Post-fire Recovery of
Wyoming Big Sagebrush
Shrub-steppe in Central and
Southeast Montana
Prepared for:
United States Department of the Interior
Bureau of Land Management
State Office
Prepared by:
Stephen V. Cooper, Peter Lesica and Gregory M. Kudray
Montana Natural Heritage Program
a cooperative program of the
Montana State Library and the University of Montana
December 2007
MONTANA
Natural Heritage
Program
Post-fire Recovery of
Wyoming Big Sagebrush
Shrub-steppe in Central and
Southeast Montana
Prepared for:
United States Department of the Interior
Bureau of Land Management
State Office
Agreement Number:
ESAO 10009 Task Order #29
Prepared by:
Stephen V. Cooper, Peter Lesica and Gregory M. Kudray
MONTANA
Natural Heritage
Program
^ t State r& 2^S2^L ~
^ Library %jm Montana
© 2007 Montana Natural Heritage Program
P.O. Box 201800 • 1515 East Sixth Avenue • Helena, MT 59620-1800 • 406-444-5354
This document should be cited as follows:
Stephen V. Cooper, Peter Lesica and Gregory M. Kudray. 2007. Post-fire Recovery of Wyoming
Big Sagebrush Shrub-steppe in Central and Southeast Montana. Report to the United States De-
partment of the Interior, Bureau of Land Management, State Office. Montana Natural Heritage
Program, Helena, Montana. 16 pp. plus appendices.
ii
Executive Su m m a r y
Sagebrush is a widespread habitat throughout
our study area and a number of species including
Greater Sage-grouse, pronghorn, Brewer's Spar-
row, Sage Sparrow, Sage Thrasher and sagebrush
vole are sagebrush dependent, at least at some stage
of their life cycles. Fire constitutes an important
driver in structuring sagebrush ecosystems; past
investigations have established that the response of
the big sagebrush component (Artemisia tridentata
Nutt.) varies according to subspecies. In an earlier
study in southwestern Montana we statistically
determined that recovery of mountain big sage-
brush (A. t. ssp. vaseyana [Rydb.] Beetle) cover
occurred in slightly more than 30 years, however
the minimal data for Wyoming big sagebrush (A.
t. ssp. wyomingensis Beetle & Young), indicated a
much longer recovery period (Lesica et al. 2005).
In this study we used the same sampling protocol
at 24 burned-unburned paired sites in central and
southeastern Montana where Wyoming Big Sage-
brush is the dominant big sagebrush taxon and the
accompanying flora is more closely allied with the
Great Plains than the Intermountain West.
Prescribed burns and wildfires typically result in
the complete mortality of Wyoming big sagebrush.
We found that Wyoming big sagebrush recovers
very slowly from both types of burns at all sites,
even those with relatively moist conditions. Full
recovery to pre -burn sagebrush canopy cover con-
ditions will take well over 100 years. The median
time since fire was 22 years and ranged from 4 to
67 years. We found no Wyoming big sagebrush
canopy cover recovery for 17 of the 24 sites after
burning had occurred and the oldest burn was only
8% recovered. Livestock grazing does not seem to
be casual as the only site without livestock grazing
for the entire period after burning had no canopy
recovery in 25 years. Burned plots were located
near unburned areas to ensure that a seed source
was relatively available since Wyoming big sage is
known to lack a soil seed bank.
Perennial and annual grass cover increased after
burning, however virtually all of the 11% increase
in annual grass is from field brome (Bromus ar-
vensis, formerly Japanese brome, Bromus japoni-
cus), regarded as a weed with negative habitat and
livestock value. Perennial grass cover increased
27% and 20% followed prescribed fire and wildfire,
respectively. Western wheatgrass (Pascopyrum
smithii) increased by 17% and accounted for most
of the perennial grass increase. These increases did
not decline with time since burning, which may
be explained by the lack of the competitive influ-
ence of sagebrush recovery. There was no change
after burning in overall forb cover or the numbers
of forbs of the Cichorieae Tribe of the Asteraceae
family. The Cichorieae tribe forbs are important
for successful Greater Sage-grouse brood rear-
ing. Plant species richness significantly declined
in burned plots compared to their unburned control
plots.
Our findings of extremely slow Wyoming big
sagebrush recovery after fire are similar to the other
research in the area (Eichhorn and Watts 1984) and
also supports findings by Baker (2007) that fire
rotations for this subspecies are about 100 - 240
years.
The slow Wyoming big sagebrush recovery and
the increase in the weedy annual grass field brome
suggests that managers concerned about Greater
Sage-grouse and other sage-dependent species
should be extremely cautious with prescribed burns
and wildfires in this region. Burns may essentially
eliminate sagebrush habitat, increase weedy annual
grass cover, reduce species richness, and could take
a century or more for recovery to pre -burn sage-
brush cover conditions.
in
Acknowledgements
We especially thank Nora Taylor of the BLM for
her generous support in making this project pos-
sible. Louise deMontigny and Eric Lepisto of the
Miles City Field Office, Bureau of Land Manage-
ment were instrumental in locating southeastern
Montana study sites, as was Jeff DiBendetto of the
Custer National Forest (Billings). Michael Stops,
Chief Ranger Little Bighorn Battlefield National
Monument, graciously permitted sampling at this
historical site. Larry Eichhorn (Lewistown, retired
BLM range conservationist) was generous with
his time, helping us relocate his original sagebrush
succession study sites and dispensing informed
commentary on the study. Tom Stivers of Montana
Fish, Wildlife and Parks shared his knowledge of
central Montana sage-steppe fire history crucial
to our locating several sampling sites. U. S. Fish
and Wildlife personnel at the Charles M. Russell
National Wildlife Refuge, especially Bill Berg,
Bob Skinner and Joann Dullum, provided loca-
tion information on past refuge fires. We thank the
several ranchers who granted access to their lands.
Our sincere appreciation to Lisa Wilson and David
Salazar who served as field assistants, admirably
discharging their duties and providing informed
camaraderie. Coburn Currier's suggestions con-
tributed to manuscript organization and readability
before he formatted it to MTNHP specifications.
IV
Table of Contents
Introduction 1
Study Area 2
Methods 4
Field Methods 4
Data Analysis 5
Results 5
Wyoming Big Sagebrush and Shrub Recovery 5
Herbaceous Recovery 7
Species Richness 8
Discussion 8
Sagebrush and Shrubs 8
Graminoids 9
Forbs 11
Management Implications 11
Conclusion 12
Literature Cited 13
Appendix A: Species List of Vascular Plants Occurring in Macroplots
Appendix B: Representative Photographs
List of Figures
Figure 1. Map of study area 3
Figure 2. Linear model between Wyoming big sage percent canopy recovery and
time since fire for 24 sites 6
Figure 3. Linear model between canopy height of dominant Wyoming big sage
cohort and time since fire for 24 sites 7
Figure 4. Second order function depicting canopy height of Wyoming big sage
dominant cohort since fire for 24 sites 7
List of Ta b l e s
Table 1. Demographic parameters for Wyoming big sage on burned and control plots 7
Introduction
Sagebrush steppe is a dominant vegetation type
in the Great Basin and Intermountain Region of
western North America but it is also important
in portions of the Northern Great Plains where
agriculture (cereal grains) and mixed-grass prairie
now dominate. Wyoming big sagebrush (Artemisia
tridentata ssp. wyomingensis) dominated
vegetation is an important component of the
semiarid landscapes east of the Rocky Mountains
stretching from Wyoming through Montana to
just south of the border with Canada; it is also
found in westernmost North Dakota. Throughout
southeast Montana Wyoming big sagebrush is
the only subspecies of A. tridentata present,
usually on fine textured soils; the only other large
shrubby sagebrush present in this region is silver
sagebrush (A. cana), found on drainage terraces
and sandy substrates. Physiognomy of Wyoming
big sagebrush stands in the Northern Great Plains
differs from the Intermountain Region in that the
undergrowth is dominated by rhizomatous grasses
as opposed to tussock-forming grasses. Also
influencing stand physiognomy are two notable
clines in Wyoming big sagebrush size presumed
to reflect available soil moisture; one of increasing
plant height from 1) south to north and 2) from
lower to higher elevation. Mountain big sagebrush
(A. t. ssp. vaseyana) is also found within the study
area to a limited extent; it occurs at lower treeline
and in mountain parklands of the isolated mountain
ranges of central Montana.
