnote 9). In P
some instances, subalpine fir has established 01
more readily on mineral soil, while in others i*
more fir seedlings were found on undisturbed P
seedbeds (Alexander 1966d, USDA-FS 1943). 41

In the Intermountain Region, Roe and JSP
Schmidt (1964) found that mechanically ex- la
posed mineral soil was superior to all other P
seedbeds for initial survival and establishment &
of spruce seedlings. Decayed wood, the natural luti
forest floor, and undisturbed duff were poor 111
seedbeds. In northern Idaho, spruce stocking sei
after 5 years was better on scarified seedbeds »i
where 40 percent or more of the area was ex- h
posed mineral soil than on the natural forest toi
floor or areas where scarification had exposed \ n
only about 20 percent of the surface in mineral k
soil (Boyd and Deitschman 1969). In southwest- j

ern Alberta on the Crowsnest Forest, spruce
seedling establishment was best on decayed
wood, but success was associated with moist
sites (Day 1963, Day and Duffy 1963).

Spruce seedling establishment on burned
seedbeds has been variable. Stocking was poor
or nonexistent in the central Rocky Mountain
and Intermountain Regions on burned piles and
windrows where burning left layers of loose ash
several inches deep, or generated such great
heat that rocks were fractured (Roe and
Schmidt 1964, USDA-FS 1943). Under these
conditions, burned seedbeds are not likely to
support any plants for long periods of time (Roe
et al. 1970). On the other hand, Boyd and
Deitschman (1969) found that spruce stocking
on seedbeds 5 years after prescribed burning
was as good as on scarified seedbeds where 40
percent or more of the area was exposed min-
eral soil.

The length of time seedbed treatment re-
mains effective also varies. On the Fraser Ex-
perimental Forest in Colorado, scarified seed-
beds on light-textured gravelly, sandy, loam
soils with a vaccinium ground cover were still
discernible 8 to 10 years after treatment,
whereas scarified seedbeds on more heavily
textured soils with a ground cover of grasses
and sedges were largely obliterated in 3 years
(Alexander 1969). Seedbeds on the latter soils
were not receptive long enough for seedlings to
become established. Mechanically scarified
and prescription-burned seedbeds did not last
longer than about 5 years in northern Idaho, but
that was sufficient time for seedlings to become
established (Boyd and Deitschman 1969). The
best results with natural or artificial seeding on
scarified seedbeds in the interior of British Col-
umbia were obtained in the first and second
growing seasons after seedbed treatment (Ar-
lidge 1967).

Spruce seedling survival and establishment
on natural seedbeds are limited by the depth of
organic matter, whether it is partially decom-
posed L, F, and H layers or an accumulation of
litter, duff, or other debris (Roe et al. 1970).
Although germination may have been good, few
spruces became established in the Intermoun-
tain Region where the depth of organic matter
on the seedbed exceeded 2 inches (Roe and
Schmidt 1964). Poor establishment was attrib-
uted to first-year root penetration that was too
shallow to keep pace with the rate at which the
seedbed dried out during the summer. Even
with a deeper first-year root penetration, seed-
lings in the central Rocky Mountains do not be-
come established readily on seedbeds covered
with heavy layers of duff, litter, or partially
decomposed humus (Roeser 1924).

CLIMATE

The climate of the Rocky Mountain subalpine
is characterized by extremes in insolation,
temperature, and moisture (Alexander 1958a,
1958b). Some of these extremes limit regenera-
tion success.

Insolation

Light intensity and total solar radiation are
high where spruce grows. Solar radiation in the
high mountains of Colorado can be as high as 2.2
cal/cm2/m on a clear day with scattered
cumulus clouds (Gates and Janke 1966, Spomer
1962). On cloudless days, daily and weekly mean
maximums of about 1.9 cal/cm2/m throughout
the summer have been reported (Spomer 1962).
Maximum air temperatures at 10,000 ft eleva-
tion rarely exceed 78° F, however (Roe et al.
1970).

Light is essential to seedling survival, but
spruce does not establish readily in the open at
high elevations in the Rocky Mountains. Seed-
lings develop a chlorotic appearance that is un-
related to nitrogen content (Ronco 1970c) and
subsequently die. High light intensity (visible
light can be as high as 13,000 footcandles (fc)
from shortly after sunrise to shortly before
sunset) is one of the factors contributing to the
mortality of seedlings planted in the open
(Ronco 1970d). Mortality can be reduced by
shading planted seedlings (Ronco 1961b, 1970a,
1972). Ronco (1970d) also found that photosyn-
thesis was higher for shaded than unshaded
seedlings. He suggests that solarization — a
phenomenon by which light intensity inhibits
photosynthesis — leads to irreversible tissue
damage and subsequent death of seedlings.

More natural seedlings were also established
in the Intermountain Region in the shade of non-
living material than elsewhere (Roe and
Schmidt 1964). Shade not only reduced light in-
tensity, but lowered temperatures and con-
served moisture, thereby improving the mic-
roenvironment for seedling survival and estab-
lishment.

On the other hand spruce seedlings cannot
compete with subalpine fir in the low light in-
tensities commonly found in dense natural
stands.

Temperature

Engelmann spruce is restricted to high eleva-
tions because of low tolerance to high air temp-
eratures (Bates 1923, Hellmers et al. 1970).

However, solar radiation at high elevations
heats exposed soil surfaces and increases water
losses from both seedlings and soil by both
transpiration and evaporation. Drought or heat
girdling may cause mortality, especially among
first-year seedlings (Roe et al. 1970).

Tree seedlings in the succulent stage are par-
ticularly susceptible to stem girdling. The cor-
tex is killed by a temperature of 130° F, but pro-
longed exposures to lower temperatures may
also be lethal. On the Fraser Experimental
Forest, soil surface temperatures have ex-
ceeded 150° F in the open on both north and
south slopes at 10,500 ft elevation in the month
of June (see footnote 9). Maximum air tempera-
ture during this period did not exceed 78° F. In
western Montana, at lower elevations, soil sur-
face temperatures exceeded 160° F on gentle
north slopes several times during one summer
(Roe et al. 1970). Early shade protection im-
proved survival of newly germinated spruce
seedlings; 30 to 50 percent of the seedlings were
lost to heat girdling on unshaded plots, com-
pared to 10 percent on shaded plots. Day (1963)
studied heat and drought mortality of newly
germinated spruce seedlings in southwestern
Alberta, and found that when water was ex-
cluded nearly three-fourths of the mortality on
four different unshaded seedbed types was
caused by heat girdling. Surface temperatures
as low as 113° F caused heat girdling, but losses
were not high until soil surface temperatures
were above 122° F. Shading reduced heat gird-
ling on all seedbed types. Soil surface tempera-
tures in excess of lethal levels for spruce seed-
lings, especially on burned seedbeds, have been
reported in British Columbia (Smith 1955).

The growing season is short at 10,000 ft eleva-
tion in the Rocky Mountains, and frost can occur
any month of the growing season (Alexander
1958a, Ronco 1967). Frost is most likely to occur
in depressions and cleared openings because of
cold air drainage and radiation cooling. Newly
germinated spruce seedlings are susceptible to
damage from early fall frosts. In a greenhouse
and laboratory study, new seedlings did not
survive temperatures as low as 15° F until about
10 weeks old (Noble 1973a). Terminal bud for-
mation began at 8 weeks; buds were set and
needles were mature at 10 to 12 weeks after
germination.

After the first year, seedlings are most sus-
ceptible to frost early in the growing season
when tissues are succulent. Shoots are killed or
injured by mechanical damage resulting when
tissue freezes and thaws. Frost damage has
been recorded in most years in Colorado (Ronco
1967). In light frost years damage was minor,
but heavy frosts either damaged or killed all
new shoots of open-grown seedlings (fig. 9).

Figure 9. — Frost damage to an open-grown, planted En-
gelmann spruce seedling.

Furthermore, the loss of new shoots was at the
expense of stored food reserves. Frost damage
was nearly eliminated by shading the seedlings
(Ronco 1967).

In the early fall, the combination of warm
daytime temperatures, nighttime temperatures
below freezing, and saturated soil unprotected
by snow are conducive to frost heaving. On the
Fraser Experimental Forest, these conditions
have occurred in 2 out of the past 5 years (see
footnote 9). Frost heaving has been one of the
principal causes of first-year seedling mortality
on scarified seedbeds on north slopes. Further-
more, seedlings continue to frost heave after
four growing seasons. Shading has reduced
losses by reducing radiation cooling.

Moisture

The moisture condition of the seedbed during
the growing season largely determines first-
year seedling survival. On some sites in the cen-
tral Rocky Mountains, summer drought is re-
sponsible for substantial first-year mortality, ,
especially in years when precipitation is low or ;:
irregular. On the Fraser Experimental Forest,
drought and desiccation have caused more than
half of the first-year seedling mortality in 4
years of observation on south slopes (see foot-
note 9). On north slopes during the same period,
drought has accounted for only about one-third
of first-year seedling mortality. On the other
hand, frequent watering during dry summers
did not increase first-year survival of planted
spruce in central Colorado (Ronco 1967).

In the northern Rocky Mountains, late spring
and early summer drought is a serious threat

most years to first-year seedlings. In western
Montana, all seedlings on one area were killed
by drought in a 2-week period in late summer
when their rate of root penetration could not
keep pace with soil drying during a prolonged
dry period (Roe et al. 1970). Late spring and
early summer drought is also a serious cause of
seedling mortality in the Southern Rockies.

The moisture provided by precipitation dur-
ing the growing season is particularly critical to
the survival of seedlings during the first year.
Alexander and Noble (1971) studied the effects
of amount and distribution of watering treat-
ments on seedling survival in the greenhouse.
Treatments simulated common summer pre-
cipitation patterns in north central Colorado.
They concluded that, under favorable seedbed
and environmental conditions: (1) At least 1
inch of well-distributed precipitation is needed
monthly before seedlings will survive drought;
(2) with this precipitation pattern, more than 1.5
inches of monthly rainfall is not likely to in-
crease seedling survival; but (3) few seedlings
will survive drought with less than 2 inches of
rainfall monthly when precipitation comes in
only one or two storms.

Summer precipitation may not always benefit
seedling survival and establishment. Summer
storms in the Rocky Mountains may be so in-
tense that much of the moisture runs off, espe-
cially from bare soil surfaces. Moreover, soil
movement on unprotected seedbeds buries
some seedlings and uncovers the roots of others
(Roe et al. 1970).

SOIL

Throughout the Rocky Mountains, spruce and
fir grow on a wide range of soils — described by
Johnson and Cline (1965) and Retzer
(1962) — but there is little information about
the soil requirements for regeneration. Noble
(1972) compared first-year spruce seedling
survival and growth on two soils in the
greenhouse. One soil — Bobtail gravelly sandy
loam — is a Sols Bruns Acides which developed
in place under a mixed spruce-fir-lodgepole
pine stand from mixed schists and gneisses that
were metamorphosed from granitic rock. The
other soil — Darling gravelly sandy loam — is a
Podzol developed in place under a spruce-fir
stand from coarse-textured materials weath-
ered from mixed schists and gneisses. The Bob-
tail soil crusted and compacted when
watered — as it did in the field — and root
penetration was significantly less than on Dar-
ling soils. Consequently, 1.5 inches of water
well-distributed monthly was required to obtain
survival on Bobtail soils, whereas significant

survival was obtained on Darling soils with 1
inch of water well distributed monthly. Top
growth and total dry matter production after 24
weeks were about the same on both soils. Alex-
ander (1958a) reported that spruce generally
establishes and makes good growth on moder-
ately well-drained silt and clay loam soils de-
veloped in place from volcanic and fine
sedimentary rock, and on alluvial soils de-
veloped from a variety of parent materials, be-
cause these soils do not dry out rapidly. Spruce
does not establish or grow as well on shallow,
dry, coarse-textured sands, gravels, heavy clay
surface soils, or saturated soils.

No information is available on the range of pH
tolerated by spruce and fir, or their nutrient
requirements.

High-intensity storms and runoff from
snowmelt cause erosion that results in seedling
mortality on mineral soil seedbeds (Roe et al.
1970). In the central Rocky Mountain and In-
termountain Regions, seedlings are destroyed
by either scouring that uncovers the roots or
deposition that buries the seedlings (Roe and
Schmidt 1964, see also footnote 9).

DISEASES

Newly germinated seedlings are killed by
damping-off fungi (Ronco 1967, see also foot-
note 9). Losses normally occur early in the
growing season before seedlings cast their
seedcoats, and can be serious on all seedbed
types if they remain damp for long periods of
time. Damping-off was responsible for 17 per-
cent of the first-year seedling mortality in cen-
tral Colorado on both mulched and unmulched
mineral soil seedbeds in a year when the grow-
ing season was particularly wet (Ronco 1967).
Damping-off was the principal cause of mortal-
ity of newly germinated seedlings in the
greenhouse when they were watered suffi-
ciently to keep the soil surfaces from drying
(Alexander and Noble 1971, Noble 1972).

Snowmold fungus (Herpotrichia nigra
Hartig) occasionally damages or kills both
natural and planted seedlings (Ronco 1967,
1970a; see also footnote 9). Losses are most se-
vere when seedlings remain under the snow too
long, as in years of heavy snowfall or when
weather retards snowmelt in the spring, or in
depressions where snow normally accumulates
and melts slowly.

ANIMAL DAMAGE

A number of animals damage and kill young
seedlings. Haig et al. (1941), Roe et al. (1970),

Figure 10. — Clipping damage to newly germinated spruce seedlings by juncos. Fraser
Experimental Forest, Colorado.

and Ronco (1967) have suggested that mice con-
sume cotyledonous seedlings as well as unger-
minated seeds. Those workers based their con-
clusions on observations of seedlings that were
clipped shortly after germination while seed-
coats were still attached, but there is no
documented evidence of mice actually doing the
damage. A study by Noble and Shepperd (1973)
indicates that the grey-headed junco (Junco
caniceps Woodhouse) is probably responsible
for clipping mortality and damage in the central
Rocky Mountains previously attributed to mice
(fig. 10). Established seedlings are not immune,
however, to rodent damage. During some win-
ters, established seedlings are debarked and
killed by mountain voles, and mountain pocket
gophers (Thomomys talpoides (Richardson))
periodically cause heavy mortality to spruce
plantations up to 3 to 4 years after planting
(Ronco 1967, 1970a).

The extremely small size of young spruce
seedlings makes them especially vulnerable to
damage by grazing and browsing animals. In
western Montana, cattle — in one trip through a
seedling survival study area — trampled or
killed 10 percent of the marked first-year
spruce seedlings. They were either buried or
kicked out of the ground (Roe et al. 1970). Tram-
pling damage by cattle and big-game animals is
likely to be more severe on prepared seedbeds,
especially if they have been plowed or disked,
because the ground provides easy travel routes.
Spruce is seldom eaten by these animals, but

young subalpine fir is frequently browsed heav-
ily by big-game.

GROUND VEGETATION

Understory vegetation can be either a benefit
or a serious constraint to spruce seedling survi-
val and establishment (Alexander 1966d, Day
1964, Ronco 1972). Observations of natural and
artificial regeneration on several areas in the
central Rocky Mountains have indicated spruce
seedlings become established more readily on
sites protected by such plants as willow (Salix
spp.), shrubby cinquefoil (Potentilla fruticosa
(L.) Rydb.), fireweed (Epilobium angustifolium
L.), and dwarf whortleberry (Vaccinium spp.)
than in the open. These plants shade seedlings
without seriously depleting soil moisture. In
contrast, mortality has been recorded when
seedlings started near clumps or scattered in-
dividual plants of grasses or sedges, or her-
baceous plants such as bluebells (Mertensia
spp.) which spread to form a dense, solid cover
with roots completely occupying the soil. Death
is due to root competition for moisture and
smothering by cured vegetation compacted
under dense snow (Ronco 1972). The probability
of regeneration success on an area with a com-
plete cover of dense sod of grasses and sedges is
low. In Utah, Pfister (1972) rated the environ-
ment for spruce regeneration success as severe
in habitat types where the understory was

dominated by Ribes montigenum, and moderate
where the understory was dominated by
Berberis repens. He concluded that natural re-
generation success could be obtained in these
habitat types only by maintaining a continuous
forest cover.

SITE QUALITY

The evaluation of site quality is essential to
the land manager as a means of identifying and
intensifying management practices where
timber production has the greatest potential.

Conventional Determination

In addition to being dominants, trees selected
for measurement should meet the following
criteria:

1. Even-aged — not more than a 20-year spread
in the age of the dominant stand.

2. At least 20 years old at breast height
— preferably 50 years old or older, because
of the variability in height growth of trees on
the same site at ages 20 to 50 years.

3. Show no visible evidence of crown damage,
such as broken or forked tops, disease, or
excessive sweep or crook.

4. Increment core shows a normal pattern of
ring widths from pith to cambium, indicating
no evidence of past injuries nor prolonged
suppression.

Site index is the only method now available
for estimating the potential productivity of
spruce-fir forests in the central and southern
Rocky Mountains. Alexander (1967a) prepared
curves of the height and age relationship of
dominant spruces that are suitable for estimat-
ing site index at base age 100 years in spruce-fir
stands where age at breast height is at least 20
years (fig. 11). Data for these curves came from
2,100 dominant spruces with annual ring se-
quences showing no evidence of past suppres-
sion, on 350 plots in southern Wyoming and
throughout Colorado. These plots were selected
to represent the available range in density,
site quality, and age.

Height measurements to the nearest foot and
age at breast height from increment borings of
at least six dominant spruce trees should be
averaged when the site index curves are used.
This will provide an integrated site index value
that applies over the area occupied by trees
aged and measured. Little improvement in
sampling error is gained by measuring more
than six trees (Brickell 1966).

100 140 180 220
Breast height age (years)

Figure 11. — Site index curves for Engelmann spruce in the
central Rocky Mountains. Base age: 100 years, breast
height.

Determination From Soil and Topography

The conventional method of height-age can-
not be used to estimate site index if there are no
trees present, or if trees are either too young or
unsuitable for measurement. For example, the
height-age curves developed by Hornibrook
(1942) are not suitable for estimating site index
because they were based on residual trees left
after partial cutting, many of which were not
dominants or codominants in the original stand.

Site index for granitic soils in northern Col-
orado and southern Wyoming can be estimated
from the depth of soil to the top of the C horizon
and elevation in feet (Sprackling 1972). Data
came from 127 plots located on the Roosevelt,
Arapaho, Medicine Bow, and Routt National
Forests. The equation from which figure 12 is
derived is shown below:

Y* = -106.64 + 62.46Xt + 809.40X,
where

Y = site index

X j = log of soil depth to top of C

horizon, in inches
X, = 1000/elevation, in ft.

S y-x

9.00; ± R2 = 0.65

Site indexes estimated from these soil and
topographic factors are strictly applicable only
to the point sampled. The more variable the site,
the more points must be sampled to precisely
estimate site index over the area. In practice,
however, site index sampled from what appear
to be extremes on the ground for any given area
is usually all that is needed.

Soil-topographic site indexes have not been
developed for other areas in the central and
southern Rocky mountains.

Elevation (feet)

Soil depth (inches)

Figure 12. — Site index for Engelmann spruce on granitic
soils in southern Wyoming and northern Colorado, from
soil depth to the top of the C horizon and elevation
(Sprackling 1972).

If we are to develop a true measure of site
quality that includes potential productivity, re-
generation capacity, and successional trends,
the concept of "total site" that includes vegeta-
tion, soils, and landform appears to offer the
best possibility of success.

GROWTH AND YIELD

Forest management in the spruce-fir type in
the central Rocky Mountains is in a period of
transition to more intensive management. Pre-
diction of future yields and knowledge of indi-
vidual tree growth are essential to the develop-
ment of management practices for a variety of
uses.

Growth of Individual Trees

Diameter growth is usually used to measure
release because of its sensitivity to changes in
stand density. Observations of diameter growth
of residual spruce and fir left after partial or
diameter-limit cutting show that individual
trees respond to release, and the degree of re-
lease is related to initial diameter, tree vigor,
and number of competitors (Hornibrook 1942,

Roe and DeJarnette 1965, Stettler 1958). How-
ever, conventional thinning studies have not
been made in spruce-fir forests in the central
Rocky Mountains, partly because of the rela-
tively few young stands and partly because
spruce and fir do not grow in such dense stands
as are common in lodge pole pine. A yield study1 1
currently in progress in the central and south-
ern Rocky Mountains will provide some of the
data needed to determine the diameter growth
of spruce and fir in relation to stand density,
age, and site quality.

The height growth of individual trees is
primarily important because of the relationship
between site quality and height of dominant
trees at index age. For tolerant species such as
spruce and fir, height growth of dominant trees
is unaffected over a wide range of stand den-
sity; consequently volume growth is also less
affected by changes in stand density for any
given site index and age. Dominant height is,
therefore, a valid site index upon which to base
yield prediction. The changes in the dominant
height of spruce with age and site quality are
shown in figure 11. At age 120 years, for exam-
ple, dominant height varies from 46 to 130 ft in
response to variations in site quality. Age at
breast height is used as index age because the
slow, variable height growth to 4.5 ft makes the
use of total age meaningless.

Under stand conditions, the crowns of spruce
tend to be parabolic in shape, while fir is more
conical. The relationship of crown size to indi-
vidual tree growth has been determined for
spruce in the central Rocky Mountains (Alex-
ander 1971). Figure 13 shows the relationship of
the crown width of open-grown spruces to
diameter at breast height.

New volume tables and point sampling fac-
tors have been prepared for Engelmann spruce
in Colorado and Wyoming (Myers and Edmins-
ter 1972). The nineteen tables include: (1) gross
volumes in total and merchantable cubic feet,
(2) gross volumes in board feet, both Scribner
and International 1/4 log scales, and (3) point
sampling factors for merchantable cubic feet
and board feet.

Volume on an area may be determined from
either: (1) measurements of tree diameters and
heights, (2) measurements of diameters and
sufficient heights to convert the tables to local
volume tables, or (3) tree counts obtained by
point sampling (Myers and Edminster 1972).

"Unpublished data on file with study FS-RM-1201.25,
Rocky Mt. For. and Range Exp. Stn., Fort Collins, Colo.

38 r

2 -

I 1 1 1 I I i i i i i I i I I 1—

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Diameter at breast height (inches)

Figure 13. — Relationship of crown width to stem diameter
at breast height for open-grown Engelmann spruce.

Yields Per Acre

NATURAL STANDS

With the high proportion of spruce-fir still in
old-growth stands, the forest manager must
largely accept what nature has provided during
the period of conversion to managed stands.
Growth estimates based on Forest Survey in-
ventories, rather than detailed growth and yield
studies, indicate that average annual growth
over all sites in old-growth spruce-fir forests is
only about 80 to 100 fbm per acre. Average vol-
umes per acre vary from 5,000 to 15,000 fbm on
poor sites to 25,000 to 40,000 fbm on better sites.
Volumes as high as 80,000 to 100,000 fbm per
acre have been reported (Pearson 1931, Thomp-
son 1929, USDA-FS 1942).

MANAGED STANDS

Large areas of old-growth spruce-fir are
being converted into stands that must be man-
aged from the regeneration period to final har-
vest. The term managed as used here refers to
control of stand density throughout the life of
the stand. Yield tables for managed stands are

essential to the land manager as a basis for deci-
sions on:

1. Site quality classes that will repay the cost of
thinning and other cultural treatments.

2. Levels of growing stock — including the
frequency of thinning or intermediate
cutting — to meet management objectives.

3. Length of rotation, cutting cycles, and allow-
able cut for different cutting methods, man-
agement goals, and utilization standards.

4. The place of timber management in
mulitple-use management. Better decisions
are possible regarding key uses when the
timber potential of managed stands can be
forecast.

Furthermore, yield tables that show what can
be accomplished by different management
practices will provide goals toward which con-
version to managed stands can be directed.

The only growth-prediction tool now available
for spruce-fir stands in the central Rocky
Mountains was developed 30 years ago by Hor-
nibrook (1942). However, it is for selectively cut
stands, for sawtimber only, and for stand struc-
tures that are no longer management goals.

Most growth-prediction tools developed in the
past have been either (1) normal yield tables, (2)
empirical yield tables, or (3) experience or
variable-density yield tables. Each method has
deficiencies and limitations that make it unsuit-
able for developing growth prediction tools
necessary to meet present and future needs in
spruce-fir forests.

