Milchunas et al. synthesized new and previously-published data from long-term grazing treatments in North America shortgrass steppe on diversity and abundance of plants, lagomorphs, rodents, birds, macroarthropods, microathropods and nematodes. Birds appear to be particularly responsive to grazing. Differences among treatments in richness within groups other than plants and birds were relatively minor, especially when compared to large declines in abundance of some groups with increasing grazing intensity. Aboveground macroarthropod and lagomorphs were the most heavily influence by grazing. Lagomorphs had highest abundance in moderately grazed treatments relative to both heavily and lightly grazed. Aboveground macroarthropods of all trophic groups showed small increases with light grazing intensities, followed by large decreases with moderate and heavy grazing. The impact of grazing caused only small differences in the abundance of litter-plus-soil microarthropods in lightly versus heavily grazed treatments. An assessment of two groups at a species level for which quality classifications can be made (plants-exotics, weeds vs. native, perennials; birds-endemic, declining or low populations vs. secondary, abundant, and widespread) reinforce the importance of herbivory in a system with a long evolutionary history of grazing by native large ungulates. Further, large effects of grazing on some consumer groups did not translate into similarly large effects on ecosystem processes such as primary production or soil nutrient pools and cycling rates.
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