A Study On Spatial Variability Of Soil Carbon And Nitrogen And Effects Of Environmental Factors On Plant Community Characteristics In Xilin River Basin

The Xilin River Basin is the most representative area of the typical steppe in Inner Mongolia.With the increase of the intensity of human activities and the deterioration of the natural environment,the grassland ecosystem has been seriously damaged,and the study of vegetation-environment relations has become one of the major issues of sustainable development.In this paper,the grassland of Xilin River Basin is the research object,based on the sample survey and experimental data,the semi-variance function theory was used to describe the spatial variation of soil organic carbon and total nitrogen.TWINSPAN,RDA and GAM