Sierra Nevada Grasslands: Interactions Between Livestock Grazing and Ecosystem Structure and Function

Livestock grazing plays an integral role in the grass-dominated ecosystems of the Sierra Nevada. Grazing has been asserted to influence such key ecological characteristics as water quality, net primary productivity, nutrient cycling, plant and animal diversity, wildlife habitat availability, and oak regeneration (Belsky and others 1999, Kauffmann and Krueger 1984). Although there are many reports of these effects, an important task is determining which assertion constitutes reliable knowledge. In other words, how well do we know the cause of change? In fact, there is precious little conclusive experimental evidence (Allen-v Diaz and others 1999). We do know that managers have varying control over essential elements of grazing, such as kind of grazing animal, number of grazing animals, and the season of grazing animal use. Many reports on grazing affects either fail to establish adequate experimental controls or are inadequately documented as to the details of grazing (Allen-Diaz and others 1999, Tate and others1999). The result is uncertainty about the true effects of grazing. We do know that managers can use grazing animals to achieve conservation objectives as well as limit potential adverse impacts (Allen-Diaz and Jackson [in press]).