Big sagebrush (Artemisia tridentata) ecology and management with emphasis on prescribed burning

Graduation date: 1983Four studies were conducted. First, mountain big sagebrush communities were burned at Lava Beds National Monument, California, and The Crooked River National Grassland, Oregon. In two years at Lava Beds, basal cover of Idaho fescue in one community and Thur- ber's needlegrass in one of three communities did not recover. Basal cover of bluebunch wheatgrass and Sandberg's bluegrass re- covered or increased above prefire levels at the expense of Idaho fescue and Thurber's needlegrass. Bunchgrasses recovery was based on height and production which increased to equal or exceed prefire levels. At Crooked River, height and production of bluebunch wheat- grass were much higher than prefire levels, but basal cover remain- ed extremely low after two years. Prescribed burning recommenda- tions were presented. Secondly, after hot and cool in situ propane barrel burns, mountain big sagebrush seed emergence in the greenhouse was stimu- lated. Basin big sagebrush seed emergence was reduced by both fire intensities. Emergence was inverse to fire intensity for both sub- species. Wyoming big sagebrush was not affected by fire. Both in- tensities reduced emergence of most herbaceous species from mountain big sagebrush dominated soils. Hot fires were required to reduce emergence of the few herbaceous species affected by fire on basin and especially Wyoming big sagebrush dominated soils. A trend of in- creasing fire resistance with increasing site severity was evident. Thirdly, individual and area fuel loading equations were de- veloped for each component of fuel of the three subspecies of big sagebrush. R² values for individual shrub equations ranged from .36 to .96. Line intercept cover, the number, and the height of intercepted shrubs were used to estimate area fuel loadings with R² values ranging from .42 to .84. This method of estimating area fuel loading provides relatively high precision at reduced cost. Fourthly, basal cover and leaf length or plant height were used to estimate bunchgrass production. R² values for burned plant equations were higher (.66-.87) than R² values for unburned- ungrazed plant equations (.35-.85). Basal cover accounted for at least 70 percent of the variation in Thurber's needlegrass, burned Idaho fescue, and burned bluebunch wheatgrass production. Comparisons based on indirect estimation yielded results comparable to clipping