A method of yield table preparation for man-
aged stands that avoids the limitations inherent
in other methods has been developed by Myers
(1971). It has been used to predict yields for
managed stands of Black Hills ponderosa pine
(Pinus ponderosa Laws.) and lodgepole pine
(Myers 1966, 1967). Data are now being col-
lected in the central Rocky Mountains and
analyzed by Myers (1971) field and computer
simulation procedures to develop yield tables
for managed spruce-fir stands. The simulation
program will generate tables derived from field
data on past growth in relation to stand density,
age, and site quality obtained from a large
number of temporary plots in existing unman-
aged but uniformly spaced spruce-fir stands..
The program can produce a series of yield ta-
bles which show how projected outcomes will
vary in response to changes in cultural treat-
ments and/or variations in original stand and
site conditions. With this series of yield projec-
tions, the manager can examine the probable
results of his operations, make necessary
changes in the management of his resources,
and study the effects of these changes before
money is spent on them (Myers 1971).

SILVICULTURE AND MANAGEMENT OF
OLD GROWTH

Regeneration Silviculture

Spruce-fir forests can be harvested by clear-
cutting and shelterwood, and selection cutting,
plus their modifications. The objective of each
regeneration system is to harvest the timber
crop and obtain adequate reproduction. The
choice of cutting method depends on manage-
ment objectives and environmental considera-
tions, but stand conditions, associated vegeta-
tion, and windfall and spruce beetle susceptibil-
ity that vary from place to place on any area,
impose limitations on how individual stands can
be handled. Cutting to bring old-growth under
management is likely to be a compromise,
therefore, between what is desirable and what is
possible. Management on many areas may in-
volve a combination of several partial cutting
treatments, clearcutting, and sanitation salvage
cutting.

CLEARCUT AREAS

Clearcutting is a regeneration system that
harvests the timber crop in one step. Since a
large proportion of the spruce-fir type is in
overmature sawtimber stands that offer little
opportunity for future management because of
their advanced age, relatively slow growth, and
susceptibility to wind and insects, forest mana-
gers concerned with timber production have
most often elected to convert old-growth to
managed stands by clearcutting in strips,
patches, and blocks. Harvesting and regenera-
tion practices developed in the central Rocky
Mountains have therefore been directed toward
this objective. Much of the criticism recently
leveled at clearcutting in spruce-fir has a valid
basis, particularly where large openings were
cut, geometric patterns were used that did not
complement the landscape, unsightly logging
debris was left on the ground, and areas did not
regenerate. The cause of these criticisms can be
eliminated if available knowledge is put into
practice. From a silvicultural point of view,
therefore, clearcutting is still an acceptable
harvesting method in spruce-fir forests. In fact,
under some conditions it is the only alternative
to no cutting. Furthermore, a combination of
cleared openings and high forests meets the
needs of such key uses as water production and
wildlife management. Consequently the
following — taken chiefly from Roe et al.
(1970) — will be directed at the practices
needed to regenerate clearcuts. To restock
these cutovers, the manager should first con-

sider the cultivation of existing acceptable
advanced reproduction before planning on sub-
sequent restocking by natural or artificial
means.

Management with Advanced Reproduction

Although many spruce-fir forests have an un-
derstory of advanced growth, wide variations in
age, composition, quality, and quantity of ad-
vanced reproduction require careful evaluation
of the potential for future management. This
management potential must be determined be-
fore cutting. One course of action is followed if
the advanced reproduction is to be managed,
another if a manageable stand is not present,
cannot be saved, or the manager chooses to de-
stroy it and start over (Roe et al. 1970).

Prelogging Evaluation. — The initial exami-
nation must answer the following questions: (1)
How much of the area is stocked with accepta-
ble seedlings and saplings, and will that stock-
ing insure a satisfactory replacement stand? (2)
Can it be logged economically by methods that
will save advanced reproduction? Is the timber
volume too heavy to save advanced reproduc-
tion if it is removed in one cut? (3) How much of
the area will require subsequent natural or arti-
ficial regeneration, either because advanced
reproduction is not present or will be destroyed
in logging?

Since any kind of cutting is likely to destroy at
least half of the advanced growth, a manageable
stand of advanced reproduction before cutting
should contain at least 600 acceptable seedlings
and saplings per acre of either spruce or fir.
There are few data available on the growth re-
sponse of advanced reproduction; the following
criteria are therefore based largely on experi-
ence and observation. To be acceptable, repro-
duction must be of good form, able to make vig-
orous growth when released, and be free of de-
fect or mechanical injury that cannot be out-
grown. Trees over 4 inches d.b.h. may be ac-
ceptable, but they should not be included in the
prelogging regeneration survey because they
are more likely to be damaged or destroyed in
logging or windthrown after logging. Stands or
portions of stands not meeting these criteria
will have to be restocked with subsequent
natural or artificial regeneration (Roe et al.
1970).

Cutting and Slash Treatment to Save Ad-
vanced Regeneration. — Mature and overma-
ture trees should be cut to release advanced
reproduction and harvest merchantable vol-
ume. Seed sources need not be reserved from

cutting unless required for fill-in stocking. If it
is necessary to reserve trees for esthetic pur-
poses or maintain high forests for other uses,
some form of partial cutting that will release
and protect advanced growth should be con-
sidered. The size, shape, and arrangement of
openings cut is not critical from a regeneration
standpoint, but to be compatible with other key
uses, openings should be no wider than about
five to eight times tree height, irregular in
shape, and blend into the landscape. Not more
than one-third of any drainage or Working Cir-
cle should be cut over at any one time.

Protection of advanced reproduction begins
with a well-designed logging plan (Roe et al.
1970). Logging equipment must be suited to the
terrain. Skidding, movement of equipment, and
other activity must be rigidly controlled. To
minimize damage to advanced reproduction and
disturbance to soil, skid roads must be located
and marked on the ground before cutting. They
should be at least 200 ft apart. Movement of
skidding equipment must be confined to these
skid roads to eliminate indiscriminate travel
over the area. Trees should be felled into open-
ings where possible at a herringbone angle to
the skid road so as to reduce disturbance when
logs are moved onto the skid road (Alexander
1957a, Roe et al. 1970). It may be necessary to
deviate from a herringbone felling angle in
order to drop the trees into openings. If this is
the case, the logs will have to be bucked into
short lengths to reduce skidding damage.

Furthermore, there must be close coordination
between the felling and skidding operations,
because it may be necessary to fell and skid one
tree before another is felled. Dead sound mater-
ial and snags that are felled should be skidded
out of the area to minimize the amount of slash
and unmerchantable material to be disposed of
after logging.

Slash treatment should then be confined to
areas of heavy concentrations as required for
protection from fire and insects or preservation
of esthetic values (Roe et al. 1970). Slash must
be treated carefully to avoid unnecessary dam-
age to advanced reproduction — care taken in
logging is wasted if advanced reproduction is
destroyed in slash disposal. If trees are felled
into openings as much as possible, a minimum of
turning and travel with brush dozers will be
needed to concentrate the slash for burning.
Sufficient piles should be made so that burning
is confined to the smallest area possible.

Postlogging Reevaluation. — Regardless of
how much care is taken in logging and slash
treatment, a certain amount of advanced repro-
duction will be damaged or destroyed. The area
must be surveyed to: (1) Determine the extent
of damage to the reproduction. At least 300 ac-
ceptable seedlings and saplings per acre must
have survived to consider the area adequately
stocked plus whatever trees larger than 4
inches d.b.h. survive intact (fig. 14). Areas that
do not meet these standards will need fill-in

Figure 14.— Adequate stocking of advanced spruce and fir reproduction after clearcutting and
slash disposal. Fraser Experimental Forest, Colorado.

or supplemental stocking. (2) Plan stand
improvement — cleaning, weeding, and
thinning — to release crop trees. Guidelines are
available to aid in marking trees to be cut or left
(Alexander 1957b).

Cutover areas should not be considered in an
adequate growing condition until the crop trees
are free to grow and the necessary fill-in plant-
ing or natural regeneration is complete (Roe et
al. 1970).

Management for Reproduction After Cutting

If advanced reproduction is not adequate, the
area must be regenerated by natural or artifi-
cial means after logging.

Cutting unit layout, logging plans, slash dis-
posal, and seedbed treatment should be de-
signed to (1) facilitate seed dispersal, (2) pro-
mote seedling survival and establishment, and
(3) create favorable growing conditions. If natu-
ral regeneration fails, plans must then be made
to use artificial regeneration (Roe et al. 1970).

Clearcutting can be by patches, blocks, or
strips. Such cutting can be readily adapted to
multiple use land management by judicious
selection of size, shape, and arrangement of
openings in combination with other high-forest
cutting practices.

Size of Cutting Unit. — Requirements for
seed dispersal and site preparation will influ-
ence the size of opening that will restock to
natural regeneration. The best seedbed prep-
aration is wasted if the seedbed does not receive
sufficient seed; likewise, any quantity of seed is
wasted if it does not fall on a receptive seedbed
(Roe et al. 1970). The cutting unit must there-
fore be designed so that seed from the surround-
ing timber margin reaches all parts of the open-
ing unless supplementary artificial regenera-
tion is planned. Effective seeding distance and
aspect determine the size of opening.

The tabulations below are guides developed
for the central Rocky Mountains. They are
based on 12 years of seed production and dis-
persal data from six areas in Colorado (Alexan-
der 1969, Ronco 1970b, Ronco and Noble 1971)
and 5 years of spruce survival data from the
Fraser Experimental Forest in Colorado in a
Picea engelmannii-Vaccinium spp. habitat type
(see footnote 9). Effective seeding distance as
used here is defined as the distance to which
sufficient sound seed is dispersed to provide an
arbitrary minimum of 1,000 first-year seedlings
on (1) mineral soil seedbeds where competition
from competing vegetation has been elimi-
nated, and 50 percent overhead shade and pro-
tection from rodents provided; and (2) natural

seedbeds with only protection from rodents
provided. The number of first-year seedlings
expected to become established on two aspects

is:

Seedbed Seedlings
and per 1,000

aspect sound seeds

Shaded, mineral soil:

North 50

South 10

Unshaded, natural:

North 5

South 0

The estimated maximum distance that can be
seeded from all sides and size of opening that
can be made on two aspects based on moderate
to good seed production is:

Maximum —

Seedbed Distance Size

and that can opening

aspect be seeded (tree

(ft) heights)

Shaded, mineral soil:

North 450-500 5-6

South 150-200 2-2 V2

Unshaded, natural:

North 50-100 I-IV2

South 0 0

Based on these seeding distances, the follow-
ing conclusions can be drawn:

1. Clearcutting for natural regeneration is
most likely to succeed on north and east as-
pects, if the right combination of mineral soil
and shade has been created. Even then, more
than one good seed year will likely be re-
quired to obtain adequate restocking.

2. Clearcutting on south and west aspects is not
likely to result in an acceptable stand of new
reproduction in a reasonable period of time,
even with favorable seedbed and environ-
mental conditions, without fill-in planting to
bring reproduction to the minimum accepta-
ble standard.

3. Where larger openings than shown are cut on
north and east slopes, it will be necessary to
plant the area beyond effective seeding dis-
tance.

4. Where the seed source is of poor quality, plan
to plant the cutovers.

Similar guides developed for Intermountain
Region conditions by Roe et al. (1970) show that
larger openings than indicated here can be re-
stocked if the seed source contains 200 or more
ft2 of basal area in spruce trees 10 inches d.b.h.
and larger.

Windfall. — A significant consideration in the
location of cutting unit boundaries is windfirm-
ness. Not only are the trees along the margins of
openings the source of seed for regeneration,
but they also provide ideal breeding grounds for
spruce beetles when windthrown. The following
guidelines for minimizing windfall around the
perimeter of clearcut openings were developed
in Colorado (Alexander 1964, 1967b):

1. Protection from wind for the vulnerable
leeward boundaries is most important.

2. Do not locate cutting boundaries where
they will be exposed to accelerated winds
funneling through saddles in ridges to the
south and west of the cutover area, espe-
cially if the ridges are at high elevations.
Success in reducing blowdown from that
kind of exposure depends upon the ability of
the forester who lays out the cutting-unit
boundaries to recognize exceptionally
hazardous situations.

3. Avoid locating cutting boundaries on ridges
or near saddles in ridges, especially
ridgetops of secondary drainages to the lee
and at right angles to the main drainage
when the latter is a narrowing valley with
steep slopes. One cutting unit should strad-
dle each ridgetop and extend downslope in
both directions for a distance of at least 200
ft. That unit may be cut or uncut. Such an
arrangement will avoid leaving a cutting
boundary on the top of a ridge.

4. Lay out each unit so the maximum amount
of cutting boundary is parallel to the con-
tour or along a road where topography,
soils, and stand conditions will permit.

5. Do not lay out cutting units with dangerous
windcatching indentations or long, straight
lines and square corners in the leeward
boundary or in boundaries that are parallel
to stormwinds. V- or U-shaped indentations
in the boundary can funnel wind into the
reserve stand. Long, straight cutting-
boundary lines and square corners also de-
flect the wind and cause increased vel-
ocities where the deflected currents con-
verge with others such as a windstream
flowing over a crest. Irregular cutting
boundaries without sharp indentations or
square corners lessen the opportunity for
deflection and funneling of air currents.

6. Do not locate cutting boundaries on poorly

drained or shallow soils. Trees grown under
these conditions are shallow rooted and
susceptible to windthrow.

7. Locate cutting boundaries in stands of
sound trees. Trees with decayed roots and
boles or root systems that were cut or torn
during road building or log skidding opera-
tions are poor windfall risks.

8. Locate cutting boundaries in immature
stands when possible. Stands of young trees
are usually less easily uprooted by strong
winds.

9. Locate cutting boundaries in poorly stocked
stands. Open-grown trees are more wind-
firm than trees grown in dense stands.

10. Avoid locating cutting boundaries in areas
where there is evidence of old prelogging
blowdowns.

11. Reduce blowdown in areas with exception-
ally hazardous windfall potential by locat-
ing the vulnerable leeward boundaries
where hazards are below average, or by
eliminating those boundaries by progres-
sive cutting into the wind.

Seedbed Preparation and Slash Treat-
ment.— There are a number of things to
consider when planning the treatment of spruce
slash: (1) slash 8 inches in diameter or larger
provides a habitat for spruce beetles; (2) it pro-
vides beneficial shade for germination and
seedling establishment; (3) in heavy concentra-
tions, it obstructs natural seedling establish-
ment; and (4) it creates an adverse visual im-
pact.

Burning slash in large concentrations such as
windrows or piles often creates enough heat in
the soil to inhibit the development of any kind of
plant growth for an unknown period of time.
Windrows or piles should therefore be small or
narrow, and should cover a minimum propor-
tion of the area.

Mineral soil can be exposed by mechanically
scarifying the ground surface, sometimes in
connection with slash disposal or by broadcast
burning. To be effective, broadcast burning
should accomplish certain objectives. It should
consume most but not necessarily all of the duff
or organic material on the ground, and it should
burn hot enough to destroy some or all or the
competing vegetation. On the other hand, it
should not burn so hot that a deep layer of loose
ashes accumulates, the mineral soil changes
color, or the rocks fracture. It must leave cull
logs, tops, and other large slash to provide shade
and protection for soil and seedlings (Roe et al.
1970). Timing of the burn is exceedingly impor-
tant. The spruce type is generally so cool and
moist that times when effective broadcast
burns can be achieved are limited. The key to

the time to burn is the moisture content of the
duff — it must be dry enough to be consumed. If
only the surface is dry, a blackened organic
layer that inhibits seedling establishment will
remain (Roe et al. 1970).

Careful mechanical scarification will prepare
a satisfactory seedbed if it exposes mineral soil
and destroys some of the competing vegetation,
but leaves shade protection. At least 40 percent
of the area should be left as exposed mineral
soil. It may be necessary, however, to rearrange
some of the residual slash to provide adequate
shade. Tractors equipped with brush blades
should be used. A complete cleanup job is
neither necessary nor desirable. There is a dou-
ble advantage in not cleaning up too thoroughly:
First, residual tops and slash shade the seedbed;
second, residual organic material reduces soil
erosion. Cut green spruce material over 8
inches in diameter should be removed or treat-
ed to prevent the buildup of spruce beetle pop-
ulations, but true fir material may be left. On
highly erodible soils, the duff layer should be
removed along the contour, preferably in strips
the width of the dozer blade, with untouched
strips intervening. Some of the larger debris
may then be pushed back on the scarified strips
for protection from erosion, and the dozer
walked over it at right angles to the strips to
break it down (Roe et al. 1970).

Management for Artificial Regeneration

Planting. — Guidelines for planting spruce in
the central and southern Rocky Mountains have
been prepared by Ronco (1972). His recommen-
dations are summarized here unless otherwise
indicated.

1. Need and Timing. — Good sites should be
planted immediately after logging where
there is not a manageable stand of advanced
reproduction, and where local experience
has shown that natural regeneration is likely
to take a long time. Areas logged and pre-
pared for natural regeneration that fail to
restock in 3 to 5 years should be planted be-
fore invasion by other vegetation has com-
pletely occupied the site. Experience has
shown that a minimum goal should be about
300 well-established spruce seedlings in ad-
dition to whatever other species may have
become established (Roe et al. 1970).

Planting cutover areas has several advan-
tages. By growing stock in nurseries, many
of the vagaries of the natural regeneration
system are avoided, such as unpredictable
seed years, irregular seed dissemination,
and high rates of early seedling mortality.
Planting permits better control of stand den-

sity, tree distribution, and species and
genetic composition of the stand. Planting,
unlike natural regeneration, does not impose
a restriction on size of cutting units, and it
removes the necessity of reserving mer-
chantable trees for seed. Furthermore, suc-
cessful planting may shorten the regenera-
tion period (Roe et al. 1970).

There are, however, some disadvantages
in planting. Field planting requires close
coordination between cutting plans and the
availability of planting stock. Delay in plant-
ing after logging may increase the costs of
site preparation. Costs of surviving seed-
lings are frequently higher than those of
natural regeneration. Close supervison is
needed to assure planting of only large, vig-
orous stock, proper storage and transporta-
tion, proper handling of stock from the nur-
sery until planted, and proper planting tech-
niques. Furthermore, planting spruce re-
quires just as much site preparation as
natural seeding. Many planting failures in
the Rocky Mountains can be traced to one or
more of the disadvantages mentioned above
(Roe et al. 1970).

2. Site Preparation. — Site preparation for
spruce plantations probably requires more
consideration than for most other species
because of the complex relationship between
the environment and seedling requirements.
For example, warmer soils and increased
moisture availability accompanying com-
plete vegetation removal would benefit
seedlings, but because of their sensitivity,
seedlings would be more prone to severe in-
jury from intense light and frost. Therefore,
in the absence of logs or stumps, live vegeta-
tion such as willows, Potentilla, fireweed,
Vaccinium, or other species of similar
growth habit may be desirable as protective
cover even though it competes with seed-
lings.

Hand scalping will probably be adequate
for most planting operations. Hand-scalped
spots should not be smaller than 18 to 24
inches square. Above-ground parts of plants
are totally removed, but lateral roots from
vegetation surrounding the scalp usually
remain active. Thus the zone of soil released
from the competitive effects of vegetation
tapers rapidly below the ground surface.

Heavy concentrations of slash should be
treated to reduce fire and insect hazards and
adverse visual impacts, but slash disposal
and seedbed preparation with heavy
machinery should be minimized. Removing
vegetative competition or treating slash can
adversely affect plantation establishment by

destroying microsites that afford protection
for planted seedlings. Machines could be
used, however, to obtain better distribution
of favorable microsites over the plantation
by rearranging logs. Exposure of mineral
soil during such operations would also create
favorable seedbeds, which might result in
supplemental stocking from natural regen-
eration.

In areas where hand scalping is unsatis-
factory because of dense sod-forming
grasses and sedges or a heavy cover of her-
baceous species such as Mertensia, vegeta-
tion may be controlled by such machine
methods as disking, furrowing, mounding,
ridging (berms resulting from plowing), and
bulldozing. Where competing vegetation
consists of relatively tall brush species that
form dense cover, complete removal or
cleared strips of bulldozer-blade widths may
be desirable. Machine scalping with disks or
plows (furrowing or ridging) should leave
vegetation-free areas 1.5 to 2 ft wide.

Broadcast burning can be used on areas
where there is no advanced reproduction or
residual stand. Logs not consumed in the fire
will provide shade for planted seedlings
(Roe et al. 1970).

Planting Stock. — Plant only stock that
meets the following specifications: (1) Tops
should be no shorter than 3 to 4 inches; they
should be well developed with not less than
two or three branches. (2) Roots should not
be shorter than 5 to 6 inches; they should be
compact, fibrous, and well developed with
several lateral roots. (3) Tops and roots
should have a low shoot/root ratio.

Planting Season. — Plant spruce in the
spring after snowmelt. Planting usually
should be completed before June 25, but may
be extended to July 10 if moisture does not
become depleted or temperatures unseason-
ably high. Temporarily suspend planting
during the regular season when tempera-
tures are unseasonably warm, especially on
clear days when the wind is blowing.

Storage. — Nearly all planting in the central
and southern Rocky Mountains requires that
seedlings be lifted while they are still dor-
mant and stored at the nursery until planting
sites are free of snow. Because of the inci-
dence of mold and depletion of food re-
serves, spruce should not be held in storage
longer than 3 months. Seedlings must be
treated as dormant plants during transit to
planting sites. If refrigerated transport is
not available, cover the bundles or bags with

canvas to maintain temperatures between
34° to 40° F. Storage problems are more se-
vere in the field because limited facilities on
the planting site make temperature control
difficult. Well-insulated storage sheds that
can be cooled by ice or snow can be used in
the absence of mechanical refrigeration. If
such storage is not available, cool, moist cel-
lars or even snowbanks can be used. Seed-
lings can be held in storage locally up to 7
days if temperatures can be maintained
below 40° F.; otherwise limit local storage to
3 days. When transferring seedlings from
bundles or bags to planting containers,
handle the seedlings carefully to prevent
root breakage and do not expose roots to sun
or wind.

Spot Selection. — Plant seedlings with roots
in moist soil and only on those spots where
seedlings are protected by stumps, logs,
slash, or open cover of live vegetation, and
only on the north and east side of protective
cover (fig. 15). Avoid planting in depres-

Figure 1 5. — Good spot selection. Engelmann spruce seed-
ling planted on the east side of a log where shade is
fully utilized.

sions, frost pockets, on small mounds, in
areas with an extensive cover of sod-forming
vegetation, where advanced regeneration
shows evidence of snow mold, and where
skidding and slash disposal have buried
trash in the soil.

7. Planting Method. — Use the hole method;
dig holes with mattock hand tools or power
augers. If power augers are used, do not dig
holes too far in advance of planting.

8. Plantation Protection. — Protect new plant-
ings from trampling by livestock until seed-
lings are at least 3 ft high. They may re-
quire fencing or other adjustments in graz-
ing allotments. New plantings should also be
protected from rodents. Sample the rodent
populations on the areas scheduled to be
planted. If populations are large, provide
controls until seedlings become established.

9. Records. — Adequate data from detailed re-
cords are needed to (1) correct deficiencies
causing failure, and (2) recognize good prac-
tices leading to successful plantations. Deci-
sions affecting regeneration practices can
then be based on quantitative information
rather than conjecture. Follow the recom-
mendations suggested by Ronco (1972).

Seeding. — Until reliable techniques have
been worked out for the central and southern
Rocky Mountains, direct seeding of spruce is
not recommended as an operational regenera-
tion practice.

PARTIAL CUT AREAS

Partial cutting here includes both shelter-
wood and selection cuts and their modifications.
They are regeneration systems that harvest the
timber on an area in more than one step. From a
silvicultural point of view these are acceptable
harvesting methods in old-growth spruce-fir.

They are, in fact, the only options open to the
manager where (1) multiple use considerations
preclude clearcutting, (2) combinations of small
cleared openings and high forests are required
to meet the needs of various uses, or (3) areas
are difficult to regenerate after clearcutting.
However, windfall, insects, and stand condi-
tions impose limitations on how stands can be
handled. A careful appraisal of the capabilities
and limitations of each stand is necessary to
determine cutting practices. Furthermore, par-
tial cutting requires careful marking of indi-
vidual trees or groups of trees to be removed,
and close supervision of logging.

A classification based on stand characteris-
tics is needed to (l)identify the kinds of stands
that can be partially cut, those that must be
clearcut and started new, and those that should
be uncut; and (2) develop partial cutting prac-
tices for different management objectives.
Until such a classification is available, the fol-
lowing recommendations for partial cutting
practices are keyed to broad stand descriptions
based largely on experience, windfall risk situa-
tions, and insect problems (Alexander 1973).
Practices needed to obtain natural reproduction
are also discussed.

Single-Storied Stands12
Description. —

1. Stands may appear to be even-aged (fig. 16),
but usually contain more than one age class.
In some instances, the canopy may not ap-
pear to be of a uniform height because of
changes in topography, stand density, or
stocking.

2. Codominant trees form the general level of
the overstory canopy. Dominants may be 5 to

^Reproduction less than 4.5 ft tall is not considered a
stand story in these descriptions.

SINGLE -STORY

Figure 16.— A single-storied spruce-fir stand.

