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“Tt ‘LOGGING RESIDUES

ON SAW LOG OPERATIONS,
ARIZONA AND NEW MEXICO

Theodore S. Setzer, Alvin K. Wilson, * AGRICULTURE
and Grover A. Choate ML LIBRARY

USDA Forest Service
Research Paper INT-78, 1970

INTERMOUNTAIN FOREST AND RANGE EXPERIMENT STATION
Ogden, Utah 84401

COVER PHOTO

Although the longbutt shown has a large rot colwm,
tt also has a measurable volume of sound wood, which
may be salvageable.

USDA Forest Service
Research Paper INT-78, 1970

LOGGING RESIDUES
ON SAW LOG OPERATIONS,
ARIZONA AND NEW MEXICO

Theodore S. Setzer, Alvin K. Wilson, and
Grover A. Choate

INTERMOUNTAIN FOREST AND RANGE
EXPERIMENT STATION

Ogden, Utah 84401

THE AUTHORS

THEODORE S. SETZER specializes in the products and
timber removals phase of the Forest Survey Unit
at Intermountain Forest and Range Experiment Sta-
tion. Before coming to the Intermountain Station
in 1965 he spent a number of years as a sawmill
operator and also some time in forestry research
and conservation planning.

ALVIN K. WILSON designs and conducts special studies
for Forest Survey at the Intermountain Forest and
Range Experiment Station in Ogden, Utah. After
working in Forest Survey at the Northeastern
Forest Experiment Station, he spent several years
in forest management research for the Intermoun-
tain Station and returned to Forest Survey work in
1957. He is the author of numerous publications on
forest management and forest resources.

GROVER A. CHOATE was, at the time of writing this
publication, Principal Resource Analyst for Forest
Survey at the Intermountain Forest and Range Ex-
periment Station, Ogden, Utah. His career in-
cludes work in the Lake States, Washington, D. C.,
the Pacific Northwest, and Southeast Asia. He
retired from the Forest Service in late 1969.

12

CONTENTS

Page
TNE TOUD UCP IGIN chee eh wits © 5) se Se le ele ow pee 1
EVE NIOV Ale OLN AG. Goel © 6 2 2 te oe 8 Oe we 2

LOGGING RESIDUES AND PRODUCT VOLUME ... 4

DIANE Ein C RASS REMOVALS. . 0 6 i. ee a ee 5)
SURVEY METHODS AND RELIABILITY

OS SIA TGS sos wis io io Fs yao: Pacem de; alys.. oy sce 6
TERMINOLOGY *. 20 5°. MahGee otter te te 36. ae te teh % Ver 10

*Note: See Terminology for definitions of many
of the terms used in this paper.

TABLES

Page

1.--Conversion factors to estimate total net
removals from inventory, Arizona and
INE Wile SICO. sane io ager aie a ew SOUS oalee oe eee 53

2.--Net volume of logging residues from saw log
operations as a percent of net product volume,
Arizona: and New MexiCO: . ..6. i << 0 6 8 6.6 5

3.--Growing stock trees removed from inventory
in saw log operations per 1 thousand cubic
feet of net product volume, Arizona and
EMG SE NC ee ee ea ee ae a ee ere 7

4,--Standard errors of ratios for logging residue

volumes by net cubic- and board-foot measures,
Arizona anc New MEXICO). 9. 66 6 bow «we eee 9

alg

ABSTRACT

Reports results of a survey made of logging operations
to estimate the volume of logging residues in relation to
the volume of saw logs harvested in Arizona and New
Mexico. Results show: conversion factors that can be
applied to product volume to estimate total removals from
inventory; residue volume as a percentage of saw log vol-
ume; the relative importance of felling and skidding as
causes of residues; and the numbers of trees removed
from growing stock inventory by logging. Survey methods
and reliability of data are discussed.

