Survival of perennial grass seedlings under intensive grazing in semi-arid rangelands

(1) The hypothesis that intensive grazing practices such as short-duration grazing, benefit seedling survival through hoof action of the trampling animals was tested in a one-year study. Estimation of survival rates and hypothesis testing followed the numerical optimization approach to maximum likelihood analysis. (2) A total of 1598 crested wheatgrass seedlings (Agropyron desertorum (Fisch. ex Link) Schult.), of which 52.5% were protected from livestock grazing, were involved in the study. Seedling survival did not differ significantly between grazed and ungrazed populations prior to the first grazing treatment. (3) Grazing reduced seedling survival significantly in the first as well as in a second three-day grazing period. The treatment effect was most pronounced in the second grazing period. (4) Ten months after cattle were removed from the pastures the two 3-day grazing treatments continued to influence survival of seedlings. Of the 759 seedlings recorded in grazed plots only three survived 1 year after their emergence. In contrast, ninety-seven seedlings survived 1 year in the protected plots where 839 seedlings germinated. (5) Crested wheatgrass seedling survival in relation to the proximity of their well-established parent plants, was also investigated. The majority of seedlings (56%) emerged in bare soil more than 10 cm away from established grasses. Survival was more related to grazing treatment than to seedling location.