10 ft taller, and occasionally predominants
may reach 15 to 20 ft above the general
canopy level. Taller intermediates extend
into the general canopy; shorter inter-
mediates are below the general canopy level
but do not form a second story.

3. The range in diameters and crown length of
dominants and codominants is small.

4. There are few coarse-limbed trees in the
stand; if two-aged or more, younger trees
usually have finer branches and may not
have diameters equal to the older trees.

5. Trees are more often uniformly spaced than
clumpy.

6. A manageable stand of advanced reproduc-
tion usually is not present.13

7. If lodgepole is present in the overstory it is
not a major stand component. Lodgepole
pine reproduction is absent or sparse.

Recommended Cutting Treatments. — These
stands are usually the least windfirm because
trees have developed together over a long
period of time and mutually protect each other
from the wind.

1. If the windfall risk is below average, and the
trees are uniformly spaced —

a. The first cut should be light, removing
about 30 percent of the basal area of the
stand on an individual tree basis.14 This
type of cutting resembles the first or
preparatory cut of a three-step shelter-
wood. Since all overstory trees are about
equally susceptible to windthrow, the
general level of the canopy should be
maintained by removing some trees from
each overstory crown class. Those trees
with known indicators of defect should be
removed first, but avoid creating open-
ings in the canopy with a diameter larger
than one tree height by distributing the
cut over the entire area. Furthermore, do
not remove dominant trees in the interior
of the stand that are protecting other
trees to their leeward if these latter trees
are to be reserved for the next cut. In
these and all other stands described

,3Since any kind of cutting may destroy as much as
half of the advanced reproduction, even with careful log-
ging, at least 600 spruce or fir seedlings and saplings per
acre, of good form and vigor and free of defects, must be
present to be considered a manageable stand.

l4As a practical matter, small saplings that do not
represent significant competition to the remainder of the
stand may be excluded from the computation of basal
area.

where natural openings one to several
acres occur, leave the trees around the
perimeter for a distance of about one tree
height until the final entry. These trees
have been exposed to the wind and are
usually windfirm, and protect the trees in
the interior of the stand.

b. The second entry into the stand should not
be made for at least 5 to 10 years after the
first cut in order to determine if the re-
sidual stand is windfirm. This cut should
also remove about 30 percent of the origi-
nal basal area on an individual tree basis.
It simulates the second or seed cut of a
three-step shelterwood. The largest and
most vigorous dominants and codomi-
nants should be reserved as a seed
source, but avoid cutting openings in the
canopy larger than one tree height in
diameter by distributing the cut over the
entire area, even if it means leaving trees
with poor seed production potential.

c. The last entry is the final harvest and
should remove all of the remaining origi-
nal overstory. It should not be made until
a manageable stand of reproduction has
become established, but the cut should
not be delayed beyond this point if timber
production is one of the primary concerns
because the overwood hampers the later
growth of seedlings.

d. The manager also has the option of re-
moving less than 30 percent of the basal
area at any entry and making more en-
tries, but they cannot be made more often
than every 5 to 10 years. This will spread
the cut out and maintain a continuous
forest cover for a longer period of time.

2. If the windfall risk is below average, and the
trees are clumpy —

a. The first cut should be a modified group
selection that removes about 30 percent
of the basal area. Harvesting timber in
groups will take advantage of the natural
arrangement of trees in clumps. Group
openings should be kept small — not
more than one to two tree heights in
diameter — and not more than one-third
of the area should be cut over (fig. 17).
However, all trees in a clump should be
either cut or left since they mutually sup-
port each other, and removing only part
of a clump is likely to result in windthrow
of the remaining trees.

b. The second entry into the stand should not
be made until the first group of openings
has regenerated. This cut can also re-
move about 30 percent of the original

Figure 1 7.— Group-selection cutting in spruce-fir. One-third of the area was cut in openings about
one tree height in diameter. Fraser Experimental Forest, Colorado.

basal area without cutting over more than
an additional one-third of the area. Open-
ings should be no closer than about one to
two tree heights to the openings created
by the previous cut.

c. The final entry should remove the re-
maining groups of merchantable trees.
The timing of this cut depends upon how
the manager elects to regenerate the new
openings. If he chooses to use natural re-
generation the final harvest must be de-
layed until the regeneration in the open-
ings cut earlier are large enough to pro-
vide a seed source.

d. The manager may choose to remove less
than 30 percent of the basal area and cut
over less than one-third of the area at any
one time. This will require more entries,
but each new cut should not be made until
the openings cut the previous entry have
regenerated. Furthermore, the last
groups cannot be cut until there is either a
seed source or the manager elects to plant
these openings.

If the windfall risk is above average, and the
trees are uniformly spaced —

a. The first cut should be restricted to a very
light preparatory cutting that removes
about 10 percent of the basal area on an

individual tree basis. The objective is to
open up the stand, but at the same time
minimize the windfall risk to the remain-
ing trees. This type of cutting resembles a
sanitation cut in that the poorest risk
trees — those of low vigor and with
known indicators of defect — and pre-
dominants should be removed, but it is
important that the general level of the
overstory canopy be maintained intact.
Provision should be made to salvage
windfalls after spruce beetle flight at the
end of July.

b. The second entry can be made in about 10
years after the first cut. This entry should
remove about 15 to 20 percent of the orig-
inal basal area on an individual tree basis.
Any windfall salvaged after the first cut
should be included in the computation of
the basal area to be removed. The objec-
tive of this preparatory cut is to continue
to open up the stand gradually while pre-
paring the stand for the seed cut. Most of
the trees marked for removal should
come from the intermediates and small
codominants, but maintain the general
level of the canopy intact.

c. It will require another 5 to 10 years to
determine if the stand is windfirm
enough to make another entry. This will
be the seed cut, and should remove about

20 to 25 percent of the original basal area
including any windfalls salvaged since
the last cutting. The largest and most vig-
orous dominants and codominants should
be reserved as a seed source, but it is
more important to distribute the cut over
the entire area,
d. The last entry is the final harvest to re-
move the remaining original overstory. It
cannot be made until a manageable stand
of reproduction has been established.
About 50 percent of the original basal
area will be removed in this cut, and if this
is more than 10,000 fbm per acre, it is
probably too heavy to be removed in one
harvest without undue damage to the re-
production. The manager must therefore
plan on a two-step final harvest. The sec-
ond step can begin as soon as the skidding
is finished in the first step, providing that
a manageable stand of reproduction still
exists.

If the windfall risk is above average and the
trees are clumpy —

a. The first cut should be light, removing
about 15 to 20 percent of the basal area in
a modified group selection. Group open-
ings should be no larger than one tree
height in diameter, and not more than
one-fifth of the area should be cut over at
any one time. All trees in a clump should
be cut or left. In stands with small natural
openings — about one tree height in
diameter — the openings can be enlarged
one tree height by removing clumps of
trees to the windward.

b. Four additional entries into the stand can
be made at periodic intervals, but each
new entry should not be made until the
openings cut the previous entry have re-
generated. The last groups to be removed
should be retained until the original

group openings are large enough to pro-
vide a seed source. About 20 percent of
the basal area should be removed over
about one-fifth of the area at each entry.
Group openings should be no larger than
one tree height in diameter.

5. If the windfall hazard is very high —

The choice is limited to removing all the
trees or leaving the area uncut. Cleared
openings should not be larger than regenera-
tion requirements dictate, and they should
be interspersed with uncut areas of at least
equal size. Not more than one-third of the
total area in this wind risk situation should be
cut over at one time.

Two-Storied Stands
Description. —

1. Stands may appear to be two-aged (fig. 18),
but usually contain more than two age
classes.

2. The top story (dominants, codominants, and
intermediates) is usually spruce; resembles
a single-storied stand.

3. The second story is often fir, and the trees
are younger and smaller in diameter than the
overstory. It may consist of small saw logs,
poles, or large saplings, but is always below
the top story and clearly distinguishable
from the overstory. Trees in the second story
are overtopped, but not suppressed.

4. There may be a manageable stand of ad-
vanced reproduction.

5. Arrangement of individual trees varies from
uniform to clumpy.

6. If lodgepole pine is present in the stand it is
usually a scattered component of the over-
story. Lodgepole pine reproduction is absent
or sparse.

TWO- STORY

Figure 18. — A two-storied spruce-fir stand.

Recommended Cutting Treatments. — Same
as for three-storied stands.

Three-Storied Stands
Description. —

1. Stand may appear to be three-aged (fig. 19),
but usually contains more than three age
classes. Occasionally two-aged, but is never
all-aged.

2. If the stand is three-aged or more, the top
story is usually predominantly spruce and
resembles a single-storied stand except that
there are fewer trees. The second and third
stories are usually younger and smaller
diameter trees (small saw logs, poles, and
large saplings) that are usually fir. In a typi-
cal stand, the second story will be 10 to 30 ft
below the top story and consist of small saw
logs or large poles. Third story will be 10 to
30 ft below the second story and consist of
small poles or large saplings. Although the
second and third stories are overtopped, the
trees are usually not suppressed.

3. If two-aged, the first two stories are old-
growth with spruce in the top story and fir in
the second story. The third story will be
younger trees, largely fir, of smaller diame-
ter.

4. Frequently contains a manageable stand of
advanced reproduction.

5. More often clumpy than are single- or two-
storied stands.

6. If lodgepole pine is present, it is usually a
scattered component of the top story, but
may occur in the second story. Lodgepole
pine reproduction is usually absent or
sparse.

Recommended Cutting Treatments (Two- and
Three-Storied Stands). — Trees in the overstory
are usually more windfirm than those in single-
storied stands. The second and third stories are
likely to be less windfirm than the top story.

1. If the windfall risk is below average, and the
trees are uniformly spaced —

a. The first cut can remove about 40 percent
of the basal area where there is not a
manageable stand of advanced reproduc-
tion. This type of cutting is heavy enough
to resemble the first step or seed cut of a
two-cut shelterwood, but the marking fol-
lows the rules for individual tree
selection — mature trees are removed
from each story. Since the overstory is
likely to be more windfirm, selected
dominants and codominants of good
vigor and free of defect should be left.
These trees are also the most desirable
seed source. Avoid cutting holes in the
canopy larger than one tree height in
diameter by distributing the cut over the
entire area. Furthermore, do not remove
dominant trees from the interior of the
stand that are protecting other trees to
their leeward if these latter trees are to be
reserved for the next cut.

b. The second entry should be the final har-
vest to remove the remaining original
stand and release the reproduction. It
cannot be made until the new stand of
reproduction is established. If the residu-
al volume is greater than about 10,000 fbm
per acre, the final harvest should be made
in two steps to avoid undue damage to
newly established reproduction. The sec-
ond step can begin as soon as the skidding
is finished in the first step, providing that
a manageable stand of reproduction still
exists.

c. If there is a manageable stand of ad-
vanced reproduction, the first cut can be
an overstory removal if the volume is not
too heavy. Otherwise, the first cut can
remove 40 percent of the basal area on an
individual tree basis as long as the more
windfirm dominants and codominants are
left. The timing of the second cut is not
critical from a regeneration standpoint,

THREE- STORY

Figure 19. — A three-storied spruce-fir stand.

providing a manageable stand of repro-
duction still exists after the first cut.
d. The manager has other options to choose
from. He may elect to cut less than the
recommended basal area, make more en-
tries, and spread the cut out over a longer
period of time by delaying the final har-
vest until the new stand is tall enough to
create a continuous high forest. He may
also elect to convert these stands to an
uneven-aged structure by making a
series of light cuts — 10 to 20 percent of
the basal area — at frequent
intervals — 10 to 20 years. Ultimately the
stand will contain a series of age classes.

2. If the windfall risk is below average, and the
trees are clumpy —

a. The first cut should remove about 40 per-
cent of the basal area in a modified group
selection cutting. The group openings can
be larger (two to three times tree height)
than for single-storied stands, but the
area cut over should be not more than
one-third of the total. Furthermore, the
group openings should be irregular in
shape, but without dangerous windcatch-
ing indentations in the edges. All trees in a
clump should either be cut or left.

b. Two additional entries can be made. They
should each remove about 30 percent of
the original basal area in group openings
up to two to three times tree height, but
not more than one-third of the area should
be cut over at any one time. If there is not
a manageable stand of advanced repro-
duction, the manager must wait until the
first group of openings is regenerated be-
fore cutting the second series. Further-
more, he must either delay the cutting of
the final groups until there is a seed
source or plan on planting these openings.
If there is a manageable stand of ad-
vanced reproduction, the timing between
cuts is not critical from a regeneration
standpoint.

c. The manager has the option of removing
less than the recommended basal area
and cutting less than the recommended
area at any one time. This will require
more entries and spread the cut out over a
longer period of time.

3. If the windfall risk is above average, and the
trees are uniformly spaced —

a. The first cut should be a light preparatory
cutting that removes not more than 20
percent of the basal area, on an individual

tree basis, where there is not a manage-
able stand of advanced reproduction.
Predominants, intermediates with long
dense crowns, and trees with known indi-
cators of defect should be removed first,
but maintain the general level of the
canopy. The objective of this cut is to
open up the stand, but at the same time
minimizing the windfall risk to remaining
trees. Provision should be made to sal-
vage windfalls after spruce beetle flight.

b. The second entry into the stand should not
be made in less than 10 years. This cut
should remove about 30 percent of the
original basal area, including the salvage
of any windfalls that occur between the
first and second cuts. The second entry is
the seed cut, therefore the best dominants
and codominants should be reserved as a
seed source, but it is important that the
cut be distributed over the entire area.

c. The next entry is the final harvest to re-
move the remaining merchantable vol-
ume and release the new reproduction
after it has become established. How-
ever, if the residual stand has too heavy a
volume, the final harvest should be made
in two steps.

d. If these stands contain a manageable
stand of reproduction and the volume per
acre is not too heavy, the first cut can be
an overwood removal. If the volume is too
heavy for a one-step removal, the man-
ager should follow the recommendations
above because the wind hazard is too
great to permit a two-step removal in a
stand that has not been previously opened
up.

4. If the windfall risk is above average, and the
trees are clumpy —

a. The first cut should be a modified group
selection that removes about 25 percent
of the basal area. Group openings should
be kept small — not more than one to two
tree heights in diameter — and not more
than one-fourth of the area should be cut
over at any one time. All trees in a clump
should either be cut or left. Small natural
openings can be enlarged one to two tree
heights by removing trees in clumps to
the windward of the opening.

b. Three additional entries should be made.
If there is not a manageable stand of ad-
vanced reproduction, about 25 percent of
the original basal area should be removed
on about one-fourth of the area in each
entry. The interval between cuts will de-
pend upon the time required to regener-

ate each series of openings. The manager
must either delay the removal of the final
groups until a seed source is available or
plant the openings. If there is a manage-
able stand of advanced reproduction, the
timing between cuts is not critical from a
regeneration standpoint.

5. If the windfall hazards are very high —

The choice is usually limited to removing all
the trees or leaving the area uncut. Cleared
openings should not be larger than regenera-
tion requirements dictate, and should be in-
terspersed with uncut areas. Not more than
one-third of the total area in this windfall
risk situation should be cut over at any one
time.

Multi-Storied Stands
Description. —

1. Stands are generally uneven-aged (fig. 20)
with a wide range in diameters.

2. If the stand developed from a relatively few
individuals, overstory trees are coarse
limbed and fill-in trees are finer limbed. The
overstory trees may be relatively vigorous.

3. If the stand developed from the deteriora-
tion of a single- or two-storied stand, the
overstory may be no limbier than the fill-in
trees. Much of the vigorous growing stock is
below saw log size.

4. There is almost always a manageable stand
of reproduction as a ground story.

5. The fill-in trees may be clumpy, but usually
the overstory trees are uniformly spaced.

6. Lodgepole pine may occur as a scattered
component of the stand, usually in the over-
story, but it may also occur in all stories in-
cluding reproduction.

Recommended Cutting Treatments. — These
are usually the most windfirm stands, even
where they have developed from the deteriora-
tion of single- and two-storied stands, because
by the time they have reached their present
condition the remaining overstory trees are
usually windfirm.

1. If the windfall risk is below average —

There is considerable flexibility in harvest-
ing these stands. All size classes can be cut,
with emphasis on either the largest or small-
est trees in the stand. For example, the first
cut can range from removal of all large trees
in the overstory to release the younger grow-
ing stock, to a thinning from below to im-
prove the spacing of the larger trees. If the
manager elects to make an overwood re-
moval and the volume is too heavy, it should
be harvested in two steps. Thereafter, cut-
ting can be directed toward either even- or
uneven-aged management, with entries
made as often as growth and regeneration
needs dictate.

2. If the windfall risk is above average or very
high —

The safest first cut is an overwood removal
with a thinning from below to obtain a widely
spaced, open-grown stand that will develop
windfirmness. Thereafter, cutting can be di-
rected toward either even- or uneven-aged
management.

Modifications to Cutting Treatments
Imposed by Spruce Beetles

1. If spruce beetles are present in the stand at
an endemic level, or in adjacent stands in
sufficient numbers to make successful at-
tacks, and:

MULTI- STORY

Figure 20. — A multi-storied spruce-fir stand.

a. Less than the recommended percentage
of basal area to be removed is in suscepti-
ble trees, any attacked and all susceptible
trees should be removed in the first cut.
This will include most of the larger
spruce trees and is a calculated risk,
especially in above-average wind risk
situations. Furthermore, the percentage
of fir in the stand will increase. Provision
should be made to salvage attacked trees.
The remaining cuts should be scheduled
in accordance with windfall risk, insect
susceptibility, and regeneration needs.

b. More than the recommended percentage
of basal area to be removed is in suscepti-
ble trees, the manager has three options:
(1) remove all the susceptible trees, (2)
remove the recommended basal area in
attacked and susceptible trees and accept
the risk of future losses, or (3) leave the
stand uncut. If the stand is partially cut or
left uncut, surviving spruce would prob-
ably make up at least half of the residual
basal area, but most of the merchantable
spruce would be small-diameter trees.

2. If the stand is sustaining an infestation that
is building up and the manager chooses to
either partially cut or leave the stand uncut
because clearcutting is unacceptable, he
must accept the risk of an outbreak that will
destroy most of the merchantable spruce in
the stand and spread to adjacent stands.

Cutting to Save the Residual

Before any cutting begins, the manager must
determine whether he has an acceptable stand
of advanced reproduction and if he is going to
manage it. Furthermore, he must reevaluate the
stand after the final harvest and slash disposal
to determine the need for supplemental stock-
ing. The same criteria used to evaluate ad-
vanced reproduction on clearcut areas apply
here.

and other logging equipment to the skidroads.
In shelterwood cuttings, trees should be felled
into openings as much as possible using a her-
ringbone pattern that will permit logs to be
pulled onto the skidroads with a minimum of
disturbance. It may be necessary to deviate
from the herringbone felling angle in order to
drop trees into openings. If this is the case, the
logs will have to be bucked into short lengths
to reduce skidding damage. Trees damaged
in felling and skidding should not be removed
if they are still windfirm. In group-selection
cutting, the felling pattern should be similar
where there is a manageable stand of advanced
reproduction. Otherwise all trees should be
felled into the openings. Both shelterwood and
group-selection cuttings require close coordi-
nation between felling and skidding because it
may be necessary to fell and skid one tree
before another tree is felled.

Slash Disposal and Seedbed Preparation

Some slash disposal will probably be needed
after each cut, but it should be confined to con-
centrations and that needed to reduce visual
impact because most equipment now available
for slash disposal is not readily adaptable to
working in shelterwood cuttings. Furthermore,
burning of slash will cause additional damage to
the residual. Skid out as much of the down sound
dead and green cull material as possible for dis-
posal at the landings or at the mill. Some hand
piling or scattering may be needed where slash
disposal equipment cannot be used. In group-
selection cutting, if there is not a manageable
stand of advanced reproduction, dozers e-
quipped with bush blades can be used to concen-
trate slash for burning in the openings. Piles
should be kept small to reduce the amount of
heat generated. Leave some of the larger pieces
of slash and other debris in place to provide
shade for new seedlings. Cut green spruce
material larger than 8 inches in diameter
should be removed to reduce the buildup of
spruce beetle populations.

On areas to be regenerated by new reproduc-
tion, a partial overstory canopy or trees stand-
ing around the margins of small openings pro-
vide two of the basic elements necessary for
regeneration success — a seed source within
effective seeding distance, and an environment
compatible with germination, initial survival,
and seedling establishment. The manager must
make sure that the third element — a suitable
seedbed — is provided after the seed cut where
shelterwood cutting is used, and after each cut
where group selection is used. If at least 40 per-
cent of the available ground surface is not ex-

posed mineral soil after logging and slash dis-
posal, additional seedbed preparation is needed.
Until special equipment is developed, the same
problem exists as with slash disposal. The
equipment available today is too large to work
well around standing trees. Smaller machines
equipped with suitable attachments will have to
be used, but they must be closely supervised to
minimize damage to the residual.

Multiple-Use Silviculture

In addition to being the most productive
timber type in the central Rocky Mountains,
spruce-fir forests are also the highest water
yielding, and are valuable wildlife, recreation,
and scenic areas. Because of increasing de-
mands on forest lands from a rapidly expanding
population and the limited resource available,
management must consider all key land uses.
The kinds of stands that appear desirable for
increased water yields, preservation of the
forest landscape, maintenance of scenic values,
and improvement of wildlife habitat have been
suggested in a general way by both research and
observation.

WATER

Water yield studies have indicated that the
increase in snow depth in openings cut in
spruce-fir forests is not additional snow but a
change in deposition pattern (Hoover and Leaf
1967). Snow blows off adjacent standing trees
and settles in the openings. The increased snow
in the openings means that more water is avail-
able for streamflow. Research and experience
suggest that a round or patch-shaped opening
with a diameter about five to eight times the
height of surrounding trees is the most effec-
tive for trapping snow (Hoover 1969). In larger
openings, wind dips to the ground and scours
and blows snow out of the opening. About one-
third of the forest area should be in openings,
which would be periodically recut when tree
height reaches one-half the height of surround-
ing trees. The remaining two-thirds of the area
would be retained as continuous high forest;
trees would be periodically harvested on an
individual-tree basis. Ultimately the reserve
stand would approach an all-aged structure with
the overstory canopy remaining at about the
same height, although the original overstory
could not be maintained indefinitely.

An alternative would be to make a light cut
distributed over the entire watershed, remov-
ing about 20 to 30 percent of the basal area on an
individual-tree basis or in small groups. The ob-

jective would be to open up the stand enough to
develop windfirmness, and salvage low-vigor
and poor-risk trees. Openings five to eight
times tree height can then be cut on about one-
third of the area. The remaining two-thirds of
the area would be retained as permanent high
forest, with trees periodically removed on an
individual-tree basis or in small groups.

Another alternative that would integrate
water and timber production would be to har-
vest all of the old-growth in a cutting block in a
series of cuts spread over a period of 120 to 160
years. Each cutting block would contain at least
300 acres, subdivided into round or patch-
shaped units approximately 2 acres in size or
four to five times (in diameter) the height of a
general canopy level. At periodic intervals,
some of these units, distributed over the cutting
block, would be harvested and the openings re-
generated. The interval between cuttings could
vary from as often as every 10 years to as infre-
quently as every 30 to 40 years. The percentage
of units cut at each interval would be deter-
mined by Cutting cycle/Rotation age x 100. At
the end of one rotation, each cutting block would
be composed of groups of trees in several age
classes ranging from reproduction to trees
ready for harvest. The tallest trees would be
somewhat shorter than the original overstory,
but any adverse effect on snow deposition
should be minimized by keeping the openings
small and widely spaced.

WILDLIFE

Big-game use of spruce-fir forest lands can be
improved by certain timber cutting practices,
as shown in two recently completed studies.
Openings of less than 20 acres cut in the canopy
of spruce-fir forests in Arizona were heavily
used by deer and elk, but use decreased
considerably in larger openings (Reynolds
1966). Openings created by harvesting were
preferred to natural openings because the
vegetation that initially comes in on cutovers
is more palatable to deer and elk. Reynolds
suggested that openings be maintained by
cleaning up the logging slash and debris, remov-
ing new tree reproduction, and seeding the area
to forage species palatable to big-game. How-
ever, since natural succession on the cutover
areas is likely to replace the more palatable
species eventually, a more desirable alternative
would be to cut new openings periodically while
allowing the older cuttings to regenerate. That
would provide a constant source of palatable
forage and the edge effect desired, while creat-
ing an all-aged forest by even-aged groups. The
openings created should be widely spaced, with

the stand between openings maintained as high
forest.

