Study On The Effects Of Precipitation Variability On The Stability Of Semi-arid Desert Steppe Ecosystem In Western Loess Plateau

With the global warming,the precipitation pattern has changed significantly.Precipitation is an important source of water in arid and semi-arid ecosystems and a key driver of biological processes at different spatial and temporal scales.Therefore,how precipitation changes affect plant community characteristics,soil nutrient status and ecosystem stability is an important content of grassland ecology research.Desert steppe is the transition vegetation type from steppe to desert,which plays an important role in maintaining the stability of regional ecosystem.Precipitation is the main replenishment source of water resources in the desert and grassland region of the western Loess Plateau,but heavy rain often leads to severe soil and water loss.Therefore,the study of the impact of precipitation change on the stability of desert steppe ecosystem in the western Loess Plateau and its mechanism can provide scientific basis for the scientific assessment of the response of semi-arid desert steppe ecosystem to precipitation change,and also provide theoretical support for the sustainable utilization and management of desert steppe.This study in the Loess Plateau in the western desert grassland as the research object,to carry out field precipitation controlled experiments,through field investigation to obtain data of vegetation and soil physical and chemical properties of laboratory analysis to obtain the data,the variance analysis method under different precipitation process clear the plant community characteristics,characteristics of soil physical and chemical properties and the characteristics of ecological system stability.Correlation analysis was used to analyze the plant and soil factors affecting ecosystem stability.Structural equation model(SEM)was used to reveal the main mechanisms affecting the stability of semi-arid desert steppe ecosystem under precipitation alteration.The main research results are as follows:(1)The plant species composition is simple,and the influence of precipitation changes on forbs species is more obvious.In normal years and dry years,the effect of precipitation treatments on plant community diversity was more obvious.In wet years,the effect of precipitation treatments on plant community diversity was not obvious.In normal precipitation years,the effect of precipitation treatments on community biomass was not obvious.In wet years,the effect of extreme drought(40%precipitation reduction)on community biomass was more obvious.In dry years,the effect of precipitation increasing treatments on community biomass was more obvious.Precipitation has a significant effect on the biomass of forbs species,which regulates the biomass change of the community.With the passage of precipitation treatments year,the influence of precipitation treatments on community biomass increased.Precipitation change significantly affected species asynchrony(P<0.05).The precipitation change had no significant effect on the stability of ecosystem,but had significant effect on the stability of forbs(P<0.05).(2)With the passage of precipitation treatment time,the influence of precipitation treatments on surface soil water content increases.In normal and dry years,soil nutrients and soil C:N:P ecological stoichiometry showed a decreasing trend with the increase of precipitation,and C:N was significantly decreased(P<0.05).In wet years,it showed an upward trend with the increase of precipitation.(3)Species richness had little effect on ecosystem stability,but precipitation changes affected species asynchrony mainly by controlling soil nitrate nitrogen.Species asynchrony affected the changes of ecosystem stability,and species asynchrony was the main mechanism regulating the changes of ecosystem stability.This study is helpful to explore the effects of precipitation changes on the characteristics of plant communities and soil factors in the desert steppe,the characteristics of ecosystem stability and the main mechanisms affecting the stability of the ecosystem,which has important guiding significance for the protection of species diversity in the desert steppe and the maintenance of ecosystem stability in the future.