• CASE NAME
• SEASON/SEVERITY CLASSIFICATION
• STUDY LOCATION
• PREFIRE VEGETATIVE COMMUNITY
• TARGET SPECIES PHENOLOGICAL STATE
• SITE DESCRIPTION
• FIRE DESCRIPTION
• FIRE EFFECTS ON TARGET SPECIES
• FIRE MANAGEMENT IMPLICATIONS

CASE NAME:

Effects of prescribed fire on antelope bitterbrush in Wyoming

REFERENCE:

Cook, J. G.; Hershey, T. J.; Irwin, L. L. 1994 [58]

SEASON/SEVERITY CLASSIFICATION:

One fire took place in June, one in September, and one in April.

STUDY LOCATION:

Three prescribed burned sites within 30 km of Encampment, in south-central Wyoming.

PREFIRE VEGETATIVE COMMUNITY:

The sites were dominated by antelope bitterbrush (Purshia tridentata), mountain big sagebrush (Artemisia tridentata ssp. vaseyana), and Saskatoon serviceberry (Amelanchier alnifolia). Common graminoids included bluebunch wheatgrass (Pseudoroegneria spicata), spike fescue (Leucopoa kingii), needle-and-thread grass (Hesperostipa comata), and Ross sedge (Carex rossii). Areas surrounding the study sites support quaking aspen (Populus tremuloides) and lodgepole pine (Pinus contorta) communities.

TARGET SPECIES PHENOLOGICAL STATE:

No entry

SITE DESCRIPTION:

Climate is semi-arid. The authors describe the study sites as high elevation and mesic, which is not typical antelope bitterbrush habitat. The region's average precipitation is 38 cm; average temperature is 5§ C. At approximately 2,400 meters, the study sites were slightly higher in elevation than regional climate stations, so they are probably wetter and cooler than these averages. Study sites are in steep canyons with lithic soils of igneous and metamorphic bedrock. The sites have east aspects. Mule deer and Rocky Mountain bighorn sheep use the area often; elk and pronghorn use it occasionally.

FIRE DESCRIPTION:

There is no specific information available about the fires themselves, but the following table outlines some environmental conditions on the study sites at the time of the fires.

               Date     Temp.(oC)   Rel. Hum. (%)  Wind (km/h)
Douglas Cr.    6/85     26          24             16-20
Encamp. NE     9/85     17          33             13-20
Prospect Mt.   4/87     11          17             5- 7

FIRE EFFECTS ON TARGET SPECIES:

The following table describes survival (% of prefire density +/- 95% confidence intervals) of antelope bitterbrush after prescribed burning from 1986 to 1989. All antelope bitterbrush plants at the Douglas Creek study site died after burning.

               Postfire year 1    Postfire year 2    Postfire year 3
Douglas Cr.    0                  0                  0
Encamp.  NE    47 +/- 10          35 +/-  9          34 +/-  9
Prospect Mt.   66 +/- 12          56 +/- 12          56 +/- 12

FIRE MANAGEMENT IMPLICATIONS:

The Douglas Creek burn that killed all of the antelope bitterbrush on site was a summer burn with the highest temperature and the greatest wind speeds of the three prescribed burns. Relative humidity was low. The habitat type investigated in this study is higher and more mesic than typical antelope bitterbrush habitats. Therefore, conclusions drawn in this study may not be universally applicable. However, findings of this study concur with much of the literature. Summer burning is most likely to kill antelope bitterbrush outright. Spring burning, when carbohydrate stores in the roots are highest, is most appropriate to encourage survival and sprouting of antelope bitterbrush.

While postfire density of antelope bitterbrush varied from 34 to 56% of prefire levels, increases in twig production increased biomass after fire, so postfire and prefire biomass were roughly equal. Fire may be a useful tool to enhance ungulate habitat by reducing standing dead matter, opening the canopy for grass production, and stimulating antelope bitterbrush twig growth.

Related categories for SPECIES: Purshia tridentata | Antelope Bitterbrush