Responses of Plant Community and Soil Properties to Inter-Annual Precipitation Variability and Grazing Durations in a Desert Steppe in Inner Mongolia

Grazing can dramatically affect arid grassland communities that are very vulnerable to environmental changes due to its relatively short and sparse ground coverage, low biomass, sandy soil and inter-annual precipitation found in the desert steppe. The study investigates the effects of different grazing durations on vegetation and soil properties of a desert steppe community. The experiment was conducted in Xisu Banner in Inner Mongolia with five treatments: CG (continuous grazing), 40UG (40 d ungrazed), 50UG (50 d ungrazed), 60UG (60 d ungrazed) and UG (ungrazed). The biomass of both shrub and annual-biennial plant communities were significantly decreased by CG. Continuous grazing and 40UG significantly reduced the ANPP (aboveground net primary productivity) by the end of the three year study. 60UG treatment increased soil organic carbon (OC), total nitrogen concentration (TN) and total phosphorus concentration (TP) concentrations and 50UG increased the TN and total phosphorus concentration (TK) concentrations, whereas CG, 40UG and 50UG decreased soil OC, TP and available phosphorus concentration (AP) concentrations. The perennial plant species of the desert steppe were generally tolerant for grazing. The annual-biennial plant species had large variability in ANPP because of the inter-annual precipitation. Our results highlight that inter-annual precipitation variations could strongly modify the community responses to grazing in arid ecosystems.