Livestock Exclosure Study: Plant Species Composition in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (2004-2007)

Grazing in grasslands creates changes in plant community structure. The magnitude of these changes depends on the productivity and the intensity of grazing. Low productivity grasslands coupled with high grazing intensity may lead to shrub encroachment in some aridland ecosystems. We examined the effects of cattle grazing in arid grassland at the Sevilleta LTER site in central New Mexico USA where cattle were removed in 1973 and an area just north of the Sevilleta LTER where grazing by cattle still occurs. At each site we measured plant species composition and cover in permanent plots in the spring and fall from 2004 to 2007. Quadrats were clipped annually to quantify aboveground standing crop to answer the following questions: 1) Does cattle grazing affect plant species composition and standing crop? 2) Does grazing alter community response to inter-annual climate variability? and 3) How does grazing impact the abundance of native grasses?