1V

INTRODUCTION

The volume of timber cut or killed during logging
operations and left in the woods represents a reduc-
fon in the anventory volume available for future
management and harvesting. Consequently, the volume
of unused timber should be taken into consideration
it difrerences between Successive inventories are to
be more fully understood. Estimates of the amount of
logging residue potentially marketable as chips are
OL imterest also,

in wsoss Forest Survey at the Intermountain
Forest and Range Experiment Station conducted a survey
of logging residues in Arizona and New Mexico. Log-
gine wesidue Surveys yield various types of infor=
mation,! but only data considered to be sufficiently
reliable sor puULpOSeSs 01 Chis; report were used here.
Information not included in the present paper may be
combined with data from future residue surveys of
@ther areas to provide adequate reliability for fur-
ther analyses. Since 1965, Forest Survey has surveyed
logging residues in Idaho, Montana, Colorado, Utah,
Wyoming, and in South Dakota west of the 103d meridian.
if present plans’ are adhered to, residues will be re-
surveyed periodically in all Mountain States.

7

1Conversion factors to be applied to product vol-
umes for estimates of total volumes removed from in-
ventory in commercial logging; average conversion
factors used. to express product volume in several
units of measure (cubic feet, International 1/4-inch
rule, -and ‘Scribner log. rule); the diameter distribu-
tion of trees removed from inventory by logging; the
proportion of timber products harvested from growing
stock trees compared to that of products from non-
growing stock trees; cull and breakage losses by
species; the relative importance of felling and skid-
ding as causes of residues; and the proportion of
logging residue volume made up of pieces of various
SiZewclassese

This report includes statistics for New Mexico
and Arizona and for the two States combined.

REMOVAL ESTIMATES

Expansion factors are computed to permit calcu-
lation of the inventory that remains following com-
mercial logging operations. To adjust the inventory,
removals (volume of products plus residues from fell-
ing and skidding) must be subtracted from the pre-
logging inventory. However, the removal volume should
omit material that was not included in the inventory,
i.e€., the portions of treejstems overutalazediby ein
ventory standards. Such material can come from cut-
ting below the minimum stump height (1 foot by Forest
Survey standards) or from harvesting product volume
beyond specified top diameters. It also can come from
harvesting saw logs from growing stock trees of less
than the sawtimber size specified for inventory or by
cutting roundwood products from cull trees.

Overutilized material (by Forest Survey standards)
was excluded from the removal volume when the conver-
Sion factors shown in table 1 were developed. How-
ever, the overutilized volume normally is part of the
reported product volume to which these factors will
be applied.

Therefore:

: removal volume ‘ ,
conversion factor = —————., which is
product volume

equivalent to

net product volume (excluding overutilization)
+ residue volume
product volume (including overutilization)

In the Arizona-New Mexico area, as well as in each
of these States individually, the net volume of timber
removed from growing stock inventory averages 1.12
times the cubic-foot volume of saw logs harvested
(Gable- 1);

Table 1.--Converston factors to esttmate total net
removals from tnventory, Artzona and New Mextco

Unit of measurement

and : Arizona : New Mexico : Atizona-

minimum top diameter : : ; New Mexico
Cubic foot Eeh22 datli22 Lei Z2

4 inches
Board foot! 1.052 1.063 1.056

Variable
Board foot! 1.051 1.061 1.055

7 inches

1International 1/4-inch log rule.

Factors for estimating removals from sawtimber2
in inventory are somewhat smaller numerically than
the factors used for estimating removals from growing
stock. Factors derived for board-foot measurements
to the minimum variable top standards used by Forest
Survey (see Sawttmber volume in Terminology) are not
much different from those derived for the minimum fixed
top of 7 inches. By both top diameter standards,
conversion factors used to estimate removals in Ari-
zona and New Mexico combined amount to 106 percent of
saw log volume; the proportion. for either State™is
Similar.

Correction factors are numerically less for board-
foot measure than for cubic-foot measure because con-
siderable material scaled as net cubic-foot residue is
not included in the net board-foot scale. Such mater-
ial consists of (1) the upper stem portion beyond the
minimum top diameter for board-foot measure, (2) the
volume in destroyed growing stock trees of less than
Sawtimber size, and (3) portions of sound trees that
are cull (because of crook) for saw logs.