On the Fraser Experimental Forest in Col-
orado, deer use in spruce-fir forests was greater
and forage more abundant on cleared openings
than in the uncut forest. Clearcut openings 3
chains wide were used more than wider or nar-
rower strips (Wallmo 1969, Wallmo et al. 1972).
While no recommendations were made as to op-
timum size or arrangement of openings, the
Fraser study suggests that they be kept small
and interspersed with standing trees that could
be periodically harvested on an individual-tree
basis.

One alternative that would integrate wildlife
habitat improvement with timber production
would be to cut about one-sixth of a cutting
block every 20 years in openings about four to
five times tree height. Each Working Circle
would be subdivided into a number of cutting
blocks (of at least 300 acres) so that not all
periodic cuts would be made in a single year on a
Working Circle. Such periodic cutting would
provide a good combination of numbers and
species of palatable forage plants and the edge
effect desired, while creating a several-aged
forest of even-aged groups.

Wildlife other than big-game is also influ-
enced by the way forests are handled. For ex-
ample, with the curtailment of wildfires, some
reduction in stand density by logging is proba-
bly necessary to create or maintain drumming
grounds for male blue grouse (Dendragapus
obscurus Say). Partial cutting that opens up the
canopy enough to allow tree regeneration to es-
tablish in scattered thickets appears to provide
the most desirable habitat. Cutting small, ir-
regularly shaped openings (up to 10 acres) in the
canopy may also be beneficial to blue grouse, if
thickets of new reproduction become estab-
lished in the cleared openings (Martinka 1972).

RECREATION AND ESTHETICS

Permanent forest cover at least in part is pre-
ferred in recreation areas, travel influence
zones, and scenic view areas. Since old-growth
spruce-fir forests will not maintain themselves
in an esthetically pleasing or sound condition
indefinitely, some form of partial cutting would
maintain forest cover while at the same time
replacing the old with a new stand. However,
the visual impact of logging operations — haul
roads, damage to residual trees, and slash and
debris — must be minimized. In situations
where there is no alternative to clearcutting,
and the environmental impact of clearcutting is
unacceptable, there is no choice but to leave the
stands uncut.

To reduce the sudden and severe visual im-
pact on the landscape viewer, openings cut in
stands for timber and water production, wildlife
habitat improvement, and recreation (ski runs)
should be a repetition of natural shapes, visually
tied together to create a balanced, unified pat-
tern that will complement the natural landscape
(Barnes 1971). This is especially important for
those openings in the middle and background
that can be seen from distant views. The fore-
ground should be maintained in high forest
under some partial cutting system.

Silvicultural practices must be developed
that will incorporate the maintenance of scenic
values and provide the combination of continu-
ous high forest and cleared openings necessary
to integrate all land uses. This development will
include: (1) classifying existing stands into
categories of similar stand characteristics as a
means of identifying management potentials,
and (2) testing silvicultural systems and cul-
tural practices in stands of different charac-
teristics for a variety of management objec-
tives.

THE LODGEPOLE PINE TYPE

CHARACTERISTICS OF THE TYPE

The lodgepole pine type is generally pictured
as an even-aged, single-storied, overly dense
forest, varying in age from place to place but
uniform in age within any given stand. This is
true only where favorable fire, seed, and clima-
tic conditions once combined to produce a large
number of seedlings at one time (Lexen 1949).
Elsewhere, lodgepole pine grows on a wide
range of sites with a great diversity of stand
conditions. It can occur as two-aged, single- or
two-storied stands; three-aged, two- or three-
storied stands; and even-aged to broad-aged
multi-storied stands (Tackle 1954a, 1955).
Multi-storied stands, and to a lesser extent, two-
and three-storied stands, generally resulted
from either scattered trees that produced seed
for subsequent stand development, or the
gradual deterioration of old-growth stands from
wind, insects, and diseases (Alexander 1972).
The diversity complicates the modification of
silvicultural systems for multiple use.

Lodgepole pine stands are frequently pure
pine over much of the area it occupies, espe-
cially where stands originated after repeated
fires and there is no seed source for other
species (Tackle 1961a, 1965). However, mixed
stands of lodgepole pine and other species are
not uncommon. In pure stands of lodgepole pine
of medium to high density, there is seldom an
understory of reproduction; in low-density

Figure 21. — Heavy blowdown in lodgepole pine after partial cutting that removed 60 percent of
the original basal area. Fraser Experimental Forest, Colorado.

stands there may be younger trees in the under-
story. If this advanced growth has not been sup-
pressed for long periods of time it will respond
to release.

In mixed stands, the overstory can either be
pure pine, or pine, spruce and/or fir at higher
elevations, and pine and Douglas-fir at lower
elevations, with the climax species in the under-
story. Advanced growth of the climax species
will respond to release when the overstory is
removed (Alexander 1972).

PAST CUTTING HISTORY

Cuttings in lodgepole pine forests date back
almost 100 years. Some of the earliest were
clearcuttings to provide stulls, lagging, and
charcoal for mining operations. Pioneer ranch-
ers used lodgepole pine for fuel, fences, and
corrals. Later, millions of cross ties were hewn
for the railroads. Following World War I, some
form of partial cutting became standard prac-
tice on the National Forests of the central Rocky
Mountains, even though early studies suggested
that clearcutting satisfied the silvical require-
ments of the species (Bates et al. 1929, Clements
1910, Mason 1915b). The usual practice was to
mark stands for the selective removal of special
products. Cutting was often heavy because ev-
erything salable was frequently marked for

removal. Most skidding was done with horses,
and seedbed preparation was limited to the dis-
turbance associated with logging and slash dis-
posal. Slash was either lopped and scattered or
piled and burned (Thompson 1929).

Heavy partial cutting in general (removal of
more than 50 percent of the total basal area),
and under some conditions any kind of partial
cutting, was not successful as a means of arrest-
ing deterioration in old-growth stands or ac-
celerating growth of the residual stand. For ex-
ample, residual trees on the Fraser Experimen-
tal Forest suffered heavy mortality when about
60 percent of the total basal area was removed
by either individual tree selection or modified
seed-tree cutting (Alexander 1966b) (fig. 21).
Furthermore, net increment was less than in
uncut stands. Similar results followed heavy
partial cutting elsewhere in the central Rocky
Mountains, and in the northern and C inadian
Rockies (Blyth 1957, Hatch 1967, LeBarron
1952). Even where mortality was not a serious
problem, heavy partial cutting often left the
older, decadent stands in such poor condition
that not only was there little or no growing stock
available for another cut, but the stands had
little appearance of permanent forest cover
(Tackle 1965).

The principal cause of mortality was usually
windfall, and it generally increased as the in-
tensity of cutting increased. Mountain pine bee-

tie (Dendroctonus ponderosae Hopk.) outbreaks
caused heavy losses in some instances, and bee-
tles continue to be a serious and often unpre-
dictable threat to lodgepole pine forests. In ad-
dition, many stands were infected with dwarf
mistletoe (Arceuthobium americanum Nutt. ex.
Engel.). Partially opening up the stand inten-
sified the infection on residual trees, which in
turn infected the new reproduction, leading to
infection centers in the next generation. These
heavily dwarf mistletoe-infected stands are a
serious lodgepole pine management problem
(Gill and Hawksworth 1964).

Where substantial reserve volumes were left,
partial cutting was successful in some instances
in the sense that the residual stand did not blow
down. On the Fraser Experimental Forest,
windfall losses were light and other mortality
negligible after partial cutting removed about
45 percent of the total basal area by a modified
shelterwood cut, even though the stands were
exposed to windstorms that nearly destroyed
adjacent, partially cut stands with less residual
basal area (Alexander 1966b). Net increment
was no greater than in uncut stands, however.

There are numerous examples of early cut-
tings on many National Forests in Colorado and
Wyoming where a light to moderate shelter-
wood cut that removed 30 to 40 percent of the
total basal area did not result in excessive mor-
tality. The openings created have regenerated
to either new lodgepole pine or the climax

species. Where dwarf mistletoe infection in
overstory trees was light, the new pine stand is
not heavily infected. Similar stands have origi-
nated from open-grown trees and stands that
were opened up by mountain pine beetle infes-
tations (Alexander 1972).

In 1939, Taylor developed a tree classification
scheme for marking lodgepole pine for partial
cutting that is still useful today (fig. 22). He
based his classification on the area, length, and
vigor of the crowns of individual trees:

Vigor class A

1. Crown area: 30 percent or more of the "ex-
treme outline" of vigor class A.

2. Crown length: 50 percent or more of the bole
length.

3. Crown vigor: Dense, full, good color,
pointed.

Vigor class B

1. Crown area: Usually more than 30 percent
but less than 50 percent of the "extreme out-
line" of vigor class A.

2. Crown length: Usually more than 50 percent
but usually less than 60 percent of the bole
length.

3. Crown vigor: Moderately dense, good
color, pointed or slightly rounded.

Vigor class C

1. Crown area: 15 to 30 percent of the "ex-
treme outline" of vigor class A.

2. Crown length: 40 to 50 percent of the bole
length except for trees with above average
vigor, when 20 percent of the bole length is
sufficient.

3. Crown vigor: Sparse, bunchy, poor color,
never pointed.

Vigor class D

1. All live trees of poorer vigor than class C.
Includes trees in classes A, B, and C outlines
but with dead or dying tops.

At the close of World War II, harvesting
shifted back to clearcutting as the recom-
mended practice (LeBarron 1952, Lexen 1949).
Traditionally, stands have been clearcut in
either blocks or strips (Alexander 1966b,
LeBarron 1952, Lexen 1949, Tackle 1965). The
pattern and size of opening depended upon the
predominant cone habitat (serotinous or non-
serotinous) and the occurrence of dwarf mis-
tletoe (Tackle 1965). The common practice has
been to cut all merchantable trees, followed by
removal of the unmerchantable residual to re-
duce dwarf mistletoe infection. Slash and log-
ging debris have usually been either (1) broad-
cast burned, dozer piled or windrowed and
burned, or (2) roller chopped to reduce fire
hazard and prepare seedbeds. Clearcuts have
usually restocked naturally if logging slash
bearing serotinous cones was carefully handled
(Alexander 1966a; Boe 1956; Tackle 1964, 1965),
or openings were small where cones were non-
serotinous (Alexander 1966a). However, both
artificial and natural regeneration efforts have
failed where seed was burned in slash fires,
openings were too large to be seeded in from the
side, or opening up the site created difficult
microenvironments (USDA-FS 1971).

Clearcutting is still the recommended prac-
tice for areas where timber production is the
primary use, but openings must be smaller (40
acres or less) than in the past, and designed to
blend into the landscape. Where the visual and
environmental impacts of clearcutting are not
acceptable, clearcutting is not compatible with
other uses, or regeneration will be difficult,
some form of partial cutting must be used
(Alexander 1972).

DAMAGING AGENTS
Windfall

In the central Rocky Mountains, lodgepole
pine is generally considered susceptible to

windthrow after cutting. Partial cutting in-
creases the risk because the entire stand is
opened, whereas only the boundaries between
cut and uncut areas are vulnerable after clear-
cutting (Alexander 1966b, 1972; Mason 1915b).
While the tendency to windthrow is frequently
attributed to a shallow root system, the de-
velopment of the root system varies with soil
and stand conditions. On deep, well-drained
soils, trees have a better root system than on
shallow or poorly drained soils. With the same
soil conditions, the denser the stand the less
windfirm are individual stems, because trees
that have developed together in dense stands
over long periods of time mutually protect and
support each other and do not have the roots,
boles, and crowns to withstand exposure to the
wind if opened up drastically. The risk of blow-
down is also greater in stands with defective
roots and boles. The presence of old windfalls is
a good indication of lack of windfirmness.
Furthermore, regardless of how stands are cut
or the soil and stand conditions, the risk of
blowdown is greater on some exposures than
others. The following windfall risk situations
based on exposure have been identified by
Mason (1915b) and Alexander (1964, 1967a,
1972):

Low Windfall Risk Situations

1. Valley bottoms except where parallel to the
prevailing winds, and all flat areas.

2. All lower and gentle middle north- and east-
facing slopes.

3. All lower and gentle middle south- and west-
facing slopes that are protected by consider-
ably higher ground not far to windward.

Moderate Windfall Risk Situations

1. Valley bottoms parallel to the direction of
prevailing winds.

2. All lower and gentle middle south- and west-
facing slopes not protected to the windward.

3. Moderate to steep middle and all upper
north- and east-facing slopes.

4. Moderate to steep middle south- and west-
facing slopes protected by considerably
higher ground not far to windward.

High Windfall Risk Situations

1. Ridgetops.

2. Moderate to steep middle south- and west-
facing slopes not protected to the windward,
and all upper south- and west-facing slopes.

3. Saddles in ridgetops.

The risk of windfall in these situations is in-
creased at least one category by such factors as

poor drainage, shallow soils, and defective roots
and boles. All situations become high risk if ex-
posed to special topographic situations such as
gaps and saddles in ridges at higher elevations
to the windward that can funnel wind into the
area.

On clearcut units the leeward cutting bound-
aries are the most vulnerable, especially if they
are at right angles to the direction of wind-
storms.

Insects

Many species of insects infest lodgepole pine
(Keen 1952), but the mountain pine beetle
(Dendroctonus ponderosae Hopk.) is the most
serious pest in mature to overmature lodgepole
pine stands in the Rocky Mountains. Epidemics
have occurred throughout recorded history
(Roe and Amman 1970), and extensive out-
breaks are now in progress in northern Wyo-
ming. Less extensive, but severe outbreaks
are underway in southern Wyoming and north-
ern Colorado, where a large number of old-
growth stands that have been protected from
wildfires are now reaching a high degree of sus-
ceptibility to attack (Alexander 1972).

Mountain pine beetles feed and breed in the
phloem layer. The first indications of attack are
pitch tubes on the trunk where beetles have en-
tered, and boring dust in the bark crevices and
around the base of the tree. Trees successfully
attacked in the summer usually begin to fade
the following spring. Needles change from
green to yellow green, sorrel, and finally rusty
brown before dropping off (McCambridge and
Trostle 1972).

Not all stands are equally susceptible to at-
tack. Epidemic outbreaks are usually as-
sociated with stands that contain at least some
vigorous, thick-phloemed trees 14 inches in
diameter and larger (Cole and Amman 1969, Roe
and Amman 1970). As the larger trees are killed,
the beetles must attack smaller diameter trees
until the outbreak finally subsides because the
phloem of these trees is not thick enough to
provide a food supply. Trees smaller than 6 in-
ches d.b.h. are rarely killed. Although natural
factors such as a sudden lowering of fall tem-
perature or prolonged subzero winter temper-
atures, nematodes, woodpeckers, and parasites
may reduce populations, they cannot be relied
upon to control outbreaks (McCambridge and
Trostle 1972). Chemical control is expensive
and often is only a holding action until poten-
tially susceptible trees can be disposed of by
other means.

The only alternatives left to the manager in
heavily infested stands where most of the trees

are 10 inches in diameter and larger are to (1)
fell and salvage the infested trees, burn the
green culls and unmerchantable portions of
trees, and regenerate a new stand, or (2) let the
infestation run its course uncontrolled. On the
other hand, in infested stands with a good stock-
ing of trees in the smaller diameter classes, par-
tial cutting that removes the vigorous, larger
trees with thick phloem appears well adapted to
regulating mountain pine beetle losses.

The pandora moth (Coloradia pandora Blake)
(Carolin and Knopf 1968) and the lodgepole
terminal weevil (Pissodes terminalis Hopk.)
that produce distorted or forked crowns in
young stands are other potentially serious in-
sects attacking lodgepole pine.

Diseases

Dwarf mistletoe is the most serious disease
affecting lodgepole pine (Hawksworth 1965)
(fig. 23). Surveys in Colorado and Wyoming
show that from 30 to 60 percent of the commer-
cial lodgepole pine forests are infected to some
degree by dwarf mistletoe (Hawksworth 1958).
Dwarf mistletoe reduces growth, increases
mortality (Hawksworth and Hinds 1964), and
drastically reduces seed production. The mor-
tality rate depends largely on the age of the host
tree when attacked. Young trees die quickly,
while older trees with well-developed and vig-
orous crowns may not show appreciable effects
for years. Dwarf mistletoe is most damaging in
stands that have been partially opened up by
cutting, mountain pine beetles, or windfall, and
of least consequence on regenerated burns fol-
lowing catastrophic fires (Gill and Hawksworth
1964). Heavily infected old-growth stands fre-
quently have only about half the fbm volume of
comparable uninfected stands (Hawksworth
1958).

The disease is difficult to detect in recently
infected stands because trees show no abnor-
malities except for the inconspicuous shoots on
branches and main stems. Where the parasite
has been present for a long time, stands will
have one or more heavily damaged centers
characterized by many trees with witches'
brooms, spike-tops, and an above-average
number of snags with remnants of brooms (Gill
and Hawksworth 1964).

Although optimum development is favored by
a vigorous host, and the most vigorous trees are
most heavily infected, the frequency of infec-
tion is usually higher on poor than good sites.
Furthermore, where site index is 70 or greater
(Alexander 1966c), only the middle and lower
crowns of dominants and codominants are sus-
ceptible to heavy infection, while trees in the

Figure 23. — Dwarf mistletoe-infected lodgepole pine. Bighorn National Forest, Wyoming.

intermediate or lower crown classes are sus-
ceptible to heavy infection throughout their
crowns. Where the site index is below 70, all
crown classes are susceptible to heavy infection
throughout the crowns.15 In Colorado and
Wyoming, dwarf mistletoe has an altitudinal
limit about 300 to 500 feet below the upper limit
of commercial lodgepole pine forests. This
means that in some areas, considerable
lodgepole pine lies in a dwarf mistletoe-free
zone (Gill and Hawksworth 1964).

Separation of the old and new stands by clear-
cutting and felling unmerchantable residual
trees appears to be the best way to control dwarf
mistletoe. In areas of high tree values, such as
recreational, administrative, and homesites, in-
fected branches can be pruned from lightly in-
fected trees, but heavily infected trees must be
cut. Partial cutting and thinning generally
create ideal conditions for maximum damage,
and should be avoided where possible unless the
infection is light.

To quantify the severity of infection,
Hawksworth (1961) developed the 6-class mis-
tletoe rating system (fig. 24). The average stand
rating can be estimated by determining the per-

^'^Personal communication with Frank G.
Hawksworth, Plant Pathologist, Rocky Mt. For. and
Range Exp. Stn., Fort Collins, Colo.

centage of trees infected in the stand. The ap-
proximate relationship of average stand rating
to proportion of trees infected in several mature
stands was:

Average stand

Percent of

mistletoe

trees

rating

infected

100

Comandra blister rust, a canker disease
caused by Cronartium comandrae Pk., occurs
commonly in the central Rocky Mountains, but
damage has been most extensive in northern
Wyoming (Peterson 1962). Girdling causes dead
tops and flagging branches, which are the most
conspicuous symptoms until dead trees begin to
appear. On larger stem infections, cankers with
an abundance of yellow, dried resin are a con-
spicuous symptom (Mielke et al. 1968). The dis-
ease cannot pass directly from pine to pine but
requires an intermediate host (Comandra um-
bellata (L.) Nutt.).

The damage from Comandra rust is usually
not spectacular, but trees of all sizes and ages

INSTRUCTIONS

EXAMPLE

STEP I. Divide live crown into thirds.

STEP 2. Rote each third separately.
Each third should be given a
rating of 0, I or 2 as described
below.

(0) No visible infections.

(1) Light infection (1/2 or
less of total number of
branches in the third infected).

(2) Heavy infection (more
than 1/2 of total
number of branches in
the third infected).

STEP 3. Finally, add
ratings of thirds
obtain rating for
totol tree.

If this third has no visible
infections, its rating is (0).

If this third is lightly infected,
its rating is (I).

If this third is heavily
infected, its rating is (2).

The tree in
will receive
0+1 + 2 •

this example
a rating of
3.

Figure 24. — The 6-class mistletoe rating system (Hawksworth 1961).

are susceptible (Peterson 1962). Seedlings may
be killed in a relatively short time. In older
trees, the time betwen initial infection and
death may be 25 or more years because the in-
fection enters the trunk by way of the branches
and the rate of spread is slow. Under conditions
favorable to the rust, stands may be heavily
damaged over limited areas. In those stands,
from 30 to 40 percent of the living and dead
trees will have cankers, and about half the can-
kered trees will have spike-tops (Krebill 1965).
Usually, however, the infection is lighter and
scattered through the stand (Peterson 1962).

Sanitation salvage cutting is about the only
practical way of controlling the disease in forest
stands (Mielke et al. 1968). In areas of high tree
values it may be possible to prune infected
branches from lightly infected trees, but heav-
ily infected trees should be cut. Partial cutting
and thinning appear well adapted to the control
or reduction of Comandra rust, even in heavily
damaged stands, because the disease is not
passed from pine to pine and only the trees
with stem infections need to be removed.

Western gall rust (Peridermium harknessii
Moore) occurs on lodgepole pine throughout the
Rocky Mountains, but is not as distinctive as
Comandra rust because most infections occur
as galls on branches rather than on the trunk.
Mortality in the seedling stage and loss of
growth and cull are the principal forms of dam-
age from this rust. Removal of infected trees in
cultural operations is the only practical way to
control gall rust damage in forests. Presence of
a few galls is not sufficient cause to remove a
tree. Only cankered trees need be cut (Peterson
1960).

The major root and butt fungi attacking
lodgepole pine in the Rocky Mountains are
Polyporus circinatus Fr., Coniophora puteana
(Schum ex. Fr.) Karst, and Armillaria mellea
(Fr.) Quel.; the principal trunk rot fungus is
Forties pini (Fr.) Karst (Hepting 1971, Horni-
brook 1950).

NATURAL REGENERATION
REQUIREMENTS

The basic elements necessary for successful
natural regeneration are the same as for
spruce: (1) an adequate supply of viable seed,
(2) a suitable seedbed, and (3) environmental
conditions compatible with initial survival and
seedling establishment.

Seed Supply

FLOWERING AND FRUITING

Male flowers of lodgepole pine ripen and pol-
len is wind disseminated in late spring and early
summer. Cones from the current year's crop
mature and seed ripens in September and Oc-
tober (Tackle 1961a).

CONE BEARING AGE

Lodgepole pine begins bearing cones with vi-
able seeds at a very young age — in open stands
by trees 5 to 10 years old, in more densely
stocked stands by age 15 to 20 years — and con-
tinues well past maturity (Crossley 1956b,

Table 3 • --Va r i at i ons in serotinous cone habit and estimated average sound seed per acre stored in
serotinous cones on four areas in Montana and Idaho (Lotan 1967a, 1968)

Cone habit

Ave rage

age of stand,
(yrs)

P redomi nate 1 y
se rot i nous

1 n t e rmed i a t e

P redom i na t e 1 y
nonse rot i nous

Average sound seed
stored per acre

Percent of trees ■

Millions

1 1 1

.uneven aged)

1.0

.even aged)

3.2

117

1 .8

191

Tackle 1961a). Seed from trees less than 10
years old can have as high a germination per-
centage as seed from mature trees.

CONE CHARACTERISTICS

The regeneration of lodgepole pine is greatly
affected by its cone habit. Individual trees are
classified as (1) closed cone if 90 percent or
more of the cones are serotinous, (2)
intermediate if less than 90 but more than 10
percent of the cones are serotinous, and (3) open
cone if less than 10 percent of the cones are
serotinous (Crossley 1956b; Lotan 1967a, 1968).

Throughout much of the Rocky Mountains,
the closed cone habit is widespread (Alexander
1966a, Critchfield 1957, Tackle 1961a). In stands
with the serotinous habit, trees bear an abun-
dance of closed cones that remain unopened on
standing trees up to 40 years (Lotan and Jensen
1970). That seed is available for release follow-
ing fire or cutting. In one study over a 10-year
period in central Colorado and southern Wyo-
ming, the average amount of seed stored in
closed cones was 2V2 to 3V2 times greater than
the current crop (Bates 1930). The average
number of sound seeds stored in closed cones
ranged from 181,000 to 1,104,000 per acre.

Although most trees bear either serotinous or
nonserotinous cones, the number of serotinous
cones varies greatly from tree to tree, and the
proportion of closed-cone types varies greatly
between stands (Clements 1910, Mason 1915a,
Lotan 1967a). Lotan (1967a, 1968) studied the
variation in serotinous cone habit and estimated
the number of sound seeds stored in closed
cones on four areas in Montana and Idaho (table
3). Most trees produced almost entirely either
open or closed cones. Only 10 to 20 percent of
the trees were classified as intermediate. The
estimated number of sound seeds stored in
closed cones varied from 0.8 to 3.2 million per
acre.

The fruiting habits of lodgepole pine in Al-
berta suggest a possible relationship of age to
closed cone habit (Crossley 1956b). In young
stands (17 years old) only 17 percent of the trees
had closed cones, while in 55- and 250-year-old
stands, 82 and 83 percent, respectively, of the
trees bore closed cones.

