Seedling establishment following deferment in simulated rest-rotation and deferred-rotation grazing systems on a Utah summer range

Controlled trampling by a sheep and a horse was used to test the hypothesis that deferment of grazing until seedset will enhance seedling establishment. The study was conducted on a grassland summer range in southwestern Utah at 2600-m elevation and with mean annual precipitation of 750 mm. The trampling regimes of 4 grazing treatments were imposed in 1994-95: rest-rotation grazing; deferred-rotation grazing; season-long grazing; and no grazing. Known seed numbers of 4 native forb species were scattered on the plots in August 1994. Deferment in 1994 did not enhance seedling establishment compared to season-long (continuous) grazing. Protection from grazing in 1995 (rest-rotation) reduced seedling mortality that year. There were no differences between the small and large herbivore. Seedling success was strongly associated with surface litter, proximity to grass tussocks, and hoofprint depressions. Seedlings failed to establish on bare soil created by gopher disturbance.