2Board-foot volumes used in this report are
International 1/4-inch log rule volumes.

LOGGING RESIDUES
AND PRODUCT VOLUME

The net volume of logging residues represents
underutilization by one standard or another. By Forest
Survey's cubic-foot standards, residues include all
unused net volume between a 1-foot stump and a 4-inch
minimum top diameter inside bark (d.i.b.). By board-
foot standards, net residue volume consists of unused
material in sawtimber trees from a 1-foot stump to
either the variable or the fixed top diameters. Mer-
chantable logs missed in skidding are included in saw-
timber residues.

The net volume of logging residues from harvesting
a given volume of saw logs can be estimated by the use
of table 2. For example, resadues ‘from the zeportved
1966 harvest of 61,813 MCF of saw logs from growing
stock in Arizona are estimated to be:

61S LS Xs OFLZZ0F = 7.7 MMCE-

The largest part of residue volume results from
felling. Most of this is material from trees from which
saw logs have been cut. Skidding losses are relatively
minor and, as shown by the following tabulation, amount
to less than 20 percent of cubic-foot residue volume in
the Arizona-New Mexico area, as well as in each of the
two States.

Felling
Product Other All

trees trees trees Skiddtng Total

-----+--- Pereent - ----- -
Arizona 74.20 6.78. 280.98 T9 02 100.00
New Mexico 70m 15542 penne 14.05 100.00

Arizona-
New Mexico TOATE LOR225 482.96 Tere sO! 100.00

Table 2.--Wet volume of logging restdues from saw log
operattons as a percent of net product volume,
Artzona and New Mextco

Unit of measurement : : e
and : Arizona : New Mexico : , en
minimum top diameter : : . New Mex1co

Cubic foot 12.20 ers 12-89
4 inches

Board foot! 627 6.36 eeO
Variable

Board foot! Sell 6.15 5.52
7 inches

lInternational 1/4-inch rule.

It should be pointed out that residue volumes
Gerived by tne useue “tractors in table’ 2 are not
totally available for chipping. A more detailed and
intensive survey would be necessary to assess residue
characrerist1es andeco determine what portion of these
residues could be used under prevailing market
conditions.

DIAMETER CLASS REMOVALS

Information on the number of growing stock trees
harvested or destroyed? in each diameter class is
essential for derivations of diameter class cutting
rates used in most stand-table projections of growth
and inventory. Reliable data of this kind usually are
difficult to’ obtain. However, logging residue surveys
provide means tox estimating the distribution of trees
removed per unit volume of saw logs harvested.

3Either occurrence removes the trees from
inventory.

Table 3 shows the total number of growing stock
trees (product trees and others), removed per 1 MCF
of product volume in New Mexico, in Arizona, and in
the New Mexico-Arizona area. These figures can be
applied to a given volume of saw log harvest to esti-
mate trees removed in each diameter class. In turn,
this estimate can be related to an inventory stand
table in order to compute cutting rates.

SURVEY METHODS
AND RELIABILITY OF ESTIMATES

A basic need in the logging residue surveys was
to develop factors that could be applied to a re-
ported volume of saw log harvest to estimate the
resulting volume of logging residues. Estimates of
residue volume are based on product volume rather than
acreage logged because such information usually is more
reliable and available (at least to Forest Survey)
than are estimates of area cutover. The survey design
prescribed three basic types of measurements of grow-

ing stock trees on active logging operations to meet
this objective:

1. Net volume of saw logs harvested from
product trees measured on a logging
operation;

2. Net volume of residues from the same
trees;

3. Net volume of residues from other trees
cut or destroyed in, the process (or
felling and skidding product trees.

All three sets of measurements were used to
determine the residue volume as a percent of saw log
volume. Scaling was done in detail to permit esti-
mates of gross and net cubic-foot volumes for all
measured growing stock trees, and to provide gross
and net board-foot volumes to fixed and variable tops
for measured sawtimber trees. Species, diameter breast
height (d.b.h.), total height, overutilization (by.
Forest Survey standards), and cause of residue (fell-
ing or skidding) were recorded.

