Livestock grazing: Animal and plant biodiversity of shortgrass steppe and the relationship to ecosystem function
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Authors: D. G. Milchunas, W. K. Lauenroth, and I. C. Burke
Date: 1998
Journal: Oikos
Volume: 83
Number: 1
Pages: 65-74
Summary of Methods: 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.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: grazing treatments, diversity, abundance, trophic structure, ecosystem processes
Annotation: Grazing treatments of light, moderate, and heavy stocking rates (each approx. 130 ha), and ungrazed controls, were established in 1939 on areas that were not previously overgrazed. Grazing occurred during the growing season (May-November) with stocking rates for a particular year depending on the number of animals necessary to remove approximately 20, 40, and 60% of forage production.
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