Effects of Jackrabbit Grazing, Clipping, and Drought on Crested Wheatgrass Seedlings

Abstract

The effects of black-tailed jackrabbits on crested wheatgrass (Agropyron desertorum) seedling establishment and utilization were monitored on a mesic and 2 xeric Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) sites in Nevada. Although jackrabbit densities (1.4 to 2.9/ha) and utilization were high, seedling survival was not significantly different (p≤0.05) inside or outside rabbitproof exclosures even on the xeric sites during drier-than-normal springs. Seedling density was greater on the mesic than xeric sites, but good grass stands were produced on all sites. The smaller seeded areas (less than 60 ha) and the edge of the large seeded area (400 ha) had the greatest forage utilization by rabbits. To determine the effects of defoliation and drought on seedling survival, seedlings in small tubes (3.8 cm diameter and 20 cm deep) and in large tubes (10 cm diameter and 1 m deep) were watered and clipped at 7 different intervals. Seedlings grown in the smaller volume were more sensitive to clipping and drought than those grown in the larger soil volume. Seedlings watered less than weekly showed a trend toward higher survival when clipped every 3 or 4 weeks than when clipped more or less frequently. Clipping weekly and watering less than weekly greatly reduced root growth and seedling survival. Although infrequent grazing by rabbits could slightly increase seedling survival in a dry year, the additive effects of frequent grazing and drought could result in stand failure, especially on shallow or rocky soils with a small soil volume that limits water retention and root growth.