Table 3.--Growing stock trees removed from tnventory tn
saw log operations per 1 thousand cubie feet of
net product volume, Arizona and New Mextco

Db nwwelass: : : : arte S ;
Arizona .New Mexico .Arizona-New Mexico

(inches) :
------------ Number of trees-------------

2 AP G22A TSR 0149 41.8077

4 27.6987 20.8377 24.9676

6 6.5949 4.6189 5.8084

8 22215 1.7846 2.0476
10 1.1801 7348 1.0029
12 Silesy | .4199 O14
14 1.1454 b. 2597 1.1909
16 1.7008 7348 1.3163
18 1.9091 Mee2ia 1.7968
20 Dae oli 1.4697 9222
22 .9901 -9973 oes
24 1.3884 Leet 2Z 1). 5501
26 . 7983 6299 oS
28 .5901 F. LO2ZZ2 .7939
30+ 1.6314 2.0470 1.7968
All classes 97.8481 72.5907 87.7941

The number of basic sample units used in the
survey corresponded to the number of logging opera-
tions on which measurements were taken. Before start-
ing fieldwork in a State, an estimate was made of the
number of sample units needed to assure a standard
error of total residue volume of not more than +20
percent to mect foresie sunvieysObiyiectives.:, » Forgenc
survey reported here, 39 sample units--23 in Arizona
and 16 in New Mexico--were drawn from a list of known
active logging operations in the two States. These
were drawn at random from strata defined by land
ownership and operator size class. Two ownership
classes were used--National Forest and other owners.
Operator size class corresponded to the production
class of the sawmill for which the logging was being
done. Two size classes were used--small (less than
10 MMBF per year) and large (10 MMBF or more per year).

Enough trees were measured on each sample unit
to provide a product volume of between 4 to 10 MBF
per sample unit. On the basis of previous survey
experience, guides were developed so that field crews
could estimate the number of trees to be measured to
meet volume objectives. The number of trees varied
with the range in average tree size, timber type, and
stand age (young or old growth). From 10 to 30 trees
were recommended for each sample. Actually, 574 prod-
uct trees were used, an average of 15 per sample unit.
The net product volume scaled was 52,107 cubic feet
(equivalent to 328,269 board feet), an average of 8.4
MBF per sample unit.

Trees felled for products were measured in place
to determine both product and residue volumes. Resi-
due volume from other trees destroyed or cut when
product trees were felled also was measured. Skid-
ding damage to trees along skid trails was determined
after logs reached a landing, except in those cases
where crews had been on hand to witness damage as it
occurred.

In clear-cut operations where there was difficulty
in relating felling and skidding damage to individual

Table 4.--Standard errors of ratios for logging residue
volumes by net cubte- and board-foot! measures,
Artzona and New Mexico

_ rr

Area2
Unit of measurement : ; Arizona-
and > Arizona : New Mexico: New Mexico
minimum top diameter : G25)" 3: (16) : (39)
-~------------ Percent-----------
Cubic foot Seely 7al! 12975 9.347
4 inches
Board foot Zo ALS) 14.796 WI 5 WL
Variable
Board foot N64! TAPES 1ST.
7 inches

1Tnternational 1/4-inch rule.

*Number of logging operations sampled in parentheses.

product trees, a slightly different procedure was used...
In such cases, product trees were those whose stumps
wene Wichin a circular plot. All product trees on

the plot were measured, and felling and skidding

damage assessed within plot boundaries after skidding.

Data compilation was accomplished by means of a
set of computer programs developed especially for
these studies. The output included standard errors
of the ratios for residue volumes. For example, table
4 indicates that the standard error of the cubic-foot
Eatvo) in Ar_zona is 2135.2 percent,, and, im New Mexico,
is Un pereent..