In some areas the cone habit is known to be
nonserotinous. For example, trees in northern
Wyoming on the Bighorn and Shoshone Nation-
al Forests bear largely open cones. Other areas
reporting mainly nonserotinous cones are the
Deschutes Basin and Blue Mountains in Oregon
(Dahms 1963, Mowat 1960, Trappe and Harris
1958).

The variability in closed cone habit means
that each stand must be examined before cut-
ting to determine cone serotiny and estimate the
number of sound seeds available in closed
cones. Lotan and Jensen (1970) have developed
such estimating procedures from data collected
in mature and overmature stands in Idaho and
Montana. They should also provide reasonable
estimates of the number of sound seeds stored
in serotinous cones in similar stands in the cen-
tral Rocky Mountains, however. Seed from non-
serotinous cones can be estimated from conven-
tional seed traps.

TIME OF SEEDFALL

Natural seedfall in lodgepole pine occurs
throughout the year, but not at a uniform rate.
On two study areas in pure, overmature stands
in Montana, only about 20 percent of the yearly
crop shed was released during August and Sep-
tember in 3 out of 4 years; 60 to 70 percent was
shed from October to June the following year,
and the remainder fell in June and July (Boe
1956, Tackle 1964). In the subalpine forest re-
gion of Alberta, maximum annual seedfall
during 3 years of observation in a 60-year-old
stand occurred over a 4- to 5-week period,

and was heaviest the first week in October
(Crossley 1955). In eastern Oregon, most of the
seedfall occurs before November (Dahms 1963,
Mowat 1960).

PRODUCTION AND PERIODICITY

Lodgepole pine has generally been rated a
prolific seed producer, with good crops borne at
1- to 3-year intervals and light crops produced in
the intervening years (Bates 1930, Dahms 1963,
Mason 1915a). On the other hand, Boe (1954)
analyzed cone crop records in Montana, and
rated the 16 crops observed during a 45-year
period west of the Continental Divide as 1 good,
11 fair, and 4 poor. East of the Divide, seed crops
were rated 2 good, 13 fair, and 5 poor for a
20-year period. Part of the apparent differences
in seed production may be in definitions of what
is a good seed year, however.

The number of fully developed seeds per cone
varies widely. In one study on 9 National Forests
in Colorado and Wyoming, cones averaged 26
seeds (Mason 1915a). Cones averaged 40 seeds
in another study of large lots of cones in Col-
orado and southern Wyoming, but individual
cones produced as few as one or two seeds
(Bates 1930). The average number of sound
seeds per cone in Montana and Idaho varied
between 10 and 20 (Lotan 1967a, 1968).

Seed production by individual trees and by
stands also varies considerably. Seeds from old
and new cones together averaged 50,000 per
tree in Idaho and 21,000 per tree in Colorado
(Clements 1910). Annual variations in seed pro-
duction on felled trees during a 10-year period
(1912-21) ranged from 0 to 135,000 per acre in
southern Wyoming, and from 55,000 to 827,000
per acre in central Colorado (Bates 1930). In
central Oregon, where the cones are non-
serotinous and the total crop is released each
year, annual production in uncut stands varied
from 178,000 to 572,000 sound seeds per acre
during a 3-year period (Dahms 1963). In the
other year of the study, only 14,000 seeds per
acre were produced.

In Montana, annual seedfall in stands with
predominately serotinous cones averaged
70,000 sound seeds per acre over a 4-year period
(Boe 1956). Tackle (1964) observed this Mon-
tana area for 2 more years and another area
nearby for 2 years, and reported average annual
release of 65,000 to about 90,000 sound seeds per
acre. In similar stands in Alberta, average an-
nual seedfall varied from 10,000 to 30,000 seeds
per acre during a 3-year period (Crossley 1955).
Most of the seed released in the predominately
serotinous stands probably came from non-

serotinous cones, and represents only a small
proportion of the annual seed production in
these stands.

SEED QUALITY

Variability in seed quality affects sound seed
production. Bates (1930) concluded that the
percentage of sound seed was higher in years of
good seed production than in years of poor pro-
duction. Furthermore, more sound seeds were
available from current cones than from old
cones. On the other hand, a number of studies
have indicated little difference in seed quality
between new cones and those up to 10 years old
(Ackerman 1963, Crossley 1956a, Lotan 1964b).
About 50 percent of the stored seed was viable
in one study (Lotan 1964b). No data are available
for seed from nonserotinous cones.

DISPERSAL

Lodgepole pine seed is light, averaging about
100,000 seeds per pound, with about 1/3 to 1/2
pound of seed per bushel of cones (Bates 1930).
Dispersal from standing trees is largely by
wind, but wind is important only in stands where
nonserotinous cones are abundant (Tackle
1961a). Seedfall into cleared openings has been
studied in Montana and Oregon (Boe 1952, 1956;
Dahms 1963, Tackle 1964). Seed dispersed from
standing timber dropped off sharply at a dis-
tance of about 66 ft and continued to diminish
as distance from the source increased. These
authors concluded that the number of seeds dis-
persed beyond 200 ft from the source was
inadequate to restock a cutover area regardless
of the amount of seed released under the uncut
stand. More seeds were dispersed from the
north and west boundaries than from the south
and east boundaries on most areas studied, but
differences were too small to detect any influ-
ence of prevailing winds on seed dispersal.

In Alberta, Crossley (1955) found a somewhat
different dispersal pattern. Although the
number of seeds falling to the ground di-
minished as distance from standing timber in-
creased, seedfall did not diminish as rapidly in
the first 66 ft, and there was little difference
in the number of seeds falling to the ground
between 66 and 330 ft from standing timber.
He also concluded, however, that the amount of
seed falling into the opening was not adequate to
restock the area.

Seeds released from cones attached to the
slash and cones knocked from the slash and

scattered on the forest floor are the most impor-
tant in regenerating stands with serotinous
cones (Tackle 1961a). Most seeds are released
from this source the first year after exposure
(Boe 1956, Crossley 1956a). Some seeds are re-
leased for as long as 6 years (Tackle 1954b) but
the number is not likely to be significant after
the second year because there is little further
change in cone radiation, height above the
ground, or ventilation (Crossley 1956a). Fur-
thermore, seeds from cones lying on the ground
for as long as 6 years have only about half the
germinative capacity of seeds stored in cones
above the ground for the same period of time
(Tackle 1954b).

Fire is not a requisite for seed release from
closed cones in the slash (Bates et al. 1929), but
heat is necessary. Temperatures of at least 113°
to 122° F are required to melt the resin bond and
allow cone scales to flex and spread apart
(Cameron 1953, Clements 1910). Crossley
(1956a) investigated the effects of solar radia-
tion on cone opening, and found that an air
temperature of at least 80° F at 3.5 ft above the
ground was necessary to provide the heat
needed to rupture the bonds of cone scales.
Furthermore, the cones had to be on or near the
ground surface to open, because at heights
above 7 inches from the ground or other reflect-
ing surface, cone temperatures did not rise suf-
ficiently to melt resin bonds. More cones open
on south slopes than on north slopes, but the
amount of residual overstory apparently has lit-
tle effect on cone opening because only a short
exposure to direct solar radiation is sufficient to
raise temperatures to a critical level (Crossley
1956a, Lotan 1964b).

No data are available from the central Rocky
Mountains on the number of sound seeds re-
quired to produce an established seedling under
different seedbed and environmental condi-
tions. Lotan (1964a, 1968) has suggested that,
under favorable seedbed and environmental
conditions in the northern Rocky Mountains,
30,000 to 50,000 sound seeds per acre are needed
to produce 1,000 first-year seedlings.

In stands with serotinous cones, assuming
that Lotan's figures are reasonable estimates,
the amount of seed stored in closed cones ap-
pears to be more than adequate to insure regen-
eration success if logging slash bearing cones is
carefully handled. In stands with nonserotinous
cones, 30,000 to 50,000 sound seeds per acre are
not likely to be dispersed as far as 200 ft from
standing timber in any one year. This suggests
that the maximum size of opening in a non-
serotinous stand that will restock in a reasona-
ble amount of time is probably no greater than
300 ft wide or about four to five times tree
height.

SOURCE

There are several sources of seed available
for natural reproduction (Tackle 1964). In
clearcut openings, the principal sources are:

1. Serotinous cones in the logging slash (pro-
vides only a one-shot opportunity).

2. Nonserotinous cones on trees standing
around the cleared opening (wind dissemi-
nated about 150 ft).

3. Nonserotinous cones on unmerchantable re-
sidual trees while they are still standing.

4. Nonserotinous cones on new reproduction 5
to 10 years old.

5. Some seed is also available from nonserotin-
ous cones on trees cut on the area.

In partially cut areas, the principal sources of
seed are from serotinous cones in the logging
slash and from nonserotinous cones on residual
trees left on the area. Some seed may also be
available from nonserotinous cones on trees cut
on the area.

One of the significant considerations in clear-
cutting in stands with nonserotinous cones is the
resistance of the seed source to windthrow.
Situations and conditions where windfall risk is
low, moderate, and high have been identified
(Mason 1915a) and recommendations developed
for locating windfirm boundaries on clearcut
units (Alexander 1964, 1967b). These recom-
mendations have been modified to identify the
kinds of trees and residual volumes that can be
successfully retained in partially cut areas for
different windfall risk situations and stand con-
ditions (Alexander 1972).

VIABILITY

The viability of lodgepole pine is rated good.
In a series of 413 uniform tests, an average
germinative capacity of about 80 percent was
obtained after 41 days at 6 to 10 percent mois-
ture with fluctuating diurnal temperatures of
57° to 83° F (Bates 1930). Lodgepole pine will
retain a good germinative capacity for long
periods of time if properly stored. The germina-
tive capacity of seed stored in serotinous cones
is not seriously reduced even after 50 to 75
years (Clements 1910 , Tackle 1954b).
Lodgepole pine seed does not normally require
pretreatment, but stratification may hasten
germination (Tackle 1954b). In nature,
lodgepole pine seed overwinters under the snow
and germinates the following spring.

SEED LOSSES

Lodgepole pine seed crops are subject to loss-
es before seedfall to cone and seed insects
(Keen 1958), but their relative importance, fre-
quency of occurrence, and magnitude are not
known. Pine squirrels consume large amounts
of seed and cones, as evidenced by the large
caches common to lodgepole pine forests. After
seed is shed to overwinter, small mammals such
as mice and chipmunks undoubtedly consume
considerable but unknown amounts of seed. In
western Montana, lodgepole pine seedlings sur-
vived better on protected than on unprotected
spots, but the differences may have been due to
factors other than rodents (Roe and Boe 1952,
Tackle 1961b). In the interior of British Colum-
bia, protection from rodents was essential to
lodgepole regeneration success (Prochnau
1963).

Factors Affecting Germination

Viable seeds of lodgepole pine that survive
overwinter normally germinate in the early
summer following snowmelt in the central
Rockies. Optimum air temperature for germi-
nation is about 70° F (Bates 1930). Air tempera-
tures of 70° F are usually reached in early June
in the central Rocky Mountains, but snow fre-
quently covers the seedbed until middle or late
June. In one study in the northern Rocky Moun-
tains, where seeds were sown in the fall to simu-
late natural seedfall, 90 percent of the germinat-
ing seedlings emerged the first 2 weeks in July
following snowmelt in late June (Lotan 1964a).
Field germination percentages were 74 to 84
percent for all seedbed conditions —
considerably higher than reported for Colo-
rado and Wyoming (Bates 1930).

Lodgepole pine is noted for its ability to ger-
minate on burned surfaces after wildfire. Fire
releases the seed from serotinous cones,
creates a favorable seedbed, and reduces veg-
etative competition for light and moisture.
However, site conditions and intensity of burn,
as well as seed supply, influence germination on
burned seedbeds. Some areas of the same burn
will be overstocked, while other parts will be
poorly stocked or nonstocked (Horton 1953,
1955; Stahelin 1943).

Germination has also been variable on seed-
beds prepared by burning. In Colorado, good
germination occurred in full sunlight on seed-
beds where slash was burned in small piles
(USDA-FS 1943). Good germination occurred on
burned seedbeds in Alberta, but mortality on
the black surfaces was high in full sunlight

(Crossley 1956c). On the other hand, poor ger-
mination has been reported on burned seedbeds
by Ackerman (1957), Boe (1956), and Crossley
(1952). These authors did not indicate, however,
whether poor success was due to high tempera-
tures and surface drying, deep layers of loose
dry ash, or loss of seed supply when cone-
bearing slash was burned. In a greenhouse
study, leached burned soil provided the highest
germination, but unleached burned soil with a
high ash content inhibited germination (Gayle
and Gilgan 1951).

Germination has usually been better on ex-
posed mineral soil and on disturbed duff and
mineral soil than on other seedbed types, pre-
sumably because of more stable moisture con-
ditions (Ackerman 1962, Bates et al. 1929, Boe
1956, Crossley 1956c, Tackle 1964, Trappe
1959). Germination has frequently been good on
the natural forest floor (Boe 1956, Crossley
1956c), but the initial germination is often offset
by heavy mortality when the seedbed dries out
(Ackerman 1962, Prochnau 1963).

The effectiveness of the seedbed is influenced
by any factor that affects temperature and
moisture, as well as depth of slash and distribu-
tion of the slash-borne seed supply.

On clear days in early summer, exposed soil
surfaces are rapidly dried out and heated to
high temperatures. Few seeds can imbibe suffi-
cient water to germinate, and many newly ger-
minated seedlings are killed by stem girdle or
drought. Shade either from light slash or a re-
sidual overstory reduces excessive heating and
drying of the soil surface, thereby improving
germination on both burned and mineral soil
seedbeds (Crossley 1956c, Day and Duffy 1963).
On the other hand, slash may inhibit germina-
tion if it is too deep and a mat of needles and fine
twigs several inches thick accumulates (Boe
1956, Lotan 1964a, Tackle 1954b). Furthermore,
if germination is delayed until late summer
rains, the late-germinating seedlings may not
harden off before the onset of cold weather
(Ronco 1967).

Factors Affecting Initial Survival
and Seedling Establishment

Most lodgepole pine seedling mortality oc-
curs during the first growing season after ger-
mination, but seedlings usually require about 2
to 3 years after germination to become estab-
lished. The first growing season is considered
here to be the period of initial survival, and the
second and third growing seasons as the time of
seedling establishment.

INITIAL ROOT GROWTH

The rate of root growth is an important de-
terminant in the initial survival of lodgepole
pine seedlings. The further the root penetrates
the soil, the better the chance for the seedling to
survive drought and frost heaving. Critical root-
ing depth depends upon the seedbed type,
weather, and soil properties.

There is little information on the first-year
rooting depth of lodgepole pine other than the
growth is slow (Tackle 1961a). Lotan (1964a)
excavated a few seedlings less than 8 weeks old
in the northern Rocky Mountains, and found
roots 5 to 6 inches long on mineral soil seedbeds,
4 inches long on undisturbed duff. Seedlings
initially form a weak taproot but it does not
persist. The initial root system is stunted or
obscured by subsequent lateral root develop-
ment (Horton 1958).

SEEDBED TYPE

In the undisturbed forest, lodgepole pine
seedlings establish most readily in openings on
mineral soil such as upturned mounds resulting
from windfall. Seedlings will become estab-
lished on duff, litter, partially decomposed or-
ganic matter, or decaying wood if they are
under a canopy that provides sufficient light
while preventing the seedbeds from heating and
drying out. Lodgepole pine seedlings do not be-
come established in significant numbers on any
seedbed type under a closed canopy.

The same seedbeds are available after log-
ging and slash disposal, but with some addi-
tional mineral soil, and burned mineral soil and
mineral soil mixed with organic matter. Re-
moval of the overstory modifies the mic-
rohabitat, however, and such factors as organic
seedbeds and competing vegetation frequently
become limiting to natural regeneration suc-
cess. Seedbed preparation to create a more
favorable moisture source can modify limiting
factors sufficiently to enable seedlings to sur-
vive.

Serotinous Cones

In stands with serotinous cones, the effect of
seedbed type on survival and establishment is
frequently confounded with slash disposal
treatments because the seed supply is largely in
the slash-borne cones. Furthermore, natural re-
production with seed from serotinous cones is a
one-shot opportunity, and if the slash is not
carefully handled, good seedbed condi-
tions are wasted.

Lodgepole pine survival and establishment
after logging and slash disposal in the central
Rocky Mountains has generally been best on
prepared mineral soil seedbeds (Alexander
1966a, USDA-FS 1943). In fact, the combination
of dozer piling or windrowing slash for burning,
and mechanically exposing mineral soil has
frequently resulted in so much reproduction
that early thinning is required to control stand
density (Alexander 1966a).

Seedling survival and establishment have
been good on burned seedbeds (Alexander
1966a, 1966b; USDA-FS 1943) except on fully
exposed south slopes or where the seed supply
has been destroyed in slash disposal. In one
study in southern Wyoming, however, seedling
establishment was nearly optimum on seedbeds
where slash was broadcast burned or the con-
centrations burned, and the seed supply in
serotinous cones was largely consumed by the
slash fires. Seed for restocking these small (400
ft wide) openings came from nonserotinous
cones on trees standing around the perimeter
(Alexander 1966a).

Seedling survival and establishment has been
variable on undisturbed seedbeds. On some
areas it was only fair (USDA-FS 1943), but on
other areas, satisfactory numbers and stocking
were obtained on natural seedbeds with only a
light cover of duff and litter. On the latter areas,
slash was either lopped and scattered, or un-
treated slash was less than 1 ft deep and covered
less than 40 percent of the area (Alexander
1966a, 1966b).

In the northern Rocky Mountains and Alberta,
initial survival and establishment were better
on mechanically scarified mineral soil and a
combination of disturbed mineral soil and duff
than other seedbeds (Ackerman 1957, 1962; Boe
1956; Crossley 1952, 1956c; Johnson 1968;
Tackle 1965). In fact, these seedbeds were usu-
ally overstocked. Good establishment was ob-
tained on undisturbed seedbeds on compara-
tively dry sites with a minimum of unincor-
porated organic matter and a paucity of com-
peting vegetation, and on disturbed seedbeds
where slash was lopped and scattered. Satisfac-
tory numbers and stocking of reproduction
were obtained on seedbeds with unburned slash
concentrations and windrows, and where slash
was piled or windrowed and burned. Burning in
general created less favorable seedbeds than
mineral soil unless they were shaded, however,
because of excessive heating and drying.
Furthermore, on burned seedbeds, seedling es-
tablishment was frequently slow during the
first few years after treatment because too
much of the seed supply was destroyed in slash
fires (Boe 1952). Survival and establishment did
not improve until the new reproduction was

large enough to provide a seed source.

On clearcut areas where slash was left un-
treated, seedling survival and establishment
have been better on disturbed mineral soil, dis-
turbed duff, and areas where the depth of slash
was less than 1 ft than on undisturbed duff, un-
disturbed soil, brush and grass, and areas where
the depth of slash was greater than 1 ft (Tackle
1956).

Nonserotinous Cones

Observations of seedling establishment in
stands with nonserotinous cones in northern
Wyoming indicate that regeneration success on
cleared openings within effective seeding dis-
tance has been satisfactory on mechanically
scarified mineral soil and on burned soil seed-
beds where slash was either broadcast burned,
or piled or windrowed and burned. Seedbeds
prepared by rolling and chopping slash have
been about as effective as dozer scarification.
Exceptions have been on south slopes and at
lower elevations, where shade appears neces-
sary to reduce temperatures and conserve
moisture.

CLIMATE

The climate of the lower subalpine and upper
montane where lodgepole pine grows in the cen-
tral Rocky Mountains is warmer and drier than
the higher spruce-fir zone, but the climate is
still characterized by extremes in solar radia-
tion, temperature, and moisture that can limit
regeneration success.

Light and Solar Radiation

Light is essential to lodgepole pine seedling
survival and establishment. Seedlings do not
become established in less than 10 percent full
sunlight, and development is poor in less than 20
percent full sunlight (Clements 1910). Early
seedling development is usually considered
best in full sunlight (Day 1964, Tackle 1961a),
but lower radiation levels may be necessary on
severe sites to reduce mortality (Armit 1966).
Under full exposure, radiation intensities can
create critical temperature and moisture condi-
tions for first-year seedling survival.

In one study on the Fraser Experimental
Forest in Colorado, more than twice as many
seedlings survived the first growing season on
all seedbed types with 60 percent shade than in
either full sunlight or 30 percent shade
(USDA-FS 1943). Similar benefits from over-

head shade have been observed on south slopes,
and at lower-elevation tension zones between
timber and grasslands. On the other hand,
first-year survival of planted lodgepole pine
seedlings was equally good whether shaded or
exposed to full sunlight on some of the most
severe sites in the central Rocky Mountains
(Ronco 1970d). Furthermore, full exposure to
high light intensities did not adversely affect
the rate of photosynthesis. Apparently, full ex-
posure to high radiation intensities is more crit-
ical to newly germinated seedlings than to older
stages.

Temperature

Temperature has been suggested as the least
important of the environmental factors limiting
regeneration success (Clements 1910), but the
characteristic zonal pattern of occurrence of
lodgepole pine in the Rocky Mountains is usu-
ally attributed to temperature at the upper
limits (Tackle 1965).

Bates (1923) rated lodgepole pine as highly
resistant to heat damage, but evidence of heat
injury seems to be conflicting. Temperatures of
125° to 140° F combined with a restricted mois-
ture supply will seriously damage or kill newly
germinated seedlings in the succulent stage,
and heat alone will cause mortality from stem
girdling when temperatures rise to 140° to
160° F (Armit 1966). When air temperature
reaches 80° F in the Rocky Mountains, direct
solar radiation is capable of heating exposed
soil surfaces to these levels (Crossley 1956a,
Day 1964). In Alberta, Ackerman (1957), Cross-
ley (1956c) and Day (1964) indicate that early
shade protection, particularly on burned and
mineral soil seedbeds, would improve survival,
presumably by lowering temperatures and re-
ducing water loss from both seedlings and soil.

In the northern Rocky Mountains, however,
heat girdling of newly germinated seedlings did
not occur as frequently as expected, although
soil surface temperatures commonly exceeded
138° F for several hours and temperatures of
150° to 163° F were observed occasionally on the
surfaces of undisturbed and burned seedbeds
(Lotan 1964a). At the same time, seedlings were
dying from drought. In Colorado, only 2 to 3
percent of the first-year seedling mortality over
a 3-year period was from heat girdling on ex-
posed sites where surface temperatures fre-
quently exceeded 135° F and reached as high as
160° F (Ronco 1967). Soil moisture was suffi-
cient to prevent drought losses.

Frost can occur any month of the growing
season where lodgepole pine grows, especially
in depressions and cleared openings because of

cold air drainage and radiation cooling. Newly
germinated seedlings are especially suscepti-
ble to damage from early fall frosts. In a
laboratory study, first-year seedling suscepti-
bility to frost damage was affected by age as
well as minimum temperature (Cochran and
Berntsen 1973). Seedlings 6 weeks old were
more susceptible to frost damage at night tem-
peratures of 18° F than were seedlings 1 to 4
weeks old. At 2 months of age, all seedlings were
killed by night minimums of 15° F. Previous ex-
posure to near-freezing temperatures reduced
mortality when seedlings were exposed to night
minimums of 20° F or less.

Frost damage after the first year has not been
observed or reported in the central Rocky
Mountains (Ronco 1967).

The combination of warm daytime tempera-
tures, nighttime temperatures below freezing,
and saturated soils unprotected by snow cover
in the early fall are conducive to frost heaving.
In one study in central Colorado, these condi-
tions were observed in 1 out of 3 years, and frost
heaving was the principal cause of first-year
seedling mortality on exposed mineral soil
(Ronco 1967). Seedlings continue to be suscep-
tible to frost heaving after the first growing
season. Shading seedlings reduced mortality by
reducing loss of radiant energy from both seed-
lings and soil.

Moisture

The moisture condition of the seedbed during
the growing season largely determines first-
year seedling survival. In the Rocky Mountains,
summer drought can be a serious threat to
seedling survival and establishment on some
sites. For example, mortality to both natural and
planted seedlings on south slopes in northern
Wyoming has been attributed largely to
drought. In Montana and Idaho, approximately
90 percent of the first-year seedling mortality in
one study was caused by drought (Lotan 1964a).
On the other hand, Ronco (1961b, 1967) ob-
served the survival of newly germinated and
planted seedlings over a period of years, and
concluded that drought was not a serious cause
of mortality in the subalpine of central Col-
orado. However, his studies were at a higher
elevation in the spruce-fir zone where moisture
is generally more abundant.

Precipitation during the growing season is
particularly critical to the survival of seedlings.
Lotan ( 1964a) found that from 50 to 70 percent of
the total mortality in 1 year occurred between
June 22 when germination started and July 13, a
period when precipitation was negligible. Mor-
tality was substantially reduced after more than

1 inch of rain fell beginning on July 13. The
relatively few losses to drought recorded by
Ronco (1961b, 1967) were attributed to frequent
showers after germination began or seedlings
were planted.

