Degradation and decreasing productivity increasingly demand sustainable grazing management practices within Inner Mongolian steppe ecosystems. This study focuses on grazing-induced degradation processes over a wide range of stocking rates and aims to identify short-term sensitive indicators and alternative management practices. Short-term effects of 2 grazing management systems (Mixed System and Traditional System) and 7 stocking rates (SR0, SR1.5, SR3, SR4.5, SR6, SR7.5, and SR9 for 0,1.5, 3, 4.5, 6, 7.5, and 9 sheep/ha, respectively) on yielding performance and herbage quality were measured on experimental plots in which moveable exclosures were used on areas chronically grazed by sheep. The experiment was conducted in a typical steppe ecosystem in Inner Mongolia, P. R. China. Results are presented for 2005 and 2006. Sampling time was the main factor affecting yield and quality. Stocking rate also showed considerable effects on yield. Herbage mass decreased linearly from SR0 to SR9, by 85% and 82% in 2005 and 2006, respectively. Herbage accumulation was also affected by stocking rate, and was highest at SR1.5 and clearly reduced at SR9. Grazing effects on relative growth rate indicated grazing tolerance of plants in the short-term, since up to high stocking rates, relative growth rates remained stable. Precipitation also determined plant responses to increasing levels of grazing. The year of higher rainfall generated higher grazing tolerance of plants and higher herbage growth than the drought year. Despite considerable reduction of herbage mass, consistent short-term responses of herbage quality to grazing in 2005 and 2006 were reflected only in terms of crude protein and acid detergent lignin. Herbage crude protein content was highest at SR7.5 and SR9, while lignin was lowest at SR7.5 and SR9. Neither productivity nor herbage quality was affected by the management system, suggesting that both systems may be applicable on typical steppe in the short-term.

Context Many studies have examined how intensity of grazing and patterns of precipitation individually and interactively influence the spatial and temporal dynamics of grassland vegetation, such as dominance, succession, coexistence, and spatial heterogeneity. However existing models have rarely considered the diet preferences of grazers and how they interact with variation in precipitation amount and timing. Objective and methods We examined how plant community structure responds to the individual and combined effects of grazing intensity, selective grazing, and patterns of precipitation, based on a six-year grazing experiment with seven levels of field-manipulated grazing intensity in a typical steppe of Inner Mongolia. Results The palatable species, mainly forbs, were most severely damaged at intermediate levels of grazing intensity; given that these species are the major contributors to plant community diversity, a U-shaped diversity-grazing intensity relationship resulted. In contrast, spatial heterogeneity of aboveground biomass and species composition peaked at intermediate levels of grazing intensity. Cold season precipitation positively correlated with the abundance of the dominant C 3 grasses and correlated negatively with the subdominant forbs and C 4 plants. Thus, when cold season precipitation increased, plant community species diversity decreased. Grazing intensity and Electronic supplementary material The online version of this article (precipitation did not interact in their effects on species richness. Conclusions These findings contrast with the predictions from current disturbance-diversity models and indicate that diet selection of grazing animals is an important factor shaping the diversity-grazing intensity relationship in semi-arid grasslands. Future grassland biodiversity conservation and management practices should take diet preference of grazing animals into account.

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