Small Mammal Populations in an Unburned and Early Fire Successional Sagebrush Community

Abstract

Species composition and total numbers of small mammals changed little in the unburned sagebrush while individual species capture rates varied considerably. Following spring burning, the number of small mammal species and abundance were slightly. lower than control levels and were near unburned levels after 3 years. Species composition was greatly reduced on the fall bum in the first postburn year. Two years after burning four species were captured, although only two were caught in live-traps. Total small mammal density increased dramatically in the first two postburn years. The large increase in abundance on both bums was due primarily to Peromyscus maniculatus and Spermophilus armatus. Food use patterns on the fall burn were similar to those observed on the spring burn where small mammals utilized their preferred food types in relation to its abundance and availability. National Park. In unburned areas mountain big sagebrush (Artemisia tridentata vaseyana) is the most abundant shrub, forming dense, homogeneous stands. The most common grasses are wheatgrasses (Agropyron spp.), Idaho fescue (Festuca idahoensis), bluegrasses (Poa spp.) and needlegrasses (Stipa spp.). Characteristic forbs include yarrow (Archillea millefolium), wild buckwheat (Eriogonum umbellatum), geranium (Geranium spp.), lupine (Lupinus spp.), and northwest cinquefoil (Potentilla gracilis). Grasses and forbs form a continuous understory with few open areas. The sagebrush is bordered by stands of Douglas-fir (Pseudotsuga menziesii) and aspen (Populus tremuloides).