Fire was instrumental in structuring presettlement
sagebrush ecosystems, generating a mosaic of
stands of different size in various serai stages (West
2000). Fire, even of low intensity, does not thin or
lower sagebrush density by killing some fraction
of sagebrush plants throughout a stand, rather it is
stand-replacing because mortality is complete when
flames reach sagebrush (Baker 2007). Conserving
native species diversity likely requires maintaining
a comparable mosaic. Greater Sage-Grouse
(Centrocercus urophasianus), for example, require
barren habitats for leks, relatively dense stands
of medium height for nesting (Klebenow 1969,
Wallestad and Pyrah 1974, Aldridge and Brigham
2002), open stands for brood raising (Klebenow
1973, Wallestad 1971), and full-canopied tall
stands for wintering (Eng and Schladweiler 1972).
Greater Sage-Grouse populations apparently can
be constrained by the loss of any one of these
structural types (Connelly et al. 2000, Roscoe
2002). Antelope, Brewer's Sparrow, Sage Sparrow,
Sage Thrasher and sagebmsh vole are also
sagebrush dependent, at least at some stage of their
life cycles.
Management strategies that promote the
conservation of all sagebrush steppe-dependent
species are currently being formulated, and
prescribed fire has been proposed as a method
to control the density of big sagebrush stands
(Klebenow 1973; Pyle and Crawford 1996).
However, as post-fire succession proceeds from
immediate post-treatment to mature structure,
we only have limited knowledge of changes in
sagebrush cover, height, associated vegetation
and other characteristics. Though considered a
climax-dominant species, evidence suggests that
big sagebaish burning response varies according to
subspecies and may require many years for post-
fire re-establishment (Baker 2007). Wyoming big
sagebrush, although highly variable in response
(Walhof 1997, Wambolt et al. 2001, Watts and
Wambolt 1996), has almost no recovery for 30
years (Wambolt and Payne 1986, Eichhorn and
Watts 1984) and generally requires at least 50 years
to attain a density equal to that of the unburned
control (Baker 2007, Colket 2003). With the lone
exception of the Eichhorn and Watts (1984) study
in central Montana's Missouri River Breaks, none
of these studies were conducted in a Great Plains
environment. The ecological dynamics and habitat
characteristics of these sagebrush communities are
almost certainly strongly influenced by their age
(size) structure. Landscape scale comprehensive
management of sagebrush cannot be achieved
without understanding how structural and
compositional components change with time since
disturbance.
The purpose of this study was to describe and
substantiate the change in sagebrush and associated
vegetation after fire in the Northern Great Plains
of eastern and central Montana. We documented
changes in shrub height, cover and size-class
distribution by sampling numerous stands of
various post-fire ages and asked whether recovery
differed by ignition source (wildfires versus
prescribed burns).
Study Area
Sampling was conducted over a broad swath of
eastern Montana (Figure 1) from a westernmost
site within the Bighorn Basin Section, Bighorn
Intermountain Basin Subsection (342Ad, Bailey
1995, Nesser et al. 1997) to the eastern-most
Section-Subsection, Northwestern Great Plains,
Pierre Shale Plains (33 lFc). However, most of the
sampling occurred in the Northwestern Glaciated
Plains Section (within the Montana Glaciated
Plains [331Dh] and the Missouri River Breaks
[33 lDf] Subsections) and the Powder River Basin
Section (within the Montana Shale Plains [331Gb],
the Montana Sedimentary Plains [331Ge], and the
Powder River Basin/Breaks/Scoria Hills [331Gc].
All these units, with the exception of 342Ad,
occur within the Great Plains-Palouse Dry Steppe
Province (Bailey 1995).
Steppe and shrub-steppe vegetation is
characteristically associated with semi-arid climatic
regimes with an annual precipitation from 250
to 500 mm (10 - 20 inches). The mixed-grass
prairie and shrub-steppe results from the relatively
low annual precipitation, which according to the
DAYMET model (Thornton et al. 1997) varies
from 274 mm (10.8 in., vicinity of confluence of
Alkali Creek with Musselshell River) to 415 mm
(16.35 in., on high plateaus near Diamond Butte on
the Custer National Forest), a difference of about
50% compared to the lower value. Precipitation
patterns for the Baker, Bridger and Ekalaka stations
(Figure 1) indicate that the amount received in the
biologically critical spring quarter (April, May,
June) ranges from 44 to 47% of total precipitation.
These percentages are almost identical to the
spring percentage (and absolute amount) received
in southwestern Montana, where sagebrush also
predominates (Lesica et al. 2005). Due to the
distance from moderating oceanic influences,
another semi-arid climatic regime attribute is
strong seasonal (winter to summer) and diurnal
temperature fluctuations. The main climatic
difference between Wyoming big sagebrush
habitats in eastern Montana and in southwestern
Montana is the warmer summer daily maxima and
minima in eastern Montana, due primarily to lower
elevations. Eastern Montana study area elevations
ranged 270 to 1,220 m (890 to 3,990 ft.). Sampled
plots in Southwestern Montana sagebrush ranged
from 1,800 to 2,035 m (5,900 to 6,675 ft; Lesica
et al. 2005). Both regions reliably experience
convectional storms in July and August, but rainfall
is locally erratic within both areas.
Wyoming big sagebrush was the only big
sagebrush subspecies identified on sampling sites,
although the considerably larger silver sagebrush
was also encountered, especially on stream terraces
and sites having a greater percentage of sand
in the soil. In addition to being distinguished
by minor morphologic and chemotaxonomic
differences from silver sagebrush, Wyoming big
sagebrush also occurs on more xeric sites where
the annual precipitation ranges from 18 to 30 cm
(7-11 in.) (Winward 2004). Modeled study area
annual precipitation ranges from 274 mm (10.8
in.) to 415 mm (16.35 in.) (Thornton et al. 1997).
This apparent range extension of Wyoming big
sagebrush in terms of precipitation values may
be explained by its occupying higher elevation
sites in southeastern Montana, a region beyond
the established geographic range of mountain
big sagebrush. These extremes in precipitation
combine with other site differences, such as
elevation (an indirect measure of precipitation and
evapotranspiration), slope, aspect, and soil texture
(as measure of available water capacity) to explain
the range in mature plant height, 35 to 105 cm,
and the diversity of plant associations noted across
sampling sites.
The plant association associated with the driest
sites (mostly due to their very well drained
soils) was Wyoming big sagebrush / bluebunch
wheatgrass (Pseudoroegneria spicata). The most
mesic sites are characterized by Wyoming big
sagebrush / Idaho fescue (Festuca idahoensis)
- western wheatgrass (Pascopyrum smithii): these
sites were found on the relatively high elevation
butte tops of the Custer National Forest where
average annual precipitation exceeds 400 mm
(16 in.). The most commonly encountered plant
association was Wyoming big sagebrush / western
wheatgrass - green needlegrass (Nassella viridula).
Other plant associations are permutations of this
type created by site conditions (predominantly
related to soil texture) and disturbance regimes.
These include Wyoming big sagebrush / western
wheatgrass - Sandberg"s bluegrass (Poa secunda),
Wyoming big sagebrush / western wheatgrass
- blue grama {Bouteloua gracilis), Wyoming big
sagebrush / western wheatgrass - needle-and-
thread (Hesperostipa comata), and Wyoming big
sagebrush / western wheatgrass.
