Study On The Stability And Affecting Factors Of Soil Organic Carbon Pool Of Three Typical Community In Desert Steppe

Under the background of global warming,various environmental problems have attracted widespread attention,which has made the study of carbon cycle become one of the hotspots for international scholars.The energy balance and environmental change trends of the entire earth system are affected by the terrestrial carbon cycle.Desert grassland is one of the main land ecosystem types,and the study on soil organic carbon pool of desert grassland is of great significance to evaluate the benefit of regional vegetation restoration and promote ecological balance.Three typical communities of Caragana korshinskii,Artemisia ordosica,and Agropyron mongolicum under different degradation degree and vegetation types,was be choosed for analysis in desert grassland located in east Ningxia Hui Autonomous Region,China.In this study,three typical communities of desert steppe in eastern Ningxia were selected as the research object to study the vegetation characteristics of different typical communities,soil physicochemical properties,biological characteristics soil organic carbon,and carbon pool stability was determined in this study.Meanwhile,the stability of organic carbon pool and its relationship with influcing factors in desert grasslands was discssed through redundancy analysis(RDA),correlation analysis and regression analysis.The main findings are as follows:(1)There are 27 species of plants belonging to 11 families and 25 genera of three typical communities in the desert grassland including 8 kinds of Leguminosae and 5 kinds of Gramineae,which is the dorminant vegetation types in the desert grassland area.Lespedezabicolor,Artemiascoparia,Ixeridiumhinense,Corisprmumchinganicum,Salslacolina and Euphorbiapeinensis were found in the three typical communities and are widely distributed.The community of artemisia sphaerocephala is rich in species composition,and there are 19 species of plant symbiosis,with species diversity index,evenness index and dominance index all reaching the maximum.The species composition of Artemisia ordosica community is abundant,and 19 kinds of plants are symbiotic,with the diversity index,evenness index and dominance index of species reaching the maximum.(2)Soil moisture content and bulk density of the three typical communities outside the plexus are larger than those in the plexus,and soil solidity,saturated soil moisture content,and electrical conductivity are opposite,with significant differences among different habitats(P<0.05).The porosity in shrub and semi-shrub communities within the plexus is greater than that outside the plexus,while it is inverse in herb communities.The porosity is significant difference among different communities(P<0.05).The soil particle size distributions of the three typical community types is "single-peaked",which mainly concentrates in the particle size composition of 2-250?m.The particle size content of 2-50?m and 100-500?m is the main cause of the difference among communities,and soil particle size distribution among different communities differ significantly(P<0.05).The variation range of fractal dimension D is between 2.56 and 2.63,while the fractal dimension of artemisia sphaerocephala is the smallest and the difference among different communities is significant(P<0.05).The fractal dimension D ranges from 2.56 to 2.63,and the D value of Artemisia ordosica community is the smallest,with significant differences among different communities(P<0.05).(3)The soil nutrient distribution of three typical communities in desert grassland shows obvious"fertile island" effect,and the values of soil organic matter,total nitrogen,and total phosphorus are all larger in the plexus than those outside the plexus.The activities of urease,sucrose enzyme and catalase were higher in the typical communities,and alkaline phosphatase was different in different habitats.The microbial biomass nitrogen and microbial biomass carbon entropy in the typical desert grassland communities,and microbial biomass carbon and microbial biomass carbon and nitrogen ratio in the shrub communities are greater in the plexus than those outside the plexus.The biological properties of Agropyron mongolicum with other communities are significant difference(P<0.05).(4)The soil organic carbon(SOC)content is significantly different among the three typical communities in desert grassland,whose values are higher in the plexus than those outside the plexus in the same community.While the SOC content among different communities is as follows:Caragana korshinskii>Agropyron mongolicum>Artemisia ordosica,with significant differences among different communities and habitats(P<0.05).The soil oxidizable organic carbon in the three typical communities is relatively high,while the trend of soluble organic carbon and oxidizable organic carbon is completely opposite,with significant difference among different habitats(P<0.05).The content of silt-clay organic carbon and active organic carbon are the highest in the same community,followed by the content of coarse sand organic carbon.(5)In the shrub community,the activity of carbon pool is higher in the plexus than that outside the plexus with a large difference,while it is opposite for the herb community.The management index of soil carbon pool in the shrub community is relatively high,and the change trend is different among different babitats.The results shows that different typical communities in desert grassland creates different microenvironment for soil organic carbon sequestration,which significantly improves soil organic matter status and soil carbon pool quality.(6)The vegetation factors,soil characteristics and organic carbon compostion content in desert grassland all have some effects on the stability of soil carbon pool.The total coverage,particle size fraction of less than 500 ?m,soil nutrient,sucrose enzyme,urease and microbial biomass all have positive effects on soil carbon pool activity and carbon pool management index.Soil bulk density,composition content of 50-250 ?m particle size,alkali solution nitrogen,total phosphorus and available phosphorus and silt-clay organic carbon,coarse sand organic carbon,and soluble organic carbon are the direct factors affecting the stability of soil carbon pool.Microbial biomass carbon,microbial biomass carbon,carbon-nitrogen ratio of microbial biomass and catalase activity have indirect effects on the stability of soil carbon pool.