Small Mammal and Plant Community Responses to Mechanical Disturbance and Rest in Wyoming Big Sagebrush Grassland

Our aim in this study was to evaluate short-term (2 years) responses of several attributes of small mammal populations (species richness, abundance, diversity, and similarity) and plant community dynamics (species richness, canopy cover, above-ground biomass production, and diversity) to the mechanical disturbance associated with interseeding. Small mammal live trapping and vegetation sampling were conducted in 2004 and 2005 on replicated 1ha study plots in a native Wyoming big sagebrush (Artemisia tridentata Nutt ssp. wyomingensis Beetle Young)-grassland that were: 1) mechanically disturbed in April 2003 and rested from grazing during the study (mechanical); 2) rested from grazing (rested); and 3) moderately grazed by cattle (grazed). Deer mice (Peromyscus maniculatus), northern grasshopper mouse (Onychomys leucogaster), and sagebrush vole (Lemmiscus curtatus) were the primary small mammal species captured during 7776 trap nights in 2004 and 2005. Small mammal diversity was greater for the mechanical (H'=1.22) than the rested (H'=0.85) treatment with the grazed treatment intermediate. Plant community variables of species richness, diversity, similarity, and above-ground biomass production did not differ among treatments. Canopy cover of the dominant species, Wyoming big sagebrush, was reduced 20-34% by the mechanical disturbance (6.9%+/- 1.0) compared to rested (8.6%+/- 0.6) and grazed (10.4%+/- 1.0) plots. The mechanical disturbance affected approximately 10.5% of the ground surface area but this had little impact on short-term small mammal or plant community dynamics in this rangeland ecosystem.