Methods
Field Methods
In June and July of 2006 and 2007 we sampled
24 sites dominated by Wyoming big sagebrush
in central and southeastern Montana within Big
Horn, Carbon, Carter, Custer, Garfield, McCone,
Petroleum, Phillips, Powder River, Rosebud and
Yellowstone Counties. We used lists of potential
sites provided by the Miles City Office of the
Bureau of Land Management (BLM), the Ashland
Ranger District of the Custer National Forest, and
personal communication to select sampling sites
based on age of burn and accessibility. Larry
Eichhorn, retired BLM range conservationist from
Lewistown, provided information valuable in
relocating the original sample sites of his study of
post-fire succession in central Montana (Eichhorn
& Watts 1984). We focused on federally or state
owned lands but did find several cooperative
private landowners.
At each site a macroplot (20 m by 50 m, 1000
m 2 ) was visually selected to represent prevailing
conditions within the burned area. A control
sample macroplot was established in unburned
sagebrush-dominated vegetation as close as
possible to the burn. The control was chosen to be
as similar as possible to the abiotic setting (slope,
aspect, soils) of the burned sample plot. Although
the unburned control macroplots are not true
controls because of not being randomly assigned
prior the fires, nonetheless they function as controls
by exemplifying what the burned plot probably
would constitute, had they not burned. With one
exception, burned macroplots were located within
20 m or less of the unburned control and always
in the same grazing pasture (not separated by
fencing). We noted the positions offence lines
and water developments and attempted to locate
sampling points as far removed as possible to
ensure that grazing pressure was not excessive.
However, we had no way of accurately accounting
for grazing regimes.
We used the Daubenmire (1959) concept of canopy
cover to estimate this parameter along five evenly-
spaced, parallel 20 m transects originating at the
50 m macroplot baseline (Mueller-Dombois and
Ellenberg 1974). At the 5 and 10 m marks of the
five transect lines 3 m 2 circular microplots were
established for determining rooted density for all
shrub species by four size classes: 1) seedlings,
height < 10 cm; 2) juveniles, height > 10 cm and
stem diameter at ground level < 1 cm; 3) sub-
adults, stem 1-3 cm diameter and 4) adults, > 3 cm
stem diameter. At alternate microplots (total of
five microplots) age and height were recorded for
one sagebmsh plant of each size class; we focused
on specimens exhibiting the least crown damage.
Sagebrush plants were cut with a fine-blade saw
or sharp pruning shears at ground level (which
sometimes required removing accumulated detritus
from around mature stems). Annual growth rings
were field counted with a 10X or 20X hand lens
(Ferguson 1964). To ensure that we had at least
three estimates for each size class it was necessary
to sample sagebrush plants outside the microplots,
however, complications to this approach arose due
to a tendency for even-aged stands and damaged
or rotted stems where we could not reasonably
approximate age. Study area Wyoming big
sagebrush plants tended toward a deliquescent
form (especially sub-adult and adult classes). This
tendency combined with mechanical damage from
grazers (presumably domestic stock) results in
stems lacking the pith and some number of annual
rings. We frequently experienced stands where all
sub-adult and adult specimens, or at least the 10
to 20 specimens we cut, were incapable of being
accurately aged and the smaller size classes had
significant stem damage as well.
In these same ten microplots we estimated the
percent canopy cover (Daubenmire 1959) of all
vascular plant species and ground cover types
(bare soil, gravel, rocks, litter, lichens, mosses,
basal vegetation) using 13 cover classes (T- = >0,
<0.1; T = >0.1, <1; P = >1, <5; 1 = >5, <15; 2 =
>15, <25, 3 = >25, <35; 4 = >35, <45; 5 = >45,
<55; 6 = >55, <65; 7 = >65, <75; 8 = >75, <85;
9 = >85, <95; F = >95, <100%). Also recorded
was the number of occurrences of each species of
the Cichorieae tribe of the Asteraceae in all ten
microplots.
The only burn information recorded was ignition
source, either wildfire or prescribed burn, and
the year of occurrence. Attempts to characterize
fire severity, a potentially significant explanatory
variable, were difficult because 1) immediate
post-fire conditions were not generally recorded,
and 2) quite a number of the burn ages were old
enough (20+ years) that significant clues had been
obscured. Fires presumed to be of high-intensity
consumed all, or nearly all of the sagebrush stems,
leaving only 2-5 cm projecting above the ground
and, in the most extreme cases, created a concave
stem obscured by surface materials. For two
sites the only evidence of fire was very scattered
charred branch remains and an obvious fire-line;
no stumps could be located. Both wildfires and
prescribed fires resulted in fire effects categorized
as high-severity. Fires of presumed lesser intensity
resulted in standing sagebrush main stems with
secondary and tertiary branches intact, but charred.
Examination of larger burns commonly revealed
multiple burn severity levels (so far as we were
able to detect these effects given the long time
since burning). Several sampling sites contained a
few Wyoming big sagebrush specimens that gave
the appearance of having escaped burning; only
one specimen was reliably aged and removed from
the recovery figures, the rest were counted as part
of the recovered cohort when sampling procedures
encountered them (aging indicated they had
established post-burn).
Data Analysis
Our main emphasis was to describe Wyoming
big sagebrush recovery, which we characterize
as percentage recovery and is calculated by
using the mean canopy cover or height of this
subspecies for the burned macroplot divided by
values from the unburned control macroplot. We
evaluated changes in stand height by using the
size class with the greatest canopy cover. Rate
of recovery for sagebrush is calculated as the
percent recovery for either canopy cover or height
divided by the number of years since burning. A
planned demographic analysis was frustrated by
our inability to accurately age stems, except those
of the seedling size class. Species richness is
measured by the number of vascular plant species
recorded in the 5 line intercepts (shrubs only) and
ten microplots (total of 30 m2).
The relative aridity of a site, as measured by
precipitation and potential evapotranspiration,
was hypothesized to affect recruitment and
other aspects of stand recovery. Slope and
aspect are the primary determinants of potential
evapotranspiration; these two variables along with
latitude have been integrated into a "heat loading"
index by McCune and Keon (2002). Average site
annual precipitation was estimated by DAYMET
a statistical model that integrates elevation, other
aspects of local terrain, and geographic position
with weather station data for the past 20 years
(Thornton et al. 1997).
We used paired-sample t-tests to evaluate the
differences between burned and unburned control
macroplots for Wyoming big sagebrush canopy
cover and height, total shrub cover and cover of
perennial grasses, annual grasses and forbs. Linear
regression analysis was used to model the recovery
of sagebrush height, sagebrush canopy cover and
herbaceous cover with time since fire. When
modeling sagebrush recovery regression lines
were forced through the origin to reflect biological
realities. Regression analysis was also used to test
the association between recovery rate of sagebrush
and the abiotic site factors of precipitation, heat
load index and soil texture.
Results
Wyoming Big Sagebrush and
Shrub Recovery
The sampled sites span a wide range of sites in
terms of water stress and hence composition. A
50% difference in annual precipitation, 10.8 to 16.3
cm, across the range of sites is probably the major
driver of compositional and canopy cover values.
The comparatively minor difference in heat load
index, 12%, between the most "extreme" sites in
our dataset is to be expected in these rolling plains
where the steepest slope was only 11%. Assuming
the kind and amount of undergrowth vegetation
is indicative, then the driest sites dominated by
bluebunch wheatgrass (averaging 28% cover
of perennial grasses with a range of 22 to 35%,
Appendix B) can be contrasted with the high-
elevation sites dominated by Idaho fescue and
western wheatgrass (74% average canopy cover
perennial grasses, ranging from 68 to 80%). The
remainder of the control plots did not always fall
between these extremes of perennial grass cover,
probably because of grazing effects (both sampling
year and long-term). Values lower than those
listed for bluebunch wheatgrass-dominated control
plots were registered for a number of control plots
having western wheatgrass dominant in several
different plant associations.