Summer precipitation is not always a benefit
to seedling survival and establishment, espe-
cially if storms are so intense that most of the
moisture runs off and soil movement on unpro-
tected soil surfaces either buries the tops or
uncovers the roots of seedlings.

SOIL

Lodgepole pine grows on a wide range of soils
throughout the Rocky Mountains (Johnson and
Cline 1965, Retzer 1962), but little is known
about how soils affect establishment and
growth (Tackle 1965). In general, lodgepole pine
becomes established most readily and makes
best growth on moist, light, well-drained, sandy
or moderately acid gravelly loam soils derived
from granites, shales, sandstones, and coarse-
grained lavas (Tackle 1961a, 1965). It does not
establish readily in the central Rocky Moun-
tains on soils derived from limestone or fine-
grained igneous rocks (Bates 1917a). The
former are too dry, and the latter break down
into clays that are too poorly drained. Lodgepole
pine is generally better able to establish on dry,
rocky soils, on excessively drained light-
textured soils, and severe exposures than are
associated species, but it does not establish
readily on sites with impeded drainage or heav-
ily acid soils.

DISEASES

Newly germinated seedlings are killed by
damping-off fungi. Losses normally occur early
in the growing season before seedlings cast
their seedcoats, and can be serious on all
seedbed types if they remain damp for long
periods of time. In one study, about 14 percent
of the newly germinated lodgepole pine seed-
lings were killed in 2 consecutive years by
damping-off on mineral soil seedbeds (Ronco
1967). Snowmold fungi occasionally damages or
kills both natural and planted lodgepole pine
seedlings. Ronco (1967) found little damage on
pine plantings except during 1 year when
snowmelt was retarded and seedlings remained
under the snow too long. About 20 percent of the
seedlings suffered damage, which was about
equally divided between shaded and open-
grown seedlings.

ANIMAL DAMAGE

Conventional Determination

Ronco (1967) found that mountain pocket
gophers destroyed some planted seedlings each
year, but losses were highest during a popula-
tion peak the third and fourth winters after
planting. Nearly all seedlings destroyed by
gophers were clipped just above the ground
level, but a few died from root destruction
caused by burrowing. Clipping damage to newly
germinated seedlings while the seedcoat is still
attached frequently has been attributed to mice,
but there is no documented evidence of mice
having actually done the damage. A recent
study of clipping damage and mortality to
spruce seedlings on the Fraser Experimental
Forest in Colorado has demonstrated that the
gray-headed junco is responsible (Noble and
Shepperd 1973). It seems likely that juncos or
other seed-eating birds are responsible for simi-
lar damage to lodgepole pine. The mountain
vole, however, will debark and kill established
seedlings.

Young lodgepole pine seedlings are vulnera-
ble to trampling damage from grazing and
browsing animals. In one study of natural re-
production in southern Wyoming (Alexander
1966a), seedbed and slash disposal treatments
created easy travel routes, and cattle fre-
quently were observed to trail through the
study area. While few seedlings were trampled
to death, they were either deformed or damaged
to the extent that they were susceptible to
woodrotting fungi.

The measure of tree growth usually found
most independent of stand factors, and there-
fore the most reliable index of site quality, is the
average height of dominant trees in relation
to age. The relationship of height and age, when
expressed as dominant height in feet at some
specified reference age, is the familiar "site
index" that has come into general use as the
conventional measure of site quality.

The height growth of most conifers is inde-
pendent of stand density over a wide range of
stocking. The family of site-index curves de-
veloped for those species simply expresses the
relationship between height growth and the in-
dependent variables of site quality and age. The
rate of height growth of lodgepole pine, how-
ever, is influenced by stand density probably
more than any other North American conifer
(Holmes and Tackle 1962, Smithers 1956). For
lodgepole pine, therefore, a third variable
— stand density — must be considered.

Curves and tables of the height, age, and den-
sity relationships of dominant lodgepole pine
(Alexander 1966c, Alexander et al. 1967) are
suitable for estimating site index at base age 100
years where total age is at least 30 years and
density ranges from CCF (Crown Competition
Factor) 125 or less to CCF 500 (Krajicek et al.
1961) (fig. 25). Data for these curves came from
the stem analyses of 1,048 dominant lodgepole
pines on 262 plots in the western United States,
sampled to represent a wide range of age, site
quality, and density.16

GROUND VEGETATION

Most studies of lodgepole pine regeneration
have indicated that competing vegetation is a
major constraint to successful establishment
(Ackerman 1962, Boe 1956, Crossley 1956c,
Lotan and Dahlgreen 1971, Tackle 1964). No
benefits from understory vegetation of the kind
that would provide protection for newly germi-
nated seedlings has been reported.

SITE QUALITY

Site quality is commonly used to express the
productive capacity of different forest envi-
ronments. Determination of productivity is
basic to the prediction of yields, the establish-
ment of optimum levels of growing stock, and
consequently, the level of management that can
be profitably applied to any area.

^Equations and computer subroutines for estimating
site quality have been developed by Brickell (1970) from
these curves, but the base age was changed to 50 years.

20 40 60 80 100 120 140 160 180 200
Total age (years)

Figure 25.— Site index curves for lodgepole pine at CCF
levels of 125 or less. Base age: 100 years total age.

When these site index curves or tables are
used, the steps below should be followed (de-
tailed procedures are outlined by Alexander
1966c):

1. Determine average height and age of the
stand. Select four or more dominants (site
trees) and measure heights and ages in the
conventional manner. Average total age may
be approximated by adding 9 years to the
average age at breast height.

2. Determine the density of the stand in which
the "site trees" developed, either by estimat-
ing CCF from (1) measurements of stand
diameters or (2) measurements of basal area
and average stand diameter.

3. Determine site index from the appropriate
curves or tables, based on the average height
and age determined in step 1 and the CCF
determined in step 2.

Trees — in addition to being dominants — and
stands should meet the following specifications:

Stands

1. Even-aged — not more than 20 years spread
in the age of dominant trees.

2. At least 30 years old, but not more than 200
years old (at least 50 years old in Pacific
Northwest).

3. Apparent site the same throughout the stand.
Site will be considered the same if all trees
are growing on similar topography, slope,
aspect, and soils.

Site Trees

1. Located in an area in the stand where present
density is uniform, and there have been no
abrupt changes in past density.

2. Increment cores show a normal pattern of
ring widths from pith to cambium.

3. Reasonably free of dwarf mistletoe or other
diseases or injuries that may reduce height
growth.

4. Sound enough for ring counts.

5. Show no visible evidence of crown damage,
or tops that are broken, forked, and so forth.

Determination from Soil and Topography

Conventional methods of site determination
cannot be used on lands that are nonforested or
contain trees either too young or unsuitable for
site determination. An alternative approach is
to evaluate environmental factors that influ-
ence site productivity, and combine these into a
predictive equation.

Site index of lodgepole pine in north-central
Colorado and south-central Wyoming can be es-
timated from environmental factors using pro-
cedures developed by Mogren and Dolph (1972).
Data came from 72 plots in pure, even-aged (70-
to 150-year-old) stands on the Medicine Bow,
Roosevelt, and Arapaho National Forests. The
prediction equation is:

Y = 64.99 - 0.345X1 to .339X2 - 0.458X,

_f 0.436X4

Where

Y = site index in feet,

Xj = percent by w ight of particles larger
than 0.25 mm in diameter in the A horizon,

X2 = total soil depth to the C horizon in inches,

Xg = estimate of surface stoniness in percent,
and

X^ = average annual precipitation in inches.
Sy.x = ± 8.0 ft, R2 = 0.78

Estimates of site index from these environ-
mental factors apply only to the point sampled,
but in practice site index sampled from what
appears to be the extremes on the ground for
any given area is usually all that is needed.

Site indexes for lodgepole pine from en-
vironmental factors have not been developed
for other areas in the central Rocky Mountains.

Productivity indexes for lodgepole pine based
on vegetation, soils, or landform, or a combina-
tion of these factors have been developed in
Canada and the Pacific Northwest by Duffy
(1964), Illingworth and Arlidge (1960), Stanek
(1966), Youngberg and Dahms (1970) and
others, but productivity in relation to these fac-
tors has not been investigated in the central
Rocky Mountains.

GROWTH AND YIELD

Forest management in the lodgepole pine type
in the central Rocky Mountains is in a period of
transition from unmanaged to managed stands.
Management is based on silvicultural control
over (1) growth and development of individual
trees and (2) growth and yield of stands for dif-
ferent products. The most powerful silvicul-
tural control available to the manager is the
manipulation of the amount and distribution of
growing stock by thinnings and other inter-
mediate cuttings.

Growth of Immature Stands
NUMBER OF STEMS

Lodgepole pine often reproduces so abun-
dantly following fire or clearcutting that com-
petition for growing space does not permit good
development (fig. 26). Although shade-
intolerant, lodgepole pine does not thin well
naturally, and severe crowding of young trees
of the same size leads to stagnation of growth. In
Colorado, for example, 10 small plots estab-
lished in a young stand after fire supported an
average of 44,000 trees per acre (Mason 1915a).
In Montana on burned areas, there were as
many as 300,000 1-year-old seedlings per acre,
and up to 175,000 8-year-old trees per acre
(Tackle 1961a). Initial stocking largely governs
reduction in number of stems per acre in
natural stands as development progresses. In
one study, very heavy mortality (10,200 stems
per acre) occurred in a 35-year-old stand over a
20-year period (Alexander 1960). Even with
fewer stems per acre and crown classes well
differentiated, however, too many trees persist
to make good use of available growing space,
and artificial thinning is needed to concentrate
growth on fewer stems.

Lodgepole pine stands are also characterized
by extreme variation in number of trees per

acre. Variations in stocking are associated more
with such factors as differences in fire intensity
and seedbed condition, previous age and stand
density, and available seed supply than with site
quality (Smithers 1961). Dense stands remain
dense regardless of site quality.

Thinning generally reduces mortality in
proportion to the number of stems removed
(Alexander 1960, 1965; Barrett 1961). Mortality
in thinned stands is little affected by age or
initial size.

DIAMETER

Because of its response to changes in stand
density, diameter growth is usually used in
thinning studies to measure release. Diameter
growth of lodgepole pine is usually considered
slow, but slow growth is due largely to over-
crowding.

Most thinning studies show that diameter
growth is greatest at the lowest density and
slowest at the highest density (Alexander 1956b,
1960, 1965; Barrett 1961; Dahms 1967, 1971a,
1971b; Smithers 1957, 1961). This relationship
holds whether all trees or the largest 100, 200,
300, and so forth, trees per acre are compared.
In contrast, Daniel and Barnes (1959) reported
that, when stand density was 2,500 stems per

Figure 26.— Dense 60-year-old stand of second-growth lodgepole pine. Medicine Bow

National Forest, Wyoming.

acre or less, the diameter growth of the 400
largest trees per acre was only moderately im-
proved by heavy thinning. Furthermore, aver-
age diameter of the 400 largest trees decreased
more rapidly than for all trees as stand density
increased above 2,500 stems per acre.

In central Oregon, diameter growth was
poorly correlated with initial diameter (Dahms
1971a, 1971b). Alexander (1960) found, how-
ever, that for comparable stand density in the
central Rocky Mountains, the larger the initial
diameter the larger the average stand diameter
at any periodic interval after thinning. He also
found in an earlier study (Alexander 1958c) that
average diameter growth per tree in stands 30
to 80 years old was greater in younger than
older stands at any stocking level from 200 to
20,000 stems per acre (fig. 27). In all stands
examined over long periods of time, there was a
tendency for diameter growth to slow with in-
creasing age (Alexander 1960, Dahms 1971b).

The effects of stand density on diameter
growth are well documented, but there is little
information on the effect of site quality on
diameter growth. Smithers (1957) suggested
that the diameter growth of the 200 largest trees
per acre was more rapid on good than poor sites
in stands of comparable density over a range of
ages. Myers' (1966) yield tables for managed
stands indicate a similar relationship between
diameter growth and site quality.

HEIGHT

in thinned than unthinned stands, in others the
reverse was true, and in still others there were
no differences. In central Oregon, the height
growth of all trees and 100 largest trees per acre
was increased by reducing stand density, but
the differences between levels of stocking were
slight (Barrett 1961, Dahms 1967, 1971b). In
Montana, the height growth of dominant and
codominant trees was greater than for inter-
mediate and suppressed trees within treat-
ments, but there was no difference in height
growth between treatments for comparable
crown classes (Lotan 1967b).

In unthinned stands, the effect of stand den-
sity on height growth has been well documented
(Holmes and Tackle 1962, Smithers 1956, 1957).
For that reason the dominant height of
lodgepole pine does not constitute a valid site
index unless it is adjusted for any reduction due
to stand density (Alexander 1966c, Alexander et
al. 1967). The changes in dominant height of
lodgepole pine with age and site quality are
shown in figure 25 for the range of stand
density — measured as CCF — where height
growth is unaffected. At age 50 years, for ex-
ample, dominant height varies from 20 to 64 ft in
response to variations in site quality. At CCF
300, the dominant height of trees in a
50-year-old stand varies from 16 to 50 ft (Alex-
ander 1966c). Here the response to changes in
site quality are confounded by stand density.
Without the adjustment in site index, the esti-
mate of site quality would not be valid.

The response of height growth to thinning has
been variable. In Colorado and Wyoming, no
consistent relationship was found between the
height growth of either all trees or the 100
largest trees per acre and age, average stand
diameter, or stand density (Alexander 1960,
1965). On some plots, height growth was greater

30yrs

.16

.14

40yrs

% 12

50yrs

-.10

60yrs

70 yrs

§08

80yrs

.04

.02

200

500

1,000 5,000 10,000 20,000

Stems (per acre)

Figure 27. — Relationship of average annual diameter
growth per tree to age and number of stems per acre.

BASAL AREA

Most thinning studies have shown that total
basal area growth per acre is related to stand
density. The greater the initial basal area or
number of stems the greater the basal area at
any periodic interval (Alexander 1960, 1965;
Dahms 1971a, 1971b). These studies also show
that basal area increment per acre decreases
with increasing age, but there is less agreement
on the rate of basal area increment in relation to
stand density. In a study in the central Rocky
Mountains, basal area increment in stands av-
eraging 1 inch in diameter increased with an
increase in number of stems up to 1,200 per
acre, while in stands where the average d.b.h.
was 5 inches, basal area increment decreased
when the number of stems per acre increased
above 300 or when basal area per acre was about
80 ft2 (Alexander 1960). In another study on the
Fraser Experimental Forest in Colorado, there
were no differences in basal area increment be-
tween thinned and unthinned stands despite
drastic reductions in stand density (Alexander
1956b, 1965). Elsewhere, Barrett (1961), Dahms

(1971a, 1971b), and Daniel and Barnes (1959)
reported that basal area increment increased
with an increase in basal area per acre.

VOLUME

Volume per acre is the ultimate objective of
yield prediction; in young stands ft3 volume is of
most interest. Thinning studies in Colorado
show that total ft3 volume per acre increases
with an increase in stand density (Alexander
1965), but in Oregon and Alberta, an increase in
the number of stems reduced total ft3 volume in
densely stocked stands (Dahms 1971b, Smithers
1956). There is also disagreement on the rela-
tionship of total ft3 volume increment to stand
density. In some studies, thinning resulted in a
temporary reduction in total ft3 volume incre-
ment (Alexander 1965, Dahms 1971a). Thereaf-
ter, total ft3 increments of thinned and un-
thinned stands were comparable. In other
studies, total ft3 volume increment increased
with an increase in stand density measured as
either basal area or CCF (Dahms 1966, 1967). In
most studies, however, net total ft3 volume was
greater in thinned than unthinned stands except
at very low densities. Furthermore, regardless
of whether thinning increased total ft3 volume
increment, growth on thinned plots was concen-
trated on fewer, larger, and more usable stems
(Alexander 1965; Dahms 1967, 1971b).

Crown Size

Under stand conditions, the crowns of
lodgepole pine tend to be conical. The relation-
ship of crown size to individual tree growth has
been determined for open-grown trees in the
Rocky Mountains (Alexander et al. 1967). Fig-
ure 28 shows the relationship of the crown width
of open-grown pines to diameter at breast
height for the central Rocky Mountains, Inter-
mountain area, Pacific Northwest, and the three
areas combined. Dahms (1971b) investigated
the effect of stand density on crown length and
width in thinned young stands. He found that 10
years after thinning, crowns were wider and
longer for trees of comparable diameters at the
lowest stand densities observed.

Volume Tables

Volume tables and point sampling factors
have been prepared for lodgepole pine in Col-
orado (Myers 1964, 1969). These tables include:

1. Gross volumes in total and merchantable ft3.

2. Gross volumes in fbm, both Scribner and In-
ternational Vi-inch log rules.

3. Point sampling factors for merchantable ft3
and fbm.

Volume per unit of area may be determined
from either:

1. Measurements of tree diameters and
heights,

2. Measurements of diameters and sufficient
heights to convert tables to local volume ta-
bles, or

3. Tree counts obtained by point sampling.

Yields of Unmanaged Old-Growth Stands

Although the proportion of lodgepole pine
stands still in old-growth is not as high as in

RM data

INT data

PNW data

All data

J l I I L

i i i i i I l

2 6 10 14 18 22 26
Diameter (inches)

Figure 28. — Relationship of crown width to stem diameter
at breast height for open-grown lodgepole pines. (RM =
Rocky Mountain; INT = Intermountain; PNW = Pacific
Northwest.)

spruce-fir forests, many of the poletimber-sized
stands are also overmature. The manager,
therefore, must largely accept what nature has
provided during the period of conversion to
managed stands. Forest Survey data indicate
that average annual growth over all sites in
old-growth lodgepole pine is about 25 to 40 fbm
per acre. This low productivity is largely due to
the great number of small trees.

Average volumes per acre in unmanaged
old-growth stands in the Rocky Mountains de-
pend on both density and environment. For ex-
ample, in a 100-year-old stand, maximum vol-
ume was 20,000 fbm with 800 stems per acre,
and only 1,500 fbm with 1,800 stems per acre
(Tackle 1961a). In Colorado and Wyoming,
yields of 12,000 to 15,000 fbm per acre are gen-
erally considered good; yields of 20,000 to
25,000 fbm per acre are exceptional (Thompson
1929).

Thinning studies have shown that, by reduc-
ing stand density at a young age, it is possible to
obtain production comparable to ponderosa
pine in the Black Hills — net annual increment
of 150 fbm per acre on average sites — and dis-
tribute this growth over fewer and larger stems.

Yields of Managed Stands

Old-growth lodgepole pine sawtimber- and
poletimber-sized stands are being converted
into stands that must be managed from the re-
generation period to final harvest. Further-
more, there are many stands of young growth
that must be brought under management. Some
of these stands have been thinned once but are
in need of a second thinning.

Yield tables for managed stands are the basis
for timber management planning. They report
probable wood yields that will result from
specified combinations of such factors as site
quality, utilization standards, and frequency
and intensity of thinning. They also provide an
important part of the information needed for
determining the influence of timber treatments
on all forest resources. Yield tables for
lodgepole pine are useful regardless of the cur-
rent level of management. Well-managed
forests can benefit from refinements in opera-
tions that are guided by comparisons of actual
conditions with a good standard. Where conver-
sion to managed stands is underway, yield ta-
bles provide goals toward which conversion can
be directed. Furthermore, a manager should not
be restricted to only one yield table per working
group or series of stands managed under the
same silvicultural system. He must have the
opportunity to examine the probable results of

his operations, to make necessary changes in
the management of any of his resources, and to
study the effects of these changes before money
is spent on them (Myers 1967).

Field and computer procedures for preparing
yield tables for managed stands, including those
infected with dwarf mistletoe, realistically
simulate (1) stand growth, (2) response to thin-
ning, and (3) reproduction cutting by any of the
even-aged systems (Myers, 1967, 1971; Myers et
al. 1971). These procedures were developed
from field data on past growth in relation to
stand density, age, and site quality obtained
from a large number of temporary plots in exist-
ing thinned stands of lodgepole pine.

To use the procedures in stands ready for
final harvest and conversion to managed stands,
the manager must decide on (1) the regenera-
tion system — clearcutting, group selection or
shelterwood — with natural or artificial regen-
eration, (2) the site index, (3) initial stocking
(between 1,500 and 2,000 stems per acre at age
10 years are recommended because lodgepole
pine requires some crowding at early ages to
obtain height growth) and (4) age of initial thin-
ning. He can then use the computer simulation
program to produce a series of yield tables for
different combinations of growing stock levels,
cutting cycles, and rotation ages that will show
how project outcomes will vary in response to
different cultural treatments. The manager can
then examine the probable results of different
courses of action, and select the one that best
meets his particular management goals.

To use the procedures to put existing stands
not yet ready for final harvest under manage-
ment, the manager must develop the necessary
working tools from information obtained on
age, diameter, height, site quality, stand den-
sity, and past growth. He can then use the
computer simulation program to produce a
series of yield tables for different combinations
of growing stock levels, cutting cycles, and ro-
tation ages that will show how project outcomes
will vary with intermediate cutting treatments
and past site and stand conditions. The manager
can then select the one that best meets his man-
agement goals.

Cole (1971) has developed a stand volume
equation for even-aged stands of lodgepole pine
in Montana and Idaho that gives direct esti-
mates of gross total ft3 volumes from measure-
ments of stand basal area and the height of
dominant trees, and provides conversion fac-
tors to estimate merchantable ft3 volumes. This
equation should be substituted when Myers'
(1967, 1971) computer simulation program is
used to estimate yields of managed stands of
lodgepole pine in the northern Rocky Moun-
tains.

SILVICULTURE AND MANAGEMENT OF
OLD GROWTH

Regeneration Silviculture

Harvest-cutting methods applicable to old-
growth lodgepole pine forests include clearcut-
ting, and shelterwood and group selection cuts.
Seed-tree and individual-tree selection cutting
are usually not applicable. The objective of each
regeneration system is to harvest the timber
crop and obtain adequate reproduction. The
choice of cutting method in lodgepole pine
stands depends upon management goals, but
stand conditions, windfall, disease and insect
susceptibility, and the risk of potential fire
damage that vary from place to place on any
area limit the options available for handling in-
dividual stands. Furthermore, the economics of
harvesting, manufacturing, and marketing
wood products from a large number of small
diameter trees in the central Rocky Mountains
further limits cutting practices. Cutting to
bring old-growth lodgepole pine under man-
agement is likely to be a compromise between
what is desirable and what is possible. Man-
agement on many areas may involve a combina-
tion of clearcutting small areas, several partial
cutting treatments, and no cutting.

CLEARCUT AREAS

Clearcutting is a regeneration system that
harvests the timber crop in one step. Forest
managers concerned with timber production
have most often elected to convert lodgepole
pine to managed stands by clearcutting in
strips, patches, or blocks. There are several
reasons for this: (1) Lodgepole pine, a pioneer
species, is shade-intolerant and reproduces best
in most instances when overstory competition
is removed or drastically reduced. (2) Dwarf
mistletoe — present in many stands in varying
degrees — is best controlled by separating the
old stand from the new. (3) Windfall and moun-
tain pine beetles, while variable, are always a
threat. (4) The potential for future growth is
limited because of the generally low vigor of
mature and overmature stands and the sup-
pressed condition of many smaller trees. Fur-
thermore, many natural stands appear to be
even-aged, having developed after catastrophic
fires or other disturbances.

Harvesting and regeneration practices de-
veloped in the Rocky Mountains have been di-
rected toward clearcutting. Much of the criti-
cism directed at clearcutting in general has
been associated with concern about (1) the large
openings cut, (2) geometric patterns that did not

complement the landscape, (3) logging slash
and unmerchantable debris left on the ground,
(4) failure of areas to regenerate, and (5) the
unknown effect of roadbuilding and logging on
other forest resources. In some cases the objec-
tions are valid, but with some critics, clearcut-
ting has unjustifiably become synonymous with
devastation.17

From a silvicultural point of view, clearcut-
ting is still an acceptable harvesting method in
lodgepole pine where timber production is a
major objective, providing the knowledge a-
vailable is put into practice. Under some condi-
tions clearcutting is the only alternative to no
cutting. Furthermore, a combination of cleared
openings and high forest is desirable for in-
creasing water yields and improving wildlife
habitat. The following section will therefore
consider the practices needed to regenerate
clearcut areas with natural or artificial regen-
eration.