Caution is recommended if estimates shown in this
report are to be applied to any subdivisions of Arizona
and New Mexico. The amount of residue per unit product
can vary widely from one area to another due to several
interrelated factors. Among these are: stand conditions
(saize, “and soundness. of trees, species, stocking, etc.) ;
markets for various species; size and quality of tim-
ber; and logging costs and techniques as determined
by accessibility, terrain, etc.

TERMINOLOGY

Cull trees.--Live trees of commercial species
that will not now or in the future qualify as saw-
timber trees because of dimensions, form, rot, or
damage. Also includes all live trees of noncommercial
species.

Cull volume.--Portions of a tree that are unusable
for industrial wood products because of rot, form,
or other defect.

Diameter classes.--A classification of trees
based on diameter breast height (d.b.h.) outside bark.
Two-inch diameter classes used by Forest Survey are
identified by the diameter at the approximate midpoint
of each class. For example, the 2-inch class includes
trees 1.0 to, 229 inches debeh-

Growing stock trees.--Live trees of commercial
speciesi; except those’ that are’ culd because of form,
rot, or other defect.

Growing stock volume.--Net volume in cubic feet
of growing stock trees 5.0 inches d.b.h. and over from
a 1-foot stump to a minimum 4.0-inch top diameter in-
Side bark (d.i.b:) of the central stem or to the point
where the central stem breaks into the limbs.

Logging restdues.--The unused portions of trees
cut or killed by logging.

Wet volume.--Gross volume less deductions for
rot, sweep, or other defects affecting use for timber
products.

Poletimber trees.--Growing stock trees likely to
grow into merchantable sawtimber trees. They must not
show evidence of rot in the main stem nor have serious
damage, crook, or stagnation. Softwoods must be from
5.0) tors. 9 inches d.b.h. and hardwoods from 5.0 to
10.9 anches: d2bihe

10

Sawttmber trees.--Growing stock trees containing
at least a 12-foot saw log and not more than two-
thirds of the gross board-foot volume in cull material.
Softwoods must be at least 9.0 inches d.b.h. and
hardwoods at least 11.0 inches d.b.h.

Sawtimber volume.--Net volume (in board feet
International 1/4-inch rule) of sawtimber trees be-
tween a 1-foot stump and a specified merchantable
top--fixedor/variable. A fixed top.is 7 inches in
diameter inside bark. A variable top varies with
d.b.h. as follows;

Range in d.bD.h. Tops dt...
Inches Inches
9-0 = 10.9 5

1. 07S 14.9 6
£50 = 189 7
19.0 - 20.9 8
2450 =. 24+9 9
25.0+ 10

1 |

AFLC/HAFB, Ogden

= te rae 8 : 24

SETZER, THEODORE S., ALVIN K. WILSON, and GROVER A. CHOATE

1970. Logging residues on saw log operations, Arizona and New
Mexico. USDA Forest Serv. Res. Pap. INT-78, 11 p.

A logging residues survey provided information on (1) factors to esti-
mate total removals from inventory, (2) residue volume in relation to
saw log volume, (3) importance of felling and skidding as causes of
residues, and (4) numbers of trees removed from inventory by logging.

7

SETZER, THEODORE S., ALVIN K. WILSON, and GROVER A. CHOATE

1970. Logging residues on saw log operations, Arizona and New
Mexico. USDA Forest Serv. Res. Pap. INT-78, 11 p.

A logging residues survey provided information on (1) factors to esti-
mate total removals from inventory, (2) residue volume in relation to
saw log volume, (3) importance of felling and skidding as causes of
residues, and (4) numbers of trees removed from inventory by logging.

a

Headquarters for the Intermountain Forest and
Range Experiment Station are in Ogden, Utah.
Field Research Work Units are maintained in:

Boise, Idaho

Bozeman, Montana (in cooperation with
Montana State University )

Logan, Utah (in cooperation with Utah
State University)

Missoula, Montana (in cooperation with
University of Montana)

Moscow, Idaho (in cooperation with the
University of Idaho)

Provo, Utah (in cooperation with Brigham
Young University )