There was a median time since fire of 22 ± 16
(16 = 1 std. dev) years, ranging from 4 to 67
years for the 24 paired macroplots (control and
burned) we sampled. Fire resulted in a virtually
complete loss of shrub canopy cover as revealed
by examination of recently burned macroplots (<10
years, N = 6); five of the six plots had no shrub
canopy cover and one had < 2%. Wyoming big
sagebrush is the dominant shrub on the control
macroplots with an average cover of 20 ± 8%;
total shrub cover averages only slightly more, 21
± 8%, with the additional species including silver
sage, rubber rabbitbrush (Ericameria nauseousa),
green rabbitbrush (Chrysothamnus viscidiflorus),
and spineless horsebrush (Tetradymia canescens).
Silver sage is the only shrub even approaching
Wyoming big sagebrush in cover and that occurred
on only one site. The average height of the
dominant cohort of Wyoming big sagebrush in
control plots was 6 1± 11 cm.
Because there were only five prescribed burn
sites and four of these showed no recovery in
Wyoming big sagebrush cover (or total shrub
cover) we did not stratify the dataset according to
mode of ignition. For the recovery of Wyoming
big sagebrush canopy cover a linear model
(Figure 2) resulted in the best fit with age since
fire explaining 29% of the variation in cover (t =
2.81, P = 0.010). For total shrub cover recovery
results were not much different with a linear model
explaining only 22% of the variation (t = 2.38, P =
0.027). The mean recovery rate for Wyoming big
sagebrush canopy cover was 0. 16% / year ± 0.45;
projecting this rate results in a predicted 100%
Si
E
.a
OS
30 40 SO
Years since fire
Figure 2. Linear model between Wyoming big sage percent
canopy recovery and time since fire for 24 sites (both
prescribed and wildfire); regression model constrained to pass
through the origin.
recovery requiring an average of 625 years. Height
recovery of the dominant Wyoming big sagebrush
cohort was best fit by a highly significant (t =
4.81, P = <0.001) second order function (Figure
3) in which time since fire explained 55% of the
variation and the extrapolated time of recovery is
approximately 68 years. We also present a linear
model for comparison (Figure 4) that explains 54%
of the variation and is highly significant (t = 4.83,
P = <0.001), but which yields an intercept of more
than 80 years for complete height recovery, a result
inconsistent with biological realities.
A linear regression model incorporating the heat
load index and mean annual site precipitation
explained 30% of the variation in the rate of
Wyoming big sagebrush canopy recovery.
However, neither annual precipitation (P = 0.827)
nor the heat index load (P = 0.54) alone were
significantly related to canopy recovery rate.
— ■
3 20
Years since fire
Figure 3. A second order function depicting canopy height
of Wyoming big sage dominant cohort since fire for 24 sites;
regression model constrained to pass through the origin.
30 40 50
Years since fire
Figure 4. Linear model between canopy height of dominant
Wyoming big sage cohort and time since fire for 24 sites
(prescribed and wildfire); regression model constrained to
pass through the origin.
Although we were unable to acquire accurate ages,
regardless of specimen maturity /size class, Table
1 presents our best estimates of age as well as
density and height by maturity class. The density
(# of stems / m 2 ) of Wyoming big sagebmsh is
highly variable across all size classes in both burn
and control macroplots. The average density of
burned macroplots as a percentage of control plots
ranges from 25% for seedlings to 1% for the adult
class. The adult class dominates the structure for
the control plots but the variation in structure is
considerable. For burned macroplots no one class
is dominant. Obscured in Table 1 by the averaging
process is the fact that of the 24 burned macroplots
the seedling class was represented in only 4
macroplots, the juvenile class in 5 macroplots, the
subadult class in 6 macroplots, and the adult class
in 4 macroplots.
Herbaceous Recovery
The important perennial graminoids in order of
declining constancy were western wheatgrass,
Sandberg's bluegrass, blue grama, prairie junegrass
(Koeleria macrantha), green needlegrass, needle-
and-thread, bluebunch wheatgrass and sun sedge
(Carex inops ssp. heliophila). The mean perennial
grass canopy cover on control macroplots was
40%, approximately half was western wheatgrass.
The burned macroplots had an average of 61%
perennial grass cover, 39% of that cover is western
wheatgrass. The difference in perennial grass
cover was highly significant (t = 4.83, P <0.001),
but the time since fire is insignificant (t = 1.29, P =
0. 179) in explaining the difference.
The annual grass component, with an average
cover of 19% and 9% in burned and control
macroplots respectively, is comprised primarily
of the introduced brome grasses (field brome,
formerly Japanese brome) and cheatgrass (Bromus
tectorum). However, the native sixweeks fescue
(Vulpia octoflora, formerly Festuca octoflora)
also has appreciable constancy, although its cover
is negligible. The difference in annual grass
Table 1. Demographic parameters for Wyoming big sage on burned and control plots; averages and ranges by four size/maturity
classes.
Size/maturity classes
Seedling
Juvenile
Sub-adult
Adult
Burn versus
Control Plots
Number/ in2
(range)
Height
(em)
Average Age
(Range)
Number/ m2
(range)
Height
(em)
Average Age
(Range)
Number/ m2
(range)
Height
(em)
Average Age
(Range)
Number/ m2
(range)
Height
(em)
Average Age
(Range)
Burn plots
0.03
6±2
2.6
0.01
19 ±8
7.0
003
33 ±6
18.6
0.01
51 ±7
27.5
(0 to 0.27)
(2 to 3)
(0 to 0.06)
(4 to 9)
(0 to 0.13)
(12 to 25)
(0 to 0.06)
(28 to 35)
Control Plots
0.12
5±2
6.1
0.24
17±3
10.0
0.52
36 ±8
19.3
0.64
62 ±12
35.9
(0 to 63)
(2 to 13)
(0 to 0.S3)
(4 to 18)
(Oto 1.43)
(8 to 45)
(0.23 to 1.27)
(18 to 71)
cover between burned and control macroplots is
significant (t = 2.818, P = 0.010), but the difference
cannot be significantly attributed to time since
burning (t= 1.038, P = 0.311).
For forbs, there was no statistical difference (t =
0. 132, P = 0.896) in average canopy cover between
burned (8.3%) and control (8.0%) macroplots.
Forb canopy cover was less than graminoid cover,
but it did range as high as 27% due to an unusual
post-fire increase in the non-native corn speedwell
(Veronica arvensis) on one productive high-
elevation site. The most common forbs are the
non-natives pale madwort (Alyssum alyssoides),
field cottonrose (Logfia arvensis, formerly Filago
arvensis), herb sophia (Descurainia sophia),
littlepod false flax (Camelina microcarpa), yellow
salsify (Tragopogon dubius), common dandelion
(Taraxacum officinale), and the natives woolly
plantain (Plantago patagonica), tiny trumpet
(Collomia linearis), rough false pennyroyal
(Hedeoma hispida), spiny phlox (Phlox hoodii) and
American vetch (Vicia americana).
The most commonly occurring forbs of the
Cichorieae tribe were the non-natives common
dandelion and yellow salsify. The natives weevil
prairie-dandelion (Nothocalais troximoides) and
pale agoseris (Agoseris glauca) were found in
only one and two plot pairs, respectively. Due to
their extremely low densities native species were
lumped with non-natives for analysis. The mean
density of members of the Cichorieae tribe was
1.8 ±2.8 plants / m 2 for the burned macroplots and
1.3 ± 1.8 plants / m 2 for the unburned controls; this
difference was not significant (N = 24, t = 0.448, P
= 0.659).
Species Richness
The average number of species per macroplot,
species richness, had a mean value of 32 ± 6 for
control plots and 26 ± 7 for burned plots. Extreme
values ranged from 19 to 44 and 12 to 40 for
control and burned plots, respectively. There was
a significant difference in species richness between
burned and control macroplots (t = 3.737, P =
0.001), however this difference was not associated
with time since burning (t = 0.588, P =0.563).