Management with Advanced Regeneration

There is seldom a manageable stand of ad-
vanced regeneration under pure lodgepole pine,
or if present it has been suppressed for so long
that it has no future management potential. In
mixed stands, where the associated species are
spruce and fir, there is frequently a stand of
advanced reproduction. Procedures developed
for spruce-fir stands should be followed to (1)
evaluate the potential for management before
logging, (2) set up cutting and slash disposal
controls necessary to save the advanced repro-
duction if the manager decides to use it, and (3)
evaluate the adequacy of stocking and need for
fill-in reproduction after logging (Roe et al.
1970).

Management with Reproduction
Following Cutting

Most lodgepole pine areas will be regenerated
with either natural or artificial reproduction
after logging. Cutting unit layout, logging plans,
and slash disposal and seedbed treatment
should be designed to (1) facilitate seed disper?
sal, (2) promote seedling survival and estab-
lishment, and (3) create favorable growing con-
ditions. If natural regeneration fails, plans
should be made to use artificial regeneration.

xlLotan, James E. The clearcutting controversy and
management of lodgepole pine. (Manuscript in prepara-
tion at Intermt. For. and Range Exp. Stn., Ogden, Utah.)

Clearcutting can be by patches, blocks, or
strips. Those cutting practices can be readily
adapted to multiple-use land management by
judicious selection of size, shape, and arrange-
ment of openings in combinations with other
high-forest cutting practices.

Size of Opening. — Successful natural regen-
eration in lodgepole pine depends upon an ade-
quate supply of seed falling on a receptive
seedbed. In the central Rocky Mountains there
are no data on seed-to-seedling ratios, but Lotan
(1964a) estimated that from 30 to 50 sound seeds
would be required to produce one first-year
seedling on mineral soil seedbeds with abun-
dant moisture and favorable temperatures. As-
suming that an arbitrary minimum of 1,500
first-year seedlings are sufficient to allow for
normal mortality and still provide the density
necessary to obtain early height growth, be-
tween 45,000 and 75,000 sound seeds per acre
will be needed before the seed supply can be
considered adequate.

The size of opening that is likely to receive
sufficient seed to restock receptive seedbeds is
influenced by whether the seed is dispersed by
open or closed cones. The manager cannot as-
sume that the cone habit is either serotinous or
nonserotinous. He must examine each area and
classify the stand as (1) closed cone, (2) open
cone, or (3) intermediate. If the stand is clas-
sified as closed cone, the manager must then
determine if he has sufficient sound seed stored
in closed cones to provide an adequate seed
source for natural regeneration, using the pro-
cedures developed by Lotan and Jensen (1970).

1. Stands with Serotinous Cone Habit. — The
size and shape of openings cut in these stands
that will restock is highly flexible if there is
an adequate supply of seed. Natural regen-
eration is a one-shot opportunity, however,
because the seed supply is in the slash-borne
cones. There is no advantage to cutting open-
ings larger than 30 to 40 acres, even for
dwarf mistletoe control,' 7 and openings 10 to
20 acres would be more compatible with
other uses. On south slopes and other dif-
ficult regeneration chances, it may be desir-
able to cut openings smaller than 10 acres to
provide a supplemental seed source in trees
standing around the perimeter. If there is not
an adequate supply of seed in closed cones,
follow the recommendations below.

2. Stands with Nonserotinous or Intermediate
Cone Habit. — The cutting unit must be de-
signed so that seed from the surrounding
timber margin reaches all parts of the open-
ing unless artificial regeneration is planned.

Effective seed dispersal distance from
standing trees has not been studied in the
central Rocky Mountains, but studies else-
where (Boe 1956, Dahms 1963, Tackle 1964)
indicate that, with favorable seedbed and
environmental conditions, the effective
seeding distance in lodgepole pine is about
150 ft. The maximum width of opening likely
to restock to natural reproduction is there-
fore 300 ft, or about four to five times tree
height. Furthermore, it is not likely that suf-
ficient seedfall to provide adequate stocking
will be obtained from only one seed crop. On
south slopes openings should be
smaller — 150 ft wide or about two to three
times tree height. If larger openings are cut,
plan on planting the area beyond effective
seeding distance.

Windfall. — Windfirmness must be a signifi-
cant consideration in the location of cutting
boundaries, especially in stands with non-
serotinous cones. Guidelines for minimizing
windfall around the perimeters of clearcut
openings in spruce-fir forests (Alexander 1964,
1967b) should also be used when locating boun-
daries for lodgepole pine clearcuts.

Seedbed Preparation and Slash Dis-
posal.— There are a number of things to con-
sider in planning the treatment of lodgepole
pine slash: (1) in stands with serotinous cones,
careful handling of slash is required to avoid
destruction of seed-bearing cones, (2) heavy
concentrations of slash obstruct seedling estab-
lishment and are a fire hazard, and (3) slash
creates an adverse visual impact.

1. Stands with Serotinous Cone Habit. — Dozer
piling or windrowing dry slash over the en-
tire area has usually resulted in overly dense
stands of reproduction because abundant
seed is shaken out of cones onto exposed
mineral soil seedbeds (Alexander 1966a, Boe
1956, Tackle 1964). Dozer piling and wind-
rowing slash, then burning the concen-
trated slash, has frequently resulted in poor
stocking, especially when the slash fires
burned over much of the area and destroyed
most of the seed. Broadcast burning usually
results in little or no restocking because
most of the seed is destroyed. Disposal of
slash by lopping and scattering, and by roll-
ing and chopping have resulted in adequate
restocking if sufficient mineral soil (about
40 percent of the area) has been exposed and
the seed-bearing cones are placed near the
ground. Fire hazards and visual impact are
usually not reduced sufficiently, however.

Concentrations of slash must be treated.
If these concentrations are piled or wind-
rowed for burning, the piles and windrows
must be kept small (1/20 acre or less) and
well distributed so that the burned area does
not occupy more than 25 percent of the total
area. The lighter areas of slash — less than
40 percent of the area covered with slash less
than 1 ft deep — can be either lopped and
scattered or rolled and chopped. This combi-
nation of treatments will reduce fire hazards
and visual impact, provide exposed mineral
soil, scatter the cone-bearing slash over the
area, and place the cones near or on the
ground.

2. Stands with Nonserotinous or Intermediate
Cone Habit. — Slash can be handled in the
same way as in stands with serotinous cones,
or it can be broadcast burned. If slash is piled
or windrowed for burning, the piles should
be kept small and well distributed because
burning in large concentrations often heats
the soil enough to inhibit subsequent plant
growth. To be effective, broadcast burning
should cover about 75 percent of the area. It
should consume most, but not necessarily all,
of the logging slash, other debris, and duff or
organic material on the ground, and it should
burn hot enough to destroy most of the com-
peting vegetation. It should not burn so hot,
however, that a deep layer of loose ash ac-
cumulates. Areas with light slash can be
lopped and scattered or rolled and chopped.
It may be necessary to do some additional
mechanical scarification on lopped and scat-
tered areas. Tractors with brush blades
should be used, and about 40 percent of the
area should be left with exposed mineral soil.

Management for Artificial Regeneration

Planting. — Guidelines for planting lodgepole
pine are not available in the central Rocky
Mountains, but many of the recommendations
for spruce planting prepared by Ronco (1972)
are applicable to lodgepole pine.

1. Need and Timing. — Sites scheduled for
planting should be reforested immediately
after logging and slash disposal. Areas pre-
pared for natural reproduction that fail to
restock in 3 years should be planted, other-
wise additional seedbed preparation is likely
to be needed. A minimum goal should be
1,200 well-established seedlings per acre
where timber production is a primary objec-
tive. If the manager intends only to hold the

site, a minimum of 600 seedlings per acre is
sufficient.

2. Site Preparation. — Planting will ordinarily
require just as much seedbed preparation as
natural seeding. Exceptions are areas where
slash has been broadcast burned or com-
pletely cleaned up by dozer piling or wind-
rowing and burning within 3 years of plant-
ing. However, burned areas with deep layers
of loose ash will require ground preparation.
Hand site preparation will probably be ade-
quate on small planting jobs and for fill-in
planting. Hand-scalped spots should not be
smaller than about 18 to 24 inches square.
Aboveground parts of competing vegetation
should be totally removed. On large areas, or
where hand scalping is unsatisfactory be-
cause of dense grass or herbaceous vegeta-
tion, mechanical site preparation should be
used. Machine methods include disking,
plowing (furrowing, mounding, and ridging),
and dozing. Complete scarification is not
necessary, but vegetation-free areas should
be about 2 ft wide and lie on the contour.
Where competing vegetation consists of
brush, tractors equipped with angle dozer
blades should be used to either completely
clear the area or remove the brush in strips
the width of the dozer blade.

3. Planting Stock. — Plant only stock that meets
the following specifications: (1) stem
caliper, Vs inch, (2) tops no shorter than 3
inches, (3) roots at least 9 inches long, and (4)
top- root ratio no more than 3 to 1.

4. Planting Season. — Lodgepole pine should be
planted in the spring after snowmelt. Plant-
ing should be completed by June 25. Tem-
porarily suspend planting during the regular
season when temperatures are unseasonably
warm, especially on clear days when the
wind is blowing.

5. Storage. — Lodgepole pine planting stock
must be lifted while seedlings are still dor-
mant, and stored at the nursery until the
planting sites are free of snow. Storage
should not be extended for longer than 3
months. During transit from nursery to
planting site, the seedlings must be treated
as dormant plants. If refrigerated transport
is not available, the bundles or bags should
be covered with canvas to protect them from
the sun and wind. Temperatures should be
maintained between 34c and 40c F. Packages
should be arranged to provide air circulation
under the covering. Water trees in bundles
before loading. Storage problems are more

severe in the field because limited facilities
on the planting site make temperature con-
trol difficult. Well-insulated storage sheds
that can be cooled by ice or snow can be used
in the absence of mechanical refrigeration.
Trees in bundles should be kept moist and
care taken not to lower temperatures below
freezing. If storage sheds are not available,
cool, moist cellars or snowbanks can be used.
Seedlings can be held in local storage up to 7
days if temperatures can be maintained
below 40° F. Otherwise, local storage should
be limited to 3 days. When transferring trees
from bundles or bags to planting containers,
handle the seedlings carefully to prevent
breakage and keep the roots covered with
moist spaghnum moss.

6. Spot Selection. — Plant seedlings in moist
mineral soil. On areas that have been hand
scalped, seedlings should be planted to take
advantage of dead shade wherever possible.
The north and east side of stumps, logs, and
rocks are favorable locations. Avoid planting
in deep layers of loose ash, adjacent to
shrubs or other live vegetation that com-
petes for soil moisture, near cut banks and
under logs where sloughing action can injure
or kill seedlings, and trails or stock concen-
tration areas where trampling damage may
occur. Choice of planting spot is less critical
on areas that have been plowed or stripped;
there is little opportunity for individual spot
selection when using tree-planting
machines.

7. Planting Method. — Use the hole method for
hand planting. Dig holes with mattock hand
tools or power augers. If augers are used, do
not dig holes too far in advance of planting or
they will dry out.

8. Plantation Protection. — New plantations
should be protected from trampling damage
by livestock until seedlings are at least 3 ft
high. This will require fencing or other ad-
justments in grazing allotments. New plant-
ings should also be protected from rodents.
Sample the rodent population on the areas to
be planted. If populations are large, provide
controls until seedlings become established.

9. Records. — Adequate data from detailed rec-
ords are needed to (1) correct deficiencies
causing failure, and (2) recognize good prac-
tices leading to successful plantations. Deci-
sions affecting regeneration practices can
then be based on quantitative information

rather than conjecture. Follow the recom-
mendations suggested by Ronco (1972).

Seeding. — Techniques have not been worked
out in the central Rocky Mountains, but direct
seeding of lodgepole pine on prepared seed
spots has been successful in the northern Rocky
Mountain and Intermountain regions. In a study
in an Abies lasiocarpa-Vaccinium scoparium
habitat type in northwestern Wyoming, 12 seeds
(90 percent viable) were sown in June on hand-
prepared seed spots and covered with Vs inch of
soil (Lotan and Dahlgreen 1971). Rodents were
controlled by poison baits. After 3 years, viable
seed-to-seedling ratios were 5:1 on scalped
12-inch-square spots on the level and along the
slope; 12:1 on scalped 5-inch-square spots along
the slope; and 60:1 for seed sown in the ash and
duff left by broadcast burning of logging slash.
The percentages of stocked spots were: 72 per-
cent for scalped 12-inch squares on the level; 64
percent for scalped 12-inch squares on the
slope; 38 percent for scalped 5-inch squares;
and only 10 percent for ash-duff seedbeds.

Roe and Boe (1952) and Tackle (1961b) also
successfully spot seeded lodgepole pine on
scalped 6- to 12-inch areas in central Montana.
Seed-to-seedling ratios were about 5:1 for
10-year-old seedlings.

Spot seeding usually results in better success
than broadcast seeding because the seed is
placed in a more favorable environment and
covered with soil (Lotan and Dahlgreen 1971).

PARTIAL CUT AREAS

Shelterwood and group-selection cutting and
their modifications can be used in old-growth
lodgepole pine. These regeneration systems
harvest the timber on an area in more than one
step. From a silvicultural point of view they are
the only acceptable options open to the manager
where (1) multiple-use considerations preclude
clearcutting, (2) combinations of cleared open-
ings and high forest are required to meet the
needs of various forest uses, or (3) areas are
difficult to regenerate after clearcutting. How-
ever, windfall, insects, diseases, and stand con-
ditions impose limitations on how stands can be
handled. A careful appraisal of the capabilities
and limitations of each stand is necessary to
determine cutting practices. Furthermore, par-
tial cutting requires careful marking of indi-
vidual trees or groups of trees to be removed,
and close supervision of logging. The following
recommendations are for partial cutting prac-
tices keyed to broad stand descriptions, wind-
fall risk situations, and disease and insect prob-
lems (Alexander 1972). Practices needed to ob-

tain natural reproduction are also discussed.
Stands are pure pine unless otherwise
indicated.18

Single-Storied Stands19
Description. —

1. Stands may appear to be even-aged (fig. 29),
but often contain more than one age class,
occasionally may even be broad-aged.

2. Codominants form the general level of the
canopy, but the difference in height between
dominants, codominants, and intermediates
is not as great as in spruce-fir stands.

3. If even-aged in appearance:

a. There is a small range in diameter class
and crown length.

b. Live crown length of dominants and
codominants is generally short to
medium (30 to 60 percent of the total tree
height and boles are generally clear for 10
to 40 percent of total tree height).

c. There are few coarse-limbed trees in the
stand.

4. With two or more age classes, the younger
trees usually have finer branches, smaller
diameter, longer live crown, and less clear
bole than older trees.

5. Stocking is generally uniform.

6. A manageable stand of advanced reproduc-
tion is usually absent.

'"In a mixed stand, either less than 80 percent of the
overstory basal area is lodgepole pine, or the overstory is
pine with an understory of a different species.

'^Reproduction less than 4.5 ft tall is not considered a
stand story in these descriptions.

7. In mixed stands, the overstory is either (a)
pure pine or(b) pine and Engelmann spruce,
subalpine fir, or Douglas-fir, with advanced
reproduction of species other than pine that
may or may not be a manageable stand.

Recommended Cutting Treatments. —

Single-storied stands are usually the least wind-
firm because trees have developed together
over long periods of time and mutually protect
each other from the wind.

1. Low windfall risk situations —

The first cut can remove about 30 percent
of the basal area on an individual tree basis.
This initial entry is a preparatory cut that
resembles the first step of a three-cut shel-
terwood, since it probably does not open up
the stand enough for pine reproduction to
become established in significant numbers.
Overstory trees are all about equally suscep-
tible to Slowdown, therefore the general
level of the canopy should be maintained by
removing some trees in each overstory
crown class. The cut should come from C and
D vigor class trees, but openings larger than
one tree height in diameter should be a-
voided by distributing the cut over the entire
area. Do not remove dominant trees that are
protecting other trees to their leeward if
these latter trees are to be reserved for the
next cut. In mixed stands, if the overstory is
pure pine, handle as a pure stand; if the over-
story is of mixed composition, cut as much of
the basal area recommended in pine as is
possible to release the climax species.

The second entry into the stand should not
be made until 5 to 10 years after the first cut
to permit the stand to develop windfirmness.

SINGLE- STORY

The second cut should also remove about 30
percent of the original basal area on an indi-
vidual tree basis. It simulates the second or
seed cut of a three-step shelterwood. The
largest and most vigorous dominants and
codominants should be reserved as a seed
source in stands with the nonserotinous or
intermediate cone habit, but avoid cutting
openings in the canopy larger than one tree
height in diameter by distributing the cut
over the entire area even if it means leaving
trees in the C and D vigor classes with poor
seed production potential. In mixed stands
cut as much of the recommended basal area
in pine as is possible without creating open-
ings larger than one tree height. The last
entry is the final harvest and should remove
all of the remaining original overstory. It
should not be made until a manageable stand
of reproduction has become established, but
the cut should not be delayed beyond this
point if timber production is the primary
concern because the overwood (1) hampers
the later growth of seedlings, and (2) if in-
fected with dwarf mistletoe, will reinfect the
new stand (fig. 30).

The manager also has the option of remov-
ing less than 30 percent of the basal area at
any entry and making more entries, but they
cannot be made at more frequent intervals.
The cut will be spread out and continuous
high forest cover maintained for a longer
period of time. This option is not recom-
mended where mountain pine beetles and
dwarf mistletoe impose limitations on how
stands can be handled.

The usual uniform arrangement of indi-
vidual trees in single-storied stands is not
well adapted to removing trees by
group-selection cutting. Occasionally, how-
ever, natural openings do occur when stands
begin to break up. Also, small openings may
be desirable to meet management objec-
tives. An alternative to removing trees on an
individual basis would be to remove about 30
percent of the basal area in groups. Openings
should be kept small, not more than one to
two times tree height in diameter; not more
than one-third of the area should be cut over
at any one time. This kind of cutting should
be used only in stands where insect and dis-
ease problems are minimal.

The second entry into the stand should not
be made until the first openings have been
regenerated. This cut should also remove
about 30 percent of the original basal area
without cutting over more than an additional
one-third of the area. Openings should be no
closer than about one to two tree heights to
the original openings.

The final entry should remove the remain-
ing groups of merchantable trees. The tim-
ing of this cut depends upon the cone habit
and how the manager elects to regenerate
the openings. If he chooses to use natural
regeneration and the stand is classified as
nonserotinous or intermediate cone habit,
the final harvest must be delayed until the
trees in the original openings are large
enough to provide a seed source.

The manager may choose to remove less
than 30 percent of the basal area and cut over
less than one-third of the area at any one
time. This will require more entries, but each
new cut should not be made until the open-
ings cut the previous entry have regener-
ated. Furthermore, in stands with non-
serotinous or intermediate cone habit, the
last groups cannot be cut until there is either
an outside seed source or the manager elects
to plant these openings.

Figure 30. — New reproduction established after the seed
cut of a shelterwood system in lodgepole pine. Over-
wood should have been removed earlier to release the
reproduction. Fraser Experimental Forest, Colorado.

2. Moderate windfall risk situations —

The first cut should be limited to a light
preparatory cutting that removes about 20
percent of the basal area on an individual-
tree basis. The objective is to open up the
stand, but at the same time minimize the
windfall risk to the remaining trees. Provi-
sion should be made, however, to salvage
blowdowns. This type of cutting resembles a
sanitation cut in that the lowest vigor and
poorest risk trees should be removed, but it
is important that the general level of the
overstory canopy be maintained intact.
Mixed stands should be handled the same as
in low windfall risk situations, except that
less basal area should be removed.

The second entry can be made in about 10
years after the first cut. This entry should
remove about 20 percent of the original basal
area on an individual-tree basis. Windfalls
that were salvaged after the first cut should
be included in the computation of the basal
area to be removed. The objective of this
preparatory cut is to continue to develop
windfirmness while preparing the stand for
the seed cut. Most of the trees marked for
removal should come from the smaller
crown and poorer vigor classes, but maintain
the general level of the canopy intact. In
mixed stands cut as much of the recom-
mended basal area to be removed in pine as is
possible.

It will require about another 10 years to
determine if the stand is windfirm enough to
make another entry. This will be the seed cut,
and should remove about 20 percent of the
original basal area including any windfalls
since the last cutting. The largest and most
vigorous dominants and codominants in
mixed stands and pure stands with non-
serotinous or intermediate cone habit should
be reserved as a seed source, but it is more

important to distribute the cut over the en-
tire area.

The last entry is the final harvest, which
should remove the remaining original over-
story. It cannot be made until a manageable
stand of reproduction has been established.
About 40 percent of the original basal area
will be removed in this cut, and if it is too
heavy (10,000 fbm or more per acre) to be
removed in one harvest without undue dam-
age to the reproduction, the manager must
plan on a final harvest in two steps. The sec-
ond step can begin as soon as skidding is
finished in the first step, if a manageable
stand of reproduction still exists.

The manager also has the option of remov-
ing less than 20 percent of the basal area at
any entry and making more entries, but they
cannot be made at more frequent intervals.

3. High windfall risk situations —

The choice is limited to removing all trees
or leaving the stand uncut. Cleared openings
can be up to about 5 acres, interspersed with
uncut areas. Cutover areas should not ex-
ceed about one third of the total in this risk
situation.

Two-Storied Stands
Description. —

1. Stands may appear to be two-aged (fig. 31),
but can contain more than two age classes.

2. Top story — dominants, codominants, and
intermediates — resembles a single-storied
stand.

3. Second story is composed of younger trees of
smaller diameter — small saw logs, poles, or
saplings — than the top story, but it is always

TWO- STORY

Figure 31. — A two-storied lodgepole pine stand.

below and clearly distinguishable from the
overstory. Trees in the second story are
overtopped and may or may not be sup-
pressed.

4. If more than two-aged, the overstory usually
contains at least two age classes. The
younger trees are finer limbed and may be
smaller in diameter than the older trees. The
second story may also contain more than one
age class.

5. Stocking of the overstory may be irregular,
but overall stocking is usually uniform.

6. A manageable stand of advanced reproduc-
tion is usually absent.

7. In mixed stands, the overstory is usually
pure pine, but occasionally it may be pine
with spruce or Douglas-fir. The second story
is usually spruce and fir at the higher eleva-
tions, and Douglas-fir at the lower eleva-
tions.

8. Stocking in mixed stands may vary from un-
iform to irregular.

9. Mixed stands may have a manageable stand
of advanced reproduction of species other
than pine.

Recommended Cutting Treatments. — Same
as for three-storied stands.

Three-Storied Stands
Description. —

1. Stands may appear to be three-aged (fig. 32),
but they can contain more than three age
classes, although stands are seldom broad-
aged.

2. Top story resembles a single-storied stand
except that there are fewer trees.

3. The second and third stories consist of
younger, smaller diameter trees. Second
story may be small saw logs or large poles,

while the third story is likely to be composed
of small poles or saplings. Second and third
stories are overtopped, and some trees may
be suppressed.

4. Overall stocking is likely to be uniform, but
stocking of any story may be irregular.

5. A manageable stand of advanced reproduc-
tion is usually absent.

6. In mixed stands the top story may be either
pure pine or a mixture of pine and other
species. The second story is usually spruce
and subalpine fir at the higher elevations,
and Douglas-fir at the lower elevations. The
second story may occasionally contain some
pine, but it is rarely pure pine. The third
story is almost always composed of species
other than pine.

7. Stocking in mixed stands can vary from un-
iform to irregular.

8. Mixed stands often have a manageable stand
of advanced reproduction of species other
than pine.

Recommended Cutting Treatments (Two- and
Three-Storied Stands). — Trees in the top story
are usually more windfirm than those in a
single-storied stand. Trees in the second and
third stories are usually less windfirm than
trees in the top story.

1. Low windfall risk situations —

The first cut can remove up to 50 percent
of the basal area in two-storied stands
(providing not more than half of the basal
area removed comes from the top story), and
up to 40 percent of the basal area from
three-storied stands. This cutting is as heavy
as the first or seed cut of a two-cut shelter-
wood, but marking follows the rules for
individual-tree selection. Heavier cutting
may be possible in three-storied stands, but

the appearance of a continuous overstory is
not likely to be retained. Trees removed
should be in vigor classes C and D insofar as
possible, but since the top story is likely to be
more windfirm, selected dominants and
codominants should be left even when they
are in vigor classes C and D, if they do not
have dead or dying tops. Avoid cutting holes
in the canopy larger than one tree height in
diameter by distributing the cut over the en-
tire area. Do not remove dominant trees that
are protecting other trees to their leeward if
these latter trees are to be reserved for the
next cut. In mixed stands, if the top story or,
rarely, the first and second stories are pure
pine, handle as a pure stand. If the top story
is of mixed composition, cut as much of the
basal area to be removed in pine as is possi-
ble to release the climax species, but do not
cut all of the pine if it is needed to maintain
the overstory.

