Effect Of Grazing Exclusion On Soil Nitrogen And Texture Composition Of Seriphidium Transiliense Desert Grassland

To explore the effect of grazing exclusion on the soil characteristics of desert grasslands,the Seriphidium transiliense deserts in Gongliu County,Manas County,Hutubi County,and Qitai County on the northern slope of the Tianshan Mountains were taken as the objects.Determination of soil total nitrogen,alkali-hydrolyzed nitrogen,nitrate nitrogen,ammonium nitrogen,and their texture composition,to clarify the similarities and differences of their responses to grazing exclusion and use statistical methods such as Pearson correlation analysis,RDA redundancy analysis,and SEM structural equation.,to explore the regulatory effects of environmental factors such as climate factors,vegetation characteristics,and soil physical and chemical properties on soil nitrogen content and its texture composition,focusing on the analysis of the relationship between soil texture and soil nitrogen accumulation,to understand the soil nitrogen content of such degraded desert grasslands.The main research results are as follows:(1)Overall,the height,coverage,above-ground biomass,semi-shrub biomass,annual biomass,and litter biomass of the desert grassland community of Seriphidium transiliense increased significantly by131.04%,50.29%,80.80%,96.11%,176.19%,76.29%(P<0.05),and the community density,Patrick index,Shannon-Wiener index,Simpson index,and Pielou index decreased significantly by 14.38-22.67%(P<0.05).After grazing exclusion,soil water content,p H,electrical conductivity,organic carbon,total phosphorus,and available phosphorus in the desert grassland of Seriphidium transiliense did not increase or decrease significantly(P>0.05),while soil bulk density decreased significantly(P<0.05).(2)After grazing exclusion,the content of inorganic nitrogen in the 0-50 cm soil layer of Seriphidium transiliense desert grassland decreased significantly(P<0.05).and the nitrate nitrogen content decreased the most 11.11%(P<0.05),while the soil nitrogen density,total nitrogen,alkali-hydrolyzable nitrogen,and ammonium nitrogen contents did not change significantly(P>0.05).Regardless of grazing exclusion or not,there was a significant correlation between soil nitrogen and climate,vegetation,and soil physical and chemical factors(P<0.05),and after grazing exclusion,soil total nitrogen was negatively correlated with litter biomass and vegetation diversity.Positive correlation,nitrate nitrogen,and above-ground biomass changed from negative correlation to positive correlation,and community height,cover,bulk density,p H,electrical conductivity from positive correlation to negative correlation,and ammonium nitrogen and litter from negative correlation.Turned to positive correlation,and community density,soil bulk density from positive correlation to negative correlation.The partial redundancy analysis showed that the main factors affecting the effect of vegetation on soil nitrogen after grazing exclusion were below-ground biomass and Patrick index,with explanation rates of 45.3% and 16.1%,while soil physicochemical properties were mainly organic carbon,available phosphorus,and For total phosphorus,the explanation rates were 31.3%,30.5%,and 27.2%.(3)Grazing exclusion decreased the soil sand content in the 0-50 cm soil layer of the Seriphidium transiliense desert grassland,and significantly increased the soil clay content(P<0.01).Overall,there was a significant correlation between soil texture composition and climate,vegetation,and soil physicochemical factors(P<0.05),and after grazing exclusion,soil silt,clay and vegetation diversity,soil p H,and water content were negatively correlated.becomes a positive correlation.The partial redundancy analysis showed that the main factors affecting the soil texture composition after grazing exclusion were the Simpson index,community coverage,and Patrick index,and the explanation rates were 32.4%,33.2%,and 25.4%,while soil physicochemical properties were the main factors.are soil bulk density and p H,and the interpretation rates are 41.7% and 20.7%.(4)There was a significant correlation between soil nitrogen and texture composition in the desert grassland of Seriphidium transiliense(P<0.05),and soil nitrogen showed a decreasing trend with the increase of soil sand content,and with the increase of soil clay content and increase.The SEM results showed that the direct effect of vegetation diversity on soil nitrogen was the highest(-0.51),followed by soil texture(0.41),indicating that vegetation diversity had a negative regulatory effect on soil nitrogen,and soil texture had a negative effect on soil nitrogen.It has a positive regulation effect,in which soil clay indirectly affects soil nitrogen by affecting the vegetation community(0.87),while soil available phosphorus,total phosphorus,and organic carbon indirectly affect soil nitrogen mainly by affecting vegetation diversity(0.58).make an impact.