Discussion
Sagebrush and Shrubs
Observation of both recently burned stands and
those of considerable post-burn age (> 20 years)
indicate that Wyoming big sagebrush mortality was
virtually complete. There was no measured canopy
recovery for Wyoming big sagebrush in 17 of the
24 sites. Our linear model of canopy recovery
is based on 24 sample pairs and the indicated
recovery rate is exceedingly slow. The highest
recovery rate in our study, 0.72 % / year (27%
recovery in 37 years), still implies full recovery
would require much more than 100 years given the
linear model. The oldest burn, 67 years, was only
8% recovered and recovery on the most moisture-
stressed sites as well as sites with the greatest
precipitation and most mesophytic vegetation
composition registered no recovery within 14
years. Even on an older (27 years), and ostensibly
cooler prescribed burn, recovery was only 3%.
The only site (Little Bighorn Battlefield National
Monument) without domestic stock use within the
recovery period (and for a considerable period prior
to burning) recorded no shrub canopy recovery in
25 years.
In the only other study within our sampling
area, Eichhorn and Watts (1984) found no re-
establishment of Wyoming big sagebrush in the
14 years following wildfire in the Missouri River
Breaks and vicinity. In southwestern Montana,
Wambolt et al. (2001) reported a 72% recovery
of Wyoming big sagebrush after 32 years in one
burn and 96% recovery after only nine years in
another. Watt and Wambolt (1996) documented
76% recovery within 30 years in another
southwestern Montana study. It should be noted
these southwestern Montana studies documented
cool-season, prescribed fires. Also in southwestern
Montana, Lesica et al. (2005) documented almost
no Wyoming Big Sagebrush canopy recovery
in six wildfire burn plots, the most being 3% in
23 years. In southeastern Idaho, Colket (2003)
found, measuring density not cover, that 3 of 17
plots attained full recovery in 53 years and that by
92 years 16 of the 17 plots reached full density.
Attaining full density is not equivalent to recovery
of canopy cover, which undoubtedly would require
additional decades for shrubs to mature (Baker
2007).
A nearby seed source is generally regarded as
promoting faster stand recovery (Blaisdell 1953,
Gruell 1980) because the seed bank of A. tridentata
is negligible to non-existent (Young and Evans
1989, Akinsoji 1988). For these reasons we located
the burn sample plots as close as practicable to
control plots, the ostensible seed source. This
strategy apparently made no difference, similar to
the results of Wambolt and Payne (1986) in their
prescribed burn study where the close proximity
of seed source still resulted in no Wyoming big
sagebrush re-establishment six years post-burn.
We hypothesized that stands on areas of higher
precipitation and/or with a lower heat load index
would have a higher rate of recovery, similar to
results from Johnson and Payne (1968). However,
we were unable to detect any biotic or abiotic
variables associated with Wyoming big sagebrush
recovery across our study area. A model with
age since fire, heat load index and precipitation
explained 30% of the variation in canopy recovery,
however, almost all of this explained variation was
attributable to using age as a covariate.
The average height of the dominant Wyoming big
sagebrush cohort in control plots is 61 ± 11 cm,
which agrees well with our southwestern Montana
(Lesica et al. 2005) measures of this subspecies
(61 ± 6 cm). Only 4 of 24 burned macroplots
even had a mature size/age class represented and
the average height was 50 ± 6 cm; one burned
macroplot attained full height recovery in 38 years.
Removing the zero values for height recovery
from Figure 3 would obviously shorten the time
expected for full recovery and would more closely
model what would be expected in the rate of height
growth of individual plants once established on a
site. However, for the model to be realistic on a
stand basis the zero values should be included.
The results of the demographic portion of this
study are disappointing due to equivocal aging
of the sagebrush. The poor condition (loss of
innermost annual rings, misshapen crowns) of
sagebrush stems spanned all age/size classes, but
defects were especially pronounced in the adult
class. More than 80% of burned macroplots lack
any representation of a seedling class. Seedling
production was virtually nil, even in 2007, a
year with abundant spring moisture that should
have favored at least seedling germination, if not
survival. We questioned this lack of seedlings
as perhaps anomalous and a consequence of
inadequate sampling. Therefore, in addition
to visually examining the 10 microplots, we
conducted extensive searches of adjacent terrain
and uniformly failed to detect seedlings there as
well. In general, the control macroplots had all
maturity classes represented, however more than
50% of the stands did not have a seedling class
present. The considerable difficulty Wyoming big
sagebrush exhibits in site recolonization might be
expected given that it occupies the driest sites with
the most poorly developed soils (Morris et al. 1976,
Barker and McKell 1983).
With the exception of the mostly missing seedling
class, nearly all the unburned control plots were
uneven-aged (had multiple size/maturity classes
represented), revealing recruitment is not limited
to immediate post-fire circumstances. Three
control plots were somewhat anomalous in that
only an adult class was present. Two of these three
plots had approximate stem ages indicating that
there had been no recruitment in more than 25
and 40 years. Although the adult class of these
two stands was not even-aged, their age structure
suggests episodic reproduction at some point in
time. Two of these three stands were noted to have
considerable Wyoming big sagebrush mortality
of undetermined cause (visually perceived to be
greater than noted for other sample stands).
Graminoids
The highly significant 21% increase in perennial
grass cover shows no diminution with time since
fire, which is understandable given that Wyoming
big sagebrush cover exhibits hardly any recovery,
even after more than 60 years. This response can
be contrasted with perennial grass cover in burned
stands once dominated by mountain big sagebrush
in southwestern Montana where there was a modest
7% increase in perennial grasses (Lesica et al.
2005). However, this effect was not detectable
after about 25 years, about a decade preceding full
sagebrush canopy recovery (Lesica et al. 2005).
Possibly even greater increases in annual grass
cover may have been negated by post-fire livestock
grazing when the grass becomes more accessible
after shrub canopy elimination (Pechanec et al.
1954, Harniss and Murray 1973, Bunting et al.
1998). In our unburned control plots perennial
grass cover, an index of long-term grazing
intensity, was not associated with proportional
changes in grass cover following fire. This implies
that post-fire grazing has not had a large impact on
fire-induced changes.
The major contributor to the significant increase
in post-fire perennial grass cover appears to be
the rhizomatous western wheatgrass with a highly
significant (N = 23, P = 0.001) 17% difference
(39 vs 22%) in cover (77% increase). The other
important rhizomatous graminoid, blue grama,
exhibited 10% average canopy cover on burn plots
and only 4% on controls, but due to high variability
this difference is not significant at the 5% level (N
= 22, P = 0.085).
The species richness of bunch-forming graminoids
is greater than that of the rhizomatous component,
although their combined canopy cover is less
in burned (12%) and control (14%) macroplots.
Sandberg's bluegrass is highly constant but
insignificant in cover, both in burned (1.4%)
and control (1.3%) macroplots, and shows no
significant response to burning (N = 24, P = 0.752).
In several stands green needlegrass registered a
large post-fire cover increase, but overall there
was no significant effect (N = 18, P = 0. 155). The
5% average canopy cover of needle-and-thread
in both control and burned macroplots reflects no
significant difference (N = 16, P = 0.915), but there
were both notable six-fold increases and a fifty-fold
decrease. Bluebunch wheatgrass, a relatively less
important grass in the study area (45% constancy),
gives the deceptive impression of decreasing
canopy cover with burning (2% vs. 5%), but in
at least one instance cover notably increased,
resulting in overall statistical insignificance (P =
0.345). This inconsistent bluebunch wheatgrass
response with burning reflects results found in the
literature with increases (Wambolt and Payne 1986,
Humphrey 1984), decreases (West and Hassan
1985) and no change (Peek et al. 1979, Antos et al.