The second entry should be the final
harvest to remove the remaining original
stand and release the reproduction. It
cannot be made until the new stand of re-
production is established. If the residual
volume is greater than about 10,000 fbm
per acre, the final harvest should be made in
two steps to avoid undue damage to newly
established reproduction. The second step
can begin as soon as skidding is finished in
the first step, if a manageable stand of re-
production still exists.

If there is a manageable stand of advanced
reproduction under mixed stands, the first
cut can be an overstory removal if the vol-
ume is not too heavy. Otherwise, the first cut
can remove 40 to 50 percent of the basal area
on an individual-tree basis as long as the
more windfirm dominants and codominants
are left. The timing of the second cut is not
critical from a regeneration standpoint so
long as a manageable stand of reproduction
still exists after the first cut and can be
saved.

The manager has other options to choose
from. He may elect to cut less than the rec-
ommended basal area, make more entries,
and spread the cut out over a longer period of
time by delaying the final harvest until the
new stand is tall enough to create the ap-
pearance of a high forest. This is not recom-
mended where mountain pine beetles and
dwarf mistletoe limit how stands can be
handled.

In pure or mixed stands with irregular
stocking that may have resulted from the
breakup of single-storied stands, old beetle
attacks, or windfall losses, an alternative
first cut can remove about 40 percent of the

basal area in a modified group selection. The
group openings can be larger (two to three
times tree height) than in single-storied
stands, but the area cut over should not ex-
ceed about one-third of the total. Openings
should be irregular in shape without wind-
catching indentations in the borders. This
kind of cutting is not applicable in pure
stands where mountain pine beetle or dwarf
mistletoe impose limitations, because the in-
terval between initial cutting and final har-
vest is likely to be too long to prevent serious
mistletoe infection of new reproduction
and/or loss of beetle-susceptible trees.

Two additional entries can be made in the
stand. They should each remove about 30
percent of the original basal area in group
openings up to two to three times tree height,
but not more than one-third of the area
should be cut over at any one time. If there is
not a manageable stand of advanced repro-
duction, the manager must wait until the
first openings are regenerated before cut-
ting the second series. Furthermore, in
mixed stands, or pure stands with the non-
serotinous or intermediate cone habit, he
must either delay cutting the final groups
until there is a seed source or plan on plant-
ing these openings. If there is a manageable
stand of advanced reproduction, the timing
between cuts is not critical from a regenera-
tion standpoint.

The manager has the option in mixed
stands of removing less than the recom-
mended basal area and cutting less than the
recommended area at any one time. This will
require more entries and spread the cut out
over a longer period of time.

2. Moderate windfall risk situations —

The first entry should be a preparatory cut
that removes not more than 30 percent of the
basal area on an individual-tree basis. Pre-
dominants, and codominants and inter-
mediates with long live crowns should be
removed first. The remaining cut should
then come from trees in vigor classes C and
D. Maintain the general level of the canopy
by not cutting holes larger than one tree
height in diameter in the canopy. Provision
should be made to salvage blowdowns.
Mixed stands should be handled as in low
wind risk situations, except that less basal
area should be removed.

The second entry should not be made in
less than 10 years. This cut should remove
about 30 percent of the original basal area,
including the salvage of any windfalls after
the first cut. The second entry is the seed cut.

The best dominants and codominants should
be reserved as a seed source in stands with
the nonserotinous or intermediate cone
habit, but it is important that the cut be dis-
tributed over the entire area.

The next entry is the final harvest to re-
move the remaining merchantable volume
and release the new reproduction after it has
become established. However, if the re-
sidual stand has too heavy a volume, the final
harvest should be made in two steps.

In mixed stands that contain a manageable
stand of reproduction, and if the volume per
acre is not too heavy, the first cut can be an
overwood removal. If the volume is too
heavy for a one-step removal, the manager
should follow the recommendations for pure
stands because the wind hazard is too great
to permit a two-step removal in a stand that
has not been previously opened up to develop
windfirmness.

3. High windfall risk situations —

The choice is limited to either removing all
the trees or leaving the stand uncut. Cleared
openings can be up to about 5 acres, in-
terspersed with uncut areas. The cutover
area should not exceed about one-third of the
total in this risk situation.

the overstory trees varies from poor to good.

3. In stands that developed from deterioration
of single- or two-storied stands, the over-
story trees may be no limbier than the fill-in
trees. Nearly all of the healthy, faster grow-
ing trees are below saw-log size.

4. Stocking may be irregular.

5. A manageable stand of advanced reproduc-
tion may be present.

6. In mixed stands, the overstory may be either
(1) pure pine, or (2) a mixture of pine, spruce,
and fir at the higher elevations, or pine and
Douglas-fir at lower elevations. Understory
trees have the same characteristics as pure
stands except that the composition is likely
to be other than pine.

7. Stocking in mixed stands is more likely to be
irregular.

8. Mixed stands frequently have a manageable
stand of advanced reproduction of species
other than pine.

Recommended Cutting Treatments. — These
are usually the most windfirm stands, even
where they have developed from the deteriora-
tion of single- and two-storied stands. By the
time they have reached their present condition,
the remaining overstory trees are likely to be
windfirm.

1. Low to moderate windfall risk situations —

Multi-Storied Stands
Description. —

1. Stand is usually broad-aged (fig. 33) with a
wide range in diameters.

2. If stands developed from relatively few in-
dividuals following disturbance, the over-
story trees are coarse limbed. Fill-in trees
are better formed and finer limbed. Vigor of

There is considerable flexibility in har-
vesting these stands. All size classes can be
cut, with emphasis on either the largest or
smallest trees in the stand. The first cut can
range from an overwood removal to release
the younger growing stock to a thinning from
below to improve the spacing of the most
vigorous of the larger trees. Thereafter, cut-
ting can be directed toward either even-aged
or uneven-aged management. In mixed

MULTI — STORY

Figure 33. — A multi-storied lodgepole pine stand.

stands the first cut should be an overwood
removal of the pine to release the climax
species. The understory trees should be
thinned to improve spacing.

2. High windfall risk situations —

The safest first cut is an overwood re-
moval with a light thinning from below to
obtain a wider spaced, more open stand that
can develop windfirmness. Thereafter, cut-
ting can be directed toward either uneven- or
even-aged management.

Modification to Partial Cutting Practices
Imposed by Disease and Insect Problems

Dwarf mistletoe. —

1. Cut only in stands where the average mis-
tletoe rating is two or less (see fig. 24), and
remove only the percentage of basal area
recommended for the stand description and
windfall situation. In single-storied stands,
where site index is 70 or above, trees in the
intermediate and lower crown classes should
be removed first in preference to dominants
and codominants. If site index is below 70,
trees in all crown classes are about equally
susceptible to infection. In two- and
three-storied stands, as much of the first cut
as is possible should come from the second
and third stories because these trees are
likely to be more heavily infected than the
top story. In single-, two-, and three-
storied stands, the final overstory removal
can be delayed until the new reproduction is
tall enough to provide a forest aspect. To
minimize infection of new reproduction
however, time interval should not exceed 30
years after the regeneration cut when the
average mistletoe rating is one, or 20 years
when the rating is two. Provision should be
made to sanitize the young stand at the time
of final harvest. In multi-storied stands, the
safest procedure is an overwood removal
with a cleaning and thinning from below.

2. In old-growth stands with an average mis-
tletoe rating greater than two, any partial
cutting, thinning, or cleaning is likely to in-
tensify the infection. The safest procedure,
therefore, is to either remove all of the trees
and start a new stand or leave the stand
uncut. If the manager chooses to make a par-
tial cut for any reason, the initial harvest
should be heavy enough to be a regeneration
cut. All residual trees must be removed
within 10 years after the first cut, and provi-
sion made to sanitize the young stand at that
time.

Comandra Blister Rust. — Cut as many trees
with stem cankers and spike-tops as possible in
the first cut without removing more than the
recommended basal area or cutting large open-
ings in the canopy. Since the rate of spread in
mature trees is relatively slow and the disease is
not transmitted from pine to pine, leaving a few
infected trees is less of a risk than opening up
the stand too much.

Mountain Pine Beetle. —

1. If the insect is present in the stand at an
endemic level, or in adjacent stands in suffi-
cient numbers to make successful attacks,
and:

a. Less than the recommended percentage
of basal area to be removed in the first cut
is in susceptible trees, any attacked tree
and all of the most susceptible trees
should be removed in the first cut. This
will include most of the trees 12 inches
d.b.h. and larger, and all trees 10 to 12
inches d.b.h. in vigor classes A and B.
Provision should be made to salvage at-
tacked trees, and the second cut should be
made within 10 years of the first cut.

b. More than the recommended percentage
of basal area to be removed in the first cut
is in susceptible trees, the manager has
three options: (1) remove all the trees, (2)
remove the recommended basal area in
attacked and susceptible trees and accept
the risk of future losses, or (3) leave the
stand uncut. If the stand is partially cut or
left uncut, some trees from 7 to 12 inches
d.b.h. and most trees below 7 inches d.b.h.
will survive.

2. If the stand is sustaining an infestation that
is building up, and the manager chooses to
either partially cut or leave the stand uncut,
he must accept the risk of an outbreak that
could destroy most of the merchantable
stand.

Cutting to Save the Residual

In mixed stands and to a lesser extent pure
stands, the manager must determine whether
he has an acceptable stand of advanced repro-
duction and decide if he is going to manage it
before any cutting begins. Furthermore, he
must reevaluate the advanced reproduction
after the final harvest and slash disposal to de-
termine the need for supplemental stocking.
The same criteria used to evaluate advanced
reproduction on spruce-fir clearcuts applies
here.

In partial cutting, protection of the residual
from logging damage is of primary concern.
The residual includes merchantable trees left
after shelterwood cutting, and advanced repro-
duction in both shelterwood and group-selection
cutting where an acceptable stand is to be man-
aged. Protection begins with a well-designed
logging plan at the time of the first cut. To
minimize damage, skidroads must be laid
out — about 200 ft apart depending on the
topography — and marked on the ground. These
skidroads should be kept narrow, and located so
that they can be used to move logs out of the
woods at each cut. Close supervision of logging
will be required to restrict travel of skidding
and other logging equipment to the skidroads.
In shelterwood cuttings, trees should be felled
into openings as much as possible using a her-
ringbone pattern that will permit logs to be pul-
led onto the skidroads with a minimum of dis-
turbance. It may be necessary to deviate from
the herringbone felling angle in order to drop
trees into openings. If this is the case, the logs
should be bucked into short lengths to reduce
skidding damage. Trees damaged in felling and
skidding should not be removed if they are still
windfirm. In group-selection cutting, the felling
pattern should be similar where there is a man-
ageable stand of advanced reproduction.
Otherwise all trees should be felled into the
openings. Both shelterwood and group-
selection cuttings require close coordination
between felling and skidding because it may be
necessary to fell and skid one tree before
another tree is felled.

Slash Disposal and Seedbed Preparation

Some treatment of logging slash and unmer-
chantable material will probably be needed
after each cut. Treatment should be confined to
concentrations and that needed to reduce visual
impact, however, because most equipment now
available for slash disposal is not readily adapt-
able to working in shelterwood cuttings. Furth-
ermore, burning slash will not only cause dam-
age to the residual, but may destroy the seed
supply in stands with serotinous cones. Skid out
as much of the down sound dead and green cull
material as possible for disposal at the landings
or at the mill. Treatment in stands should be
limited to lopping and scattering, chipping
along the roadway, and hand piling and burning
to minimize damage. In group-selection cutting,
if there is not a manageable stand of advanced
reproduction, dozers equipped with bush blades
can be used to concentrate slash for burning in
the openings. Piles should be kept small to re-
duce the amount of heat generated. Stands with

the serotinous cone habit should not be treated
until the cones have had time to dry out and open
up.

On areas to be regenerated by new reproduc-
tion, a partial overstory canopy or trees stand-
ing around the margins of small openings pro-
vide two of the basic elements necessary for
regeneration success in stands with the non-
serotinous or intermediate cone habit — a seed
source within effective seeding distance, and an
environment compatible with germination, ini-
tial survival, and seedling establishment. In
stands with the serotinous cone habit, the seed
supply is largely in the cones attached to the
slash or scattered on the ground. The manager
must make sure that the third element — a suit-
able seedbed — is provided after the regenera-
tion cut where shelterwood cutting is used, and
after each cut where group selection is used.
Unless at least 40 percent of the available
ground surface is exposed mineral soil after
logging and slash disposal, additional seedbed
preparation is needed. Until special equipment
is developed, seedbed preparation as well as
slash disposal will pose problems. The equip-
ment available is too large to work well around
standing trees. Small dozers or other machines
equipped with brush blades will have to be used,
but they must be closely supervised to minimize
damage to the residual.

Multiple-Use Silviculture

Timber production is only one of the key uses
of lodgepole pine forests in the central Rocky
Mountains. They occupy areas that also are im-
portant for water yield, wildlife habitat, recrea-
tion, and scenic beauty. Forest managers must
consider how these areas are to be handled to
meet the increasing demands of the public. The
kinds of stands that appear desirable for in-
creased water yields, preservation of the forest
landscape, maintenance of scenic values, and
improvement of wildlife habitat have been sug-
gested in a general way by both research and
observation.

WATER

Snowfall is the key to water yield in lodgepole
pine forests. Comparisons on the Fraser Ex-
perimental Forest in Colorado have shown that
more snow accumulates in cutover areas than
under adjacent uncut stands. Accumulations
are greatest on plots that are clearcut (Wilm and
Dunford 1948, Hoover and Leaf 1967). The in-
creased snow depth is not additional snow, how-
ever, but a redistribution of snow. Wind trans-
ports the snow intercepted on the surrounding

trees and deposits it in the openings. Some of the
increase in water equivalent in the openings is
available for streamflow (Hoover and Leaf
1967).

Research and experience suggest that a round
or patch-shaped opening, about five to eight
times trees height in diameter, is the most ef-
fective for trapping snow (Hoover 1969). In
larger openings, wind is likely to dip down to the
ground and blow the snow out of the openings.
About one-third of the forest area in openings
distributed over the watershed appears to be
the best arrangement. These openings could
either be maintained permanently or regener-
ated to new growth that would be periodically
recut when trees reach about half the height of
the surrounding trees. The remaining two-
thirds of the area should be retained as continu-
ous high forest, since the taller trees control
snow deposition. Trees would be periodically
harvested on an individual-tree basis or in small
groups (one to two times tree height) to gradu-
ally replace the old with a new stand. Ulti-
mately, the reserve stand would approach a
broad-aged structure with the overstory canopy
remaining at about the original height.

An alternative would be to make a light cut
distributed over the entire watershed, remov-
ing about 20 to 30 percent of the basal area on an
individual-tree basis or in small groups. The ob-
jective is to open up the stand enough to develop
windfirmness, and salvage low-vigor and poor-

risk trees. Openings five to eight times tree
height can then be cut on about one-third of the
area. The remaining two-thirds of the area
would be retained as permanent high forest,
with trees periodically removed on an
individual-tree basis or in small groups.

Another alternative that would integrate
water and timber production would be to har-
vest all of the old growth on a watershed with a
series of cuts spread over a period of 120 to 160
years. At intervals of about 20 to 40 years, a
portion of the area would be harvested in small
openings — four to five times tree
height — distributed over the watershed. The
number of openings cut at each interval would
depend on the size of the watershed and the
length of rotation and cutting cycle selected.
These openings would be regenerated (fig. 34)
so that at the end of one rotation, the watershed
would contain groups of trees in several age
classes from reproduction to those ready for
harvest. The tallest trees may be somewhat
shorter than the original overstory, but the ad-
verse effects on snow deposition should be
minimized by keeping the openings small. At
the end of one rotation, the forest manager has
the option of following the same procedure
through the next rotation, or selecting about
one-third of the openings to be maintained as
snow-trapping areas, and converting the re-
maining area into a broad-aged stand by period-
ically removing individual trees.

Figure 34. — New reproduction established in a cleared opening about four to
five times tree height in lodgepole pine. Next series of group openings should be
cut. Fraser Experimental Forest, Colorado.

WILDLIFE

The use of lodgepole pine forests by deer is
influenced by timber cutting practices. On the
Fraser Experimental Forest, there was more
deer use and a greater abundance and selection
of forage species on clearcut openings than
under adjacent uncut stands (Wallmo 1969,
Wallmo et al. 1972); openings 3 chains wide were
used more than either wider or narrower open-
ings. Forage production appears to decline
about 10 years after cutting, however, as tree
reproduction replaces forage species (Wallmo
et al. 1972). Similar trends in forage production
have also been observed on lodgepole pine
clearcuts in Montana (Basile and Jensen 1971).
Wallmo suggests that new openings be cut
periodically.

An alternative would be to cut about one-sixth
of a cutting block every 20 years in openings
about four to five times tree height. Each Work-
ing Circle would be subdivided into a number of
cutting blocks (of at least 300 acres) so that not
all periodic cuts would be made in a single year
on a Working Circle. Such periodic cutting
would provide a good combination of numbers
and species of palatable forage plants and the
edge effect desired, while creating a several-
aged forest of even-aged groups, thus integrat-
ing wildlife habitat improvement with timber
production.

Observations on the Medicine Bow National
Forest in Wyoming indicate that both natural
and cleared openings in lodgepole pine forests
are heavily used by elk for grazing and
calving.20 The size of opening does not appear to
be critical, but openings interspersed with
standing timber that can be used for ruminat-
ing, resting, and hiding are preferred. Since
openings cut in the canopy are not likely to re-
tain a high proportion of palatable forage
species for long periods of time, new openings
should be cut while allowing the older ones to
regenerate.

Other wildlife, including nongame animals,
living in lodgepole pine forests are affected by
the way these forests are handled. In general,
their habitat requirements include a combina-
tion of openings and high forest to provide food,
cover, and edge. With protection from wildfires
many stands have become denser, and repro-
duction has filled in the openings. Some reduc-
tion in stand density is needed to create or im-
prove wildlife habitat. Small, irregular open-
ings (about four to five times tree height) cut in

"'Personal communication with A. Lorin Ward, Wild-
life Biologist, Rocky Mt. For. and Range Exp. Stn., Fort
Collins, Colo.

the canopy at periodic intervals would open up
the stand and provide the food, cover, and edge
needed.

RECREATION AND ESTHETICS

Permanent forest cover — at least in
part — is preferred in travel influence zones,
and in areas of high recreational value and out-
standing scenic beauty. Unfortunately, old-
growth lodgepole pine stands are not likely to
persist in a sound condition indefinitely. Where
stand conditions and wind, insect, and disease
problems permit, some form of partial cutting
will retain forest cover while at the same time
replacing the old with a new stand. However,
the visual impact of logging operations — haul
roads, damage to residual trees, and slash and
debris — must be minimized. In situations
where there is no alternative to clearcutting,
and the environmental impact of clearcutting is
unacceptable, there is no choice but to leave the
stands uncut.

To reduce the sudden and severe visual im-
pact on the landscape viewer, openings cut in
stands for timber and water production, wildlife
habitat improvement, and recreation (ski runs)
should be a repetition of natural shapes, visually
tied together to create a balanced, unified pat-
tern that will complement the natural landscape
(Barnes 1971). Such a pattern is especially im-
portant for openings in the middle and back-
ground that can be seen from distant views. The
foreground should be maintained in high forest
under some partial cutting system (again,
where stand conditions and wind, insect, and
disease problems permit).

MANAGEMENT OF YOUNG GROWTH

Throughout the Rocky Mountains there are
extensive areas of second growth. These stands,
which resulted from past fires or cutting, are
between 1 and 120 years old. Many are badly
crowded and in need of thinning to bring them
under management. Some have been thinned at
least once, but all need further reduction in
stand density to maintain or reclaim lo^t
growth.

Stand Description

Young stands may be pure or mixed. Pure
stands are usually single-storied and even- or
two-aged. Two-aged stands are occasionally
two-storied with pine in the overstory and
spruce, subalpine fir, or Douglas-fir in the un-

derstory. Pure stands are most often over-
stocked, while mixed stands may be patchy. In
the thinning practices described below, no dis-
tinction is made between species. Trees with
the best form and vigor, and free of disease
should be left.

Thinning Practices

In stands with less than 2,500 stems per acre,
the first thinning can be delayed until age 30
years. If the stand is 10 years old and the stock-
ing is less than 1,000 stems per acre, the man-
ager should consider fill-in planting to raise
stocking to 1,500 stems per acre. The level of
growing stock to be retained at age 30 will de-
pend upon management objectives. Use the
procedures developed by Myers (1971) to ex-
amine the possible alternatives. Select the
growing stock level and cutting cycle that best
meet the management goals for the particular
combination of age, diameter, height, site qual-
ity, stand density, and past growth.

If the stand contains more than 2,500 stems
per acre, it should be thinned at age 10 to 20
years. The first thinning should leave about
1,500 stems per acre. This density is needed to
promote height growth in young stands. The
second thinning should be made at age 30 years.
The spacing will depend upon management ob-
jectives. Use the procedures developed by
Myers (1971) to examine possible alternatives.
From past growth in relation to diameter,
height, age, density, and site quality, determine
future growth for different combinations of
growing stock and cutting cycles. Select the ap-
propriate combination that best meets man-
agement goals.

If stands are 40 to 70 years old, wider spacings
are recommended because height growth has
been established, and that lost by crowding can-
not be recovered. Some of the diameter growth
can be recovered, however. Develop the neces-
sary working tools from stand examination, and
use the simulation program developed by
Myers (1971) to produce a series of yield tables
for different combinations of growing stock
levels and cutting cycles. Select the combina-
tion that best meets management goals for the
particular site and stand conditions.

Thinning in stands older than 70 years is not
recommended unless original stand density was
less than 2,500 stems. Even then the value of
thinning is questionable because the cost is not
likely to be recovered in terms of increased vol-
ume production.

WHAT DO WE NEED TO KNOW

Silvicultural practices are needed that will
establish and maintain subalpine forest stands
with the form, structure, and arrangement
needed to integrate all land uses. For the timber
resource, these needs include: (1) the ability to
classify subalpine forests into categories of
similar characteristics as the basis for identify-
ing management potentials in existing stands;
and (2) tests of new and modified silvicultural
systems and cultural practices in stands of dif-
ferent characteristics.

The classification of vegetation in subalpine
forests is needed to guide the manipulation of
stands for multiple use. For the timber re-
source, this classification should include: (1)
what species grow together, and how to recog-
nize the plant associations; (2) how these
species reproduce, grow, and interact in a vari-
ety of situations; (3) successional trends and
stability of various plant associations in re-
sponse to different management prescriptions;
and (4) the extent to which research results can
be extrapolated.

Prediction of growth and yield of even-aged
spruce-fir is needed to provide the basis for
decisions on (1) site quality classes that will
repay the cost of thinning and other cultural
treatments; (2) levels of growing
stock — including frequency of thinnings and
intermediate cuttings — to meet different
management objectives; (3) length of rotation
cutting cycles, and allowable cut for different
cutting methods, management goals, and utili-
zation standards, and (4) the place of timber
management in multiple-use management.
Managers can make better decisions about key
uses when they can forecast timber potential
under alternative management systems. The
field and computer simulation techniques now
available for the management of even-aged
stands must be expanded to include uneven-
aged stands and irregular stand structures
needed for multiple use.

Methods of obtaining natural and artificial
reproduction of Engelmann spruce have been
largely directed toward regenerating cleared
openings. While adequate regeneration practice
can be prescribed in most instances, informa-
tion is still needed on: (1) relationships between
the kind of seed source and the amount and
periodicity of seed production; and (2) germina-
tion and survival under different environmen-
tal conditions to identify limiting factors and
provide estimates of the probability of seedling
establishment. These data, together with exist-
ing information on seed dispersal distances will
permit simulation of the regeneration phase of
spruce for different environmental conditions.

Methods of obtaining regeneration are usu-
ally adequate for lodgepole pine stands with
serotinous cones. What is needed now are
natural and artificial reproduction procedures
for stands with nonserotinous cones, especially
on south slopes and in tension zones.

There is a need to use quantitative data from
existing knowledge in current resource and
prediction response simulation models to aid
multiple-use planning and decisionmaking.
These models will also identify deficiencies in
knowledge where additional work is needed to
determine basic processes and interrelation-
ships among various resources and manage-
ment practices. We must pinpoint and fill in
these gaps in our knowledge before we can de-
velop more refined multi-resource response
models.

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PESTICIDE PRECAUTIONARY STATEMENT

This publication reports research involving pesticides.
It does not contain recommendations for their use, nor
does it imply that the uses discussed here have been
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appropriate State and/ or Federal agencies before they
can be recommended.

CAUTION: Pesticides can be injurious to humans,
domestic animals, desirable plants, and fish or other
wildlife — if they are not handled or applied properly.
Use all pesticides selectively and carefully. Follow rec-
ommended practices for the disposal of surplus pesticides
and pesticide containers.

H i. iiniTHfHr or agiicultuie

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