| Ungulate populations are managed in shrub-steppe ecosystems around the world, but relatively few long-term datasets are available to test the impacts of these grazers on ecosystem structure and function. This study examined the effects of low (100/100 km2), moderate (240/100 km2), and high (1,920/100 km2) densities of deer and elk over 35 and 55 years in shrub-steppe ecosystems located throughout central Washington State on: (1) vegetative structure and composition, by evaluating biomass, percent cover, and species richness; (2) soil properties, by measuring net nitrogen (N) mineralization and net nitrification rates, Olsen extractable phosphorous (P), carbon (C):N ratios, and soil moisture; and (3) arthropod diversity and abundance. The site with the highest ungulate density had greater vegetative cover and biomass inside of the exclosures than outside; the moderate density site had no vegetative biomass or cover differences inside and outside of the exclosures; and the site with the lowest density had greater shrub cover outside of the exclosures than inside, but no treatment differences for biomass. (Abstract shortened by UMI.)... |