1983) recorded. The lumping of prescribed with
wildfire responses in our test may have resulted
in a seeming lack of bluebunch wheatgrass cover
association with fire. For example, to the west
of the Musselshell River's confluence with Ft.
Peck Reservoir on the 1996 Alkali Creek Burn,
a wildfire of presumed high-intensity nearly
extirpated bluebunch wheatgrass (decreasing to
0.25% from the 29% canopy cover on the control).
Emphasizing the uniqueness of fire response is the
observation that on the same plot pair blue grama
cover increased dramatically (control 2%; burned
52%), presumably as a result of fire.
Idaho fescue is an important grass in eastern
Montana only on high-elevation sites. On our two
sites, both with prescribed fires, it both increased
dramatically (47 to 69%) and decreased (38 to
23%) 14 and 15 years post-fire, respectively. In
southwestern Montana there was no statistical
difference in Idaho fescue cover between burned
and control macroplots (Lesica et al. 2005),
although it has been reported that this species is
damaged by fire, at least in the short-term, due to
the foliar density of tussocks (Wright et al. 1979).
The average annual grass canopy cover for both
burned (19%) and control (9%) macroplots is
comprised almost entirely of the non-native field
or Japanese brome, which has a highly significant
cover increase following fire (N = 23, P = 0.010),
and no significant diminution of cover with time
since fire. Its cover ranges from zero to 69% in
burned plots. Field brome is usually regarded
as a weed on rangelands and prairies because it
competes with native perennials for water and
nutrients (Stubbendieck et al. 1985, Gartner et
al. 1976). Fire is noted (Gartner et al. 1986,
Whisenant 1990) to reduce field brome population
density for one or two years post-burn primarily
as a consequence of litter reduction (critical
for seed germination and establishment). We
found no research that followed the post-burn
course of succession for more than two years.
We hypothesize that the observed field brome
response was due to exploitation of space, water
10
and nutrients following sagebrush mortality and
consequent loss of competition.
Forbs
Our results suggest that forbs are generally well-
adapted to these fire-prone communities because
no statistical difference was demonstrated (t = .132,
P = 0.896) between burn (8%) and control (8%)
macroplot forb cover. However, we did have plots
where forb cover decreased or increased drastically,
usually due to the cover of one or two species. For
example, on both the youngest (4 years) and oldest
(67 years) burns lesser spikemoss (Selaginella
densa) was totally killed and reduced to 2% cover
contrasted with 41% and 22% cover, respectively,
on the control macroplots. On two plot pairs a
positive response to burning was displayed by
the annual non-natives field cottonrose (<1% to
24%) and corn speedwell (<1% to 23%). The
rather stochastic nature of these responses is
emphasized by the fact that field cottonrose cover
was minor (1.5%) in the burned macroplot where
corn speedwell cover was so high. It is noteworthy
that these large differences in forb cover are due
to annuals, not to native perennials, which register
hardly any change. Similar results have been
reported for prescribed burns in sagebrush steppe
by Peek et al. (1979), who found forb frequency
was not affected three years post-burn, and also
by the Harniss and Murray (1973) report of stable
forb cover for 30 years following fire in eastern
Idaho. Wildfire did not produce any change in
canopy cover of forbs in south-central or southwest
Montana (Hoffman 1996, Fraas et al. 1992).
Forbs of the Cichorieae Tribe of the Asteraceae
Family have been determined to comprise an
important component of Greater Sage-Grouse
summer diet and are often crucial for successful
brood rearing (Klebenow and Gray 1967,
Peterson 1970, Barnett and Crawford 1944,
Drut et al. 1994). An increase in forbs can be
expected with the fire-induced reduction in the
cover of shrubs and grasses (Klebenow 1973,
Glenn-Lewin et al. 1990). We combined the
relatively rare occurrences (<40 plants / 1,440
m 2 ) of native Cichorieae weevil prairie -dandelion
and pale agoseris with the much more abundant
non-native Cichorieae densities, but found no
evidence for a fire-driven change. Lesica et al.
(2005) also found no change with fire for non-
native Cichorieae in southwest Montana (2.7 ± 0.9
plants / m 2 , burned macroplots: 2.0 ± 0.6 plants
/ m2, control plots). Comparable figures for our
study area are 1.6 ± 2.7 plants / m 2 (burned) and
1.3 ± 1.8 plants / m 2 (control), which indicates
that study area Cichorieae densities are less than
those of southwestern Montana and considerably
more variable site to site. A high degree of within
site variation in density was also noted, but not
statistically tested. Since non-native Cichorieae are
invasive and increase with disturbance (Hobbs and
Huenneke 1992, Kotanen et al. 1998) their lack of
response was unexpected.
Management Implications
Most research from outside our study area,
documents a highly variable response of Wyoming
big sagebrush to prescribed burning and a variable
response of longer recovery periods for wildfire.
Our data from central and southeastern Montana
suggest that recovery (attaining 100% canopy
cover of control) will require much more than 100
years. We had no rapid Wyoming big sagebrush
recovery within the study area. The only other data
within our study area (Eichhorn and Watts 1984)
indicated no Wyoming big sagebrush recovery in
14 years and is corroborated by our study showing
that even our oldest prescribed burn, which also
occurred on a mesic site, had only 3% recovery in
27 years. The response to wildfire may be even
slower with two of our sites showing no recovery
23 and 25 years following burning, and our oldest
sites had only 6 to 17% recovery after > 50 years.
The average Wyoming big sagebrush canopy
recovery rate of 0. 16 ± 0.44% / year implies
full recovery is attained in > 600 years which is
biologically improbable because as demonstrated
by Lesica et al. (2005, who had data-points from
the complete time-line including full recovery) a
non-linear model is the best fit. Although Lesica
et al. (2005) documented mountain big sagebrush
recovery, we presume the model expression would
be similar for Wyoming big sagebrush with only
a greater time to full recovery, certainly less than
600 years. In interpreting our results it should be
noted that our close placement (<20 m) of burn
11
macroplots to control plots should speed recovery
due to local seed source proximity. An example
of differential recovery with distance from seed
source is detailed by Welch and Criddle (2003).
Mountain big sagebrush canopy recovery takes
about 35 years, but to merely reach the interior of
a burn in Idaho required 70 years or more (Welch
and Criddle 2003). The time to fully recover an
extensive Wyoming big sagebmsh burn could be
very considerable.
The three stands with only an adult size class
present might be considered as evidence supporting
the contention that sagebrush steppe is a fire-
dependent vegetation type requiring periodic
renewal by fire (Winward 1991). Overall the size
class structure of our stands argues for a steady-
state structure and a lack of fire dependence as
suggested by Connelly et al. (2000) and Welch
and Criddle (2003). Our results support the
observation that, although fire is an important
natural disturbance in sagebrush steppe, it could
not have occurred as often as suggested in the past
(see Baker 2007 for a review). Our results support
Baker's (2007) interpretation indicating that fire
rotations are about 100 - 240 years for Wyoming
big sagebrush and that sagebrush steppe belongs to
fire regime V (long rotation, stand replacement).
None of the factors (soil texture, precipitation,
slope, aspect [we combined slope and aspect
into a heat load index]) that have been cited as
influencing sagebrush recovery (Johnson and
Payne 1968, Gruell 1980) were associated with
the rate of canopy recovery in our study. Thus,
managers cannot presume that stands of Wyoming
big sagebrush on more mesic sites will exhibit
faster recovery, or that prescribed fire, as compared
to wildfire, will result in more rapid recovery.
Our results are pertinent to protecting native
biological diversity and managing domestic
stock within the study area sagebrush steppe. An
average increase in perennial grass cover of 27%
and 20% followed prescribed fire and wildfire,
respectively. We have no evidence that this
amplified cover will be diminished until sagebaish
canopy cover becomes substantial at some future
time, probably at least a century after burning.
