Effects Of Nitrogen Addition On The Characteristics Of Desert Steep Communities Under Different Grazing Backgrounds In Inner Mongolia

Desert steppe is a special type of grassland in Central Asia.However,the biomass of the community in the desert steppe is under sufficient and the ecosystem is sensitive and fragile,so it is difficult to recover the destroyed ecosystem.Due to the effects of natural and artificial factors,including overgrazing and reclamation,the desert steppe is in a degraded state.Nitrogen is one of the limiting nutrient elements in plant growth,and it`s also the most deficient nutrient element.Therefore,it`s a necessary method to adding the nitrogen to the degraded steppe.So,to investigate the influence of the effective nitrogen addition to the restoration of the above-ground biomass in desert steppe under different grazing backgrounds,we conducted a nitrogen addition experiment by setting four levels of N addition treatment including 0,7,14 and 21 N·g·m^-22 added into the desert steppe community.The above-ground biomass?including total above-biomass of community and the above-ground biomass of different living function groups?,the soil/plant nutrients?TN,TP,SOC?and the soil/plant stoichiometry?C/N,N/P,C/P?under each N addition treatment and grazing background were analyzed.The following conclusions are obtained:1.Under different grazing conditions,nitrogen addition increased the above-ground biomass and soil C,N and P contents of the plant community.The recovery of the communities at 7 N·g·m^-22 of nitrogen addition under light grazing was the most effective,and 14 N·g·m^-22 is the most appropriate nitrogen addition amount for the community recovery under medium and heavy grazing conditions.2.Based on the comprehensive analysis,the contents of TC,TN and TP of plant communities under different grazing backgrounds reached the maximum value under the level of adding 14 N·g·m^-2.3.Nitrogen and phosphorus are both the limiting factors in the restoration process of plant communities under light grazing conditions.In addition to considering the addition of nitrogen,phosphorus is also considered to be added;The restoration of plant communities under medium grazing condition is mainly limited by nitrogen.The nitrogen addition level of 14 N·g·m^-22 was the most suitable for the restoration of plant communities.The restoration of plant communities under heavy grazing conditions was limited by nitrogen.After adding nitrogen,phosphorus is another necessary factor to be considered to adding to the destroyed ecosystem.