Responses of Bluebunch Wheatgrass, Idaho fescue, and nematodes to ungulate grazing in Yellowstone National Park

We sampled above and belowground biomass of Idaho fescue (Festuca idahoensis) and bluebunch wheatgrass (Agropyron spicatum) plants and nematode densities under these species inside and outside a 2-year old exclosure on the northern range of Yellowstone National Park in May through September, 1990. Native ungulates grazed the site primarily in winter and early spring. Grazing during this period removed essentially all the standing dead plant material. In early May, green biomass of plants of both species outside the exclosure was significantly lower than plants in the exclosure but off-take by ungulates accounted for only 18-51% of this initial difference. Indirect effects of grazing, such as the efftects of removing standing dead material on microclimatic conditions, likely influenced early growth (...)