Greater Sage-Grouse will find this augmented
perennial grass cover beneficial (Wallestad and
Pyrah 1974, Aldridge and Brigham 2002) as will
domestic stock, which also benefit from increased
accessibility to the herbaceous component due
to shrub canopy removal. The 11% increase in
annual grasses is due almost wholly to field brome
which is considered by some a noxious weed
(Stubbendieck et al. 1985) because it competes
with native perennials for water and nutrients
and has a brief window of grazing availability
as it rapidly matures and loses nutrient content,
digestibility and palatability (Stubbendieck et al.
1985). Although various studies (see Stubbendieck
et al. 1985) indicate it declines with time on a site
we have no indication this is the case. Burning
sagebrush stands infested with field brome may
result in a long-term increase in this undesirable
species.
Success of Greater Sage-Grouse brood rearing is
dependent on available forbs, especially those of
the Cichorieae, both native and exotic (Connelly et
al. 2000). We found no predictable increase in forb
cover, including those of the Cichorieae, with fire.
At some sites we did find a large increase in exotic
annual forbs, presumably they consume water and
nutrients better directed to perennial natives and
they appear unpalatable to domestic stock as well.
Managers concerned about declining populations
of Greater Sage-Grouse and some other sage-
dependent species should be aware of the Wyoming
big sagebrush response after fire in our study
area. Greater Sage-Grouse are dependent on some
mixture of open- and closed-canopy sagebrush
habitats to complete their life cycle (Connelly et al.
2000). Wyoming big sagebrush recovery takes so
long that managers considering prescriptive burns
need to have a long-term view of the landscape
before eliminating a sagebrush habitat that will
not return for at least a century. Similar concerns
may be expressed about wildfire management in
sagebrush habitats.
Conclusion
Wyoming big sagebrush recovery from prescribed
fire and wildfire was extremely slow in our
12
eastern Montana study area and likely requires
well over 100 years to reach pre-burn sagebrush
cover conditions. Results were similar across all
environmental conditions, even at relatively mesic
sites. Perennial and annual grass cover increased
after burning, but the annual grass increase
consisted almost entirely of field (Japanese)
brome, a non-native that is considered a weed
with negative habitat and livestock value. Forbs,
most especially those of the Cichorieae tribe of
the Asteraceae family, are important for Greater
Sage-Grouse brood rearing; however, we found
no predictable change of this component with
fire. Plant species richness was lower in burned
plots. Resource managers concerned about
Greater Sage-Grouse and other sage-dependent
species should carefully consider the long-term
ramifications of prescribed burns and the effect
of wildfires on Wyoming big sagebrush habitat in
eastern Montana. Burns may essentially eliminate
sagebrush habitat, increase weedy annual grass
cover, reduce species richness, and could require a
century or more for recovery to pre-burn sagebrush
cover conditions.
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16
Appendix A. Species list of vascular plants that occurred
IN MACROPLOTS
Species list of vascular plants that occurred in macroplots; arranged alphabetically within lifeform;
constancy and average cover (%, only for plots in which sp. occurred); not stratified by burn vs. control
Latin Binomial
Common Name*
Constancy
Average cover
(%)
SHRUBS
Artemisia cana
Silver sagebrush
0.17
4.7
Artemisia tridentata ssp. wyomingensis
Wyoming big sagebrush
0.65
16.4
Chrysothamnus viscidiflorus
Green rabbitbrush
0.04
0.23
Ericameria nauseosa
Rubber rabbitbrush
0.04
0.34
Juniperus scopulorum
Rocky Mountain juniper
0.02
0.13
Primus virginiana
Chokecherry
0.02
0.005
Rhus trilobata
Skunkbush sumac
0.02
0.2
Rosa acicularis
Prickly rose
0.02
0.4
Rosa arkansana
Prairie rose
0.02
0.1
Symphoricarpos occidentalis
Western snowberry
0.04
1.4
Tetradymia canescens
Spineless horsebrush
0.10
0.17
SUBSHRUBS
Artemisia dracunculus
Terragon
0.04
0.1
Artemisia frigida
Prairie sagewort
0.75
1.4
Atriplex gardneri
Gardner's saltbush
0.04
0.3
Coryphantha vivipara
Pincushion cactus
0.04
0.02
Gutierrezia sarothrae
Broom snakeweed
0.21
0.26
Krascheninnikovia lanata
Winterfat
0.08
0.27
Opuntia fragilis
Brittle pricklypear
0.23
0.12
Opuntia polyacantha
Plains pricklypear
0.54
0.98
Yucca glauca
Soapweed yucca
0.02
0.3
GRAMINOIDS
Achnatherum hymenoides
Indian ricegrass
0.02
0.05
Agropyron cristatum
Crested wheatgrass
0.08
15.2
Aristida purpurascens
Arrowfeather threeawn
0.02
0.15
Bouteloua gracilis
Blue grama
0.81
7.2
Bromus arvensis (japonicus)
Field brome
0.90
15.2
Bromus inermis
Smooth brome
0.06
1.16
Bromus tectorum
Cheatgrass
0.15
0.9
Calamagrostis montanensis
Plains reedgrass
0.02
0.05
Calamovilfa longifolia
Prairie sandreed
0.04
1.2
Carex duriuscula (stenophylla)
Needleleaf sedge
0.06
2.1
Carex filifolia
Threadleaf sedge
0.23
1.36
Carex inops ssp. heliophila
Sun sedge
0.35
2.9
Danthonia unispicata
Onespike danthonia
0.04
0.3
Elymus elymoides
Squirreltail
0.02
0.05
Elymus (Agropyron) lanceolatus (dasystachyum)
Thickspike wheatgrass
0.08
1.9
Festuca idahoensis
Idaho fescue
0.08
44.4
Appendix A - 1
Hesperostipa {Stipa) comata
Needle-and-thread
0.60
5.4
Juncus spp.
Rush spp.
0.02
0.1
Koeleria macrantha
Prairie junegrass
0.81
3.1
Nassella {Stipa) virdula
Green needlegrass
0.63
4.8
Pacopyrum {Agropyron) smithii
Western wheatgrass
0.96
30.2
Poa pratensis
Kentucky bluegrass
0.19
4.65
Poa secunda
Sandberg's bluegrass
0.98
1.4
Pseudoroegneria {Agropyron) spicata
Bluebunch wheatgrass
0.35
4.1
Vulpia {Festuca) octoflora
Sixweeks fescue
0.44
0.8
FORBS
Achillea millefolium
Common yarrow
0.54
0.46
Agoseris glauca
Pale agoseris
0.08
0.16
Allium textile
Textile onion
0.58
0.09
Alyssum alyssoides
Pale madwort
0.75
0.02
Androsace septentrionalis
Pygmyflower rockjasmine
0.48
0.15
Antennaria neglecta
Field pussytoes
0.35
0.24
Arabis holboellii
Holboell's rockcress
0.04
0.05
Arabis nuttallii
NuttalPs rockcress
0.02
0.05
Arnica sororia
Twin arnica
0.10
1.72
Artemisia ludoviciana
White sagebrush
0.06
0.6
Asclepias spp.
Milkweed
0.02
0.05
Astragalus adsurgens
Prairie milkvetch
0.02
0.1
Astragalus agrestis
Purple milkvetch
0.27
0.21
Astragalus drummondii
Drummond's milkvetch
0.06
0.7
Astragalus plattensis
Piatt River milkvetch
0.02
0.7
Astragalus spp.
Milkvetch spp.
0.02
0.1
Bessia wyomingensis
Wyoming besseya
0.06
0.36
Borage species
Borage spp.
0.06
0.27
Brassicaeae spp.
