Grazing impact on plant seed production in Southern Mongolia

Nomadic livestock husbandry practices have a long history in Mongolia and still represent the main form of land use. Because of increasing livestock numbers, the danger of overgrazing and steppe degradation is on the rise. Nevertheless, studies on the infl uence of herbivores are rather rare in southern Mongolia and existing studies focus mainly on biomass production rather than on the consequences to reproduction of key steppe plants. We tested the effect of grazing by livestock and small mammals on the production and related seed abundance of three of the most dominant steppe plant species of the Mongolian desert steppes:Agropyron cristatum, Stipa krylovii and Artemisia frigida. The fi eldwork took place in summer 2006 in the Gobi Gurvan Saykhan National Park, during which we estimated the extent of granivory and compared the abundance of infl orescences on grazed/ungrazed sites and the harvesting preferences of small mammals. Herbivory has a tremendous impact on fl ower and, subsequently, seed production of the three studied species. Flowers and fruits are browsed at levels of up to 100%. However, grazing pressure is plant-specifi c; both livestock and small mammals have feeding preferences, and pikas (Ochotona pallasi) prefer taxa such as Stipa spp. Granivory, in contrast does not seem to play any role for the three studied species growing in the southern Mongolian steppes.