Abstract: To discuss the variation of aboveground standing biomass of desert steppe under seasonal regulation of grazing intensity and the relationship between grazing intensity and seasonal regulation, we collected the observational data of the aboveground standing biomass in Stipa breviflora desert steppe of the Mongolian Plateau in September 2010-2014, and analyzed the standing aboveground biomass in the desert steppe using comparative analysis and regression modeling. The results showed that there were significant differences in both experimental treatments and years on the aboveground standing biomass in the desert steppe (P<0.01), and the grazing treatment effect was greater than the interannual biomass change caused by the variations of annual precipitation and air temperature. Regression modeling analysis showed that a general model could be used to predict the aboveground standing biomass changes of 27 experimental treatments and its fitting rate was more than 99% by 6 experimental treatments. The model also showed that the increased grazing intensity in spring could lead to decreased grassland utilization, and the grazing intensity of previous season can significantly affect the grazing of subsequent season. Different grazing seasons had additive effects, which led to an amplified influence of the previous grazing in the subsequent grazing season, and thus reduced the recoverability of grassland after heavy grazing.

Key words: irrigation amount, fertigation, water use efficiency, yield, quality, cucumber.