Mustards
0.13
0.02
Calochortus nuttalliana
Sego lily
0.15
0.03
Camelina microphylla
Littlepod false flax
0.60
0.25
Cerastium arvense
Field chickweed
0.13
0.71
Chamaesyce {Euphorbia) serpylifolia
Thymeleaf sandmat
0.15
0.05
Chenopodium album
Lambsquarters
0.02
0.01
Cirsium undulatum
Wavyleaf thistle
0.02
0.05
Collinsia parviflora
Maiden blue-eyed Mary
0.06
0.04
Collomia linearis
Narrowleaf blue-eyed Mary
0.23
0.17
Comandra umbellata
Pale bastard toadflax
0.25
0.18
Conyza canadensis
Canadian horseweed
0.06
0.07
Crepis accuminata
Tapertip hawksbeard
0.02
0.25
Crepis intermedia
Limestone hawksbeard
0.04
0.07
Crepis occidentalis
Largeflower hawksbeard
0.08
0.34
Crepis spp.
Hawksbeard spp.
0.15
0.11
Appendix A - 2
Cryptantha celosioides
Buttecandle
0.13
0.07
Dalea purpurea
Purple prairie clover
0.06
0.18
Descurainia sophia
Herb sophia
0.31
0.16
Draba nemoralis
Eggleaf lacefern
0.04
0.03
Draba oligospernia
Fewseed draba
0.06
0.12
Echinacea angustifolia
Blacksamson echinacea
0.06
2.68
Epilobium paniculatum.
Tall annual willowherb
0.02
0.005
Epilobium spp.
Willowherb spp.
0.02
0.01
Erigeron caespitosus
Tufted fleabane
0.04
0.3
Erigeron pumilus
Navajo fleabane
0.17
0.07
Erigeron spp.
Fleabane spp.
0.02
0.07
Erigeron strigosus
Prairie fleabane
0.04
0.6
Eriogonum spp.
Buckwheat
0.02
0.25
Erysimum repandrum
Spreading wallflower
0.13
0.05
Euphorbia esula
Leafy spurge
0.02
0.09
Fritillaria pudica
Yellow fritillary
0.02
0.01
Galium aparine
Stickywily
0.02
1
Gaura coccinea
Scarlet beeblossom
0.13
0.06
Geum triflorum
Old man's whiskers
0.04
0.22
Hedeoma hispidula
Rough false pennyroyal
0.44
0.06
Helianthus annuus
Common sunflower
0.06
0.06
Heterotheca (Chrysopsis) villosa
Hairy false goldenaster
0.08
0.1
Heuchera parviflora
Littleflower alumroot
0.02
0.2
Hymonoxysis richardsonii
Pingue rubberweed
0.06
0.1
Ipomoxis aggregata
Scarlet gilia
0.06
0.02
Lactuca seriola
Prickly lettuce
0.21
0.31
Lactuca spp.
Lettuce spp.
0.10
0.09
Lappula occidentalis (redowskii)
Flatspine stickseed
0.15
0.06
Lewisia rediviva
Bitter root
0.04
0.26
Liatris punctata
Dotted blazing star
0.23
0.14
Linum lewisii
Lewis flax
0.08
0.14
Linum rigidum
Stiffstem flax
0.08
0.05
Lithospermum incisum
Narrowleaf stoneseed
0.04
0.07
Lithospermum ruderale
Western stoneseed
0.02
0.05
Logfia (Filago) arvensis
Field cottonrose
0.75
1.27
Lomatium cous
Cous biscuitroot
0.35
0.38
Lomatium orientate
Northern Idaho biscuitroot
0.04
0.07
Lupinus argenteus
Silvery lupine
0.02
0.5
Macaranthera canescens
Hoary tansyaster
0.04
0.1
Medicago sativa
Alfalfa
0.33
0.07
Melilotus officinalis
Yellow sweetclover
0.10
0.6
Mertensia oblongifolia
Oblongleaf bluebells
0.13
0.08
Microseris nutans
Nodding microceris
0.06
0.17
Appendix A - 3
Microsteris gracilis
Slender phlox
0.21
0.19
Musineon divaricatum
Leafy wildparsley
0.13
0.17
Nothocalais troximoides
Weevil prairie-dandelion
0.04
0.08
Oenothera caespitosa
Tufted evening -primrose
0.02
0.05
Oligoneuron rigidum
Stiff goldenrod
0.04
0.07
Orthocarpus luteus
Yellow owl's-clover
0.13
0.17
Oxytropis lagopus
Haresfoot locoweed
0.13
0.06
Oxytropis spp.
Loco weed spp.
0.08
0.15
Paronychia pulvinata
Rocky Mountain nailwort
0.04
0.12
Pediomelum argophyllum
Silverleaf Indian breadroot
0.42
0.27
Pediomelum hypogaeum
Subterranean Indian breadroot
0.02
0.05
Penstemon nitidus
Waxleaf penstemon
0.02
0.2
Penstemon spp.
Beardtongue spp.
0.17
0.13
Phacelia linearis
Threadleaf phacelia
0.06
0.1
Phlox hoodii
Spiny phlox
0.56
0.48
Picradeniopsis oppositifolia
Oppositeleaf bahia
0.10
0.71
Plantago major
Common plantain
0.02
0.05
Plantago patagonica
Woolly plantain
0.77
0.18
Pleiacanthus (Stephanomeria) spinosus
Thorn skeletonweed
0.02
0.15
Potentilla spp.
Cinquefoil
0.02
0.05
Psoralidium tenuiflorum
Slimflower scurfpea
0.15
0.74
Ratibida columnifera
Upright prairie coneflower
0.08
0.09
Selaginella densa
Lesser spikemoss
0.19
16.4
Silene antirrhina
Sleepy silene
0.04
0.03
Silene spp.
Catchfly spp.
0.02
0.005
Solidago spp.
Goldenrod spp.
0.13
0.23
Sphaeralcea coccinea
Scarlet globemallow
0.79
0.71
Stellaria spp.
Starwort spp.
0.02
0.21
Stenotus (Haplopappus) acaulis
Stemless mock goldenweed
0.04
0.2
Stephanomeria runcinata
Desert wirelettuce
0.06
0.13
Symphyotrichum falcatum var. falcatum
White prairie aster
0.06
0.11
Taraxacum officinale
Common dandelion
0.73
0.58
Tetraneuris (Hymonoxysis) acaulis
Stemless four-nerve daisy
0.04
0.82
Thermopsis rhombifolia
Prairie thermopsis
0.06
0.27
Tradescantia spp.
Spiderwort
0.02
0.01
Tragopogon dubius
Yellow salsify
0.73
0.2
Veronica arvensis
Corn speedwell
0.06
8.18
Vicia americana
American vetch
0.60
0.63
Viola nuttalliana
NuttalPs violet
0.10
0.22
Zigadenus paniculatus
Foothill deathcamas
0.04
0.05
Zigadenus venosus
Meadow deathcamas
0.23
0.25
* Common & Scientific names according to Natural Resources Conservation Service (USDA) "PLANTS" Data-
base
Appendix A - 4
Appendix B. Representative Photographs
^^^j^A54¥ a m |t *
tMft¥dutfMM**
This plot pair represents the control (top) and burn (bottom) macroplots on a productive, relatively high-elevation
site (Diamond Butte vicinity) where the control site is dominated by Wyoming big sagebrush / Idaho fescue - west-
ern wheatgrass community type. Wyoming big sagebrush canopy cover on control macroplot is 15%; there is no
Wyoming big sagebrush recovery 14 years following prescribed fire. Fescue cover (bottom; note old, tawny stems)
decreased in cover whereas western wheatgrass cover more than doubled following fire.
Appendix B - 1
This relatively dry site is characterized by a Wyoming big sagebrush / western wheatgrass - blue grama community
type on the control site (bottom). The cover of Wyoming big sagebrush is 22% in the control plot and zero in the
burned (wildfire 8 years previously); the dominant grass on both plots is field brome (Japanese brome). The cover of
western wheatgrass showed no change with burning, but blue grama cover has increased 20-fold.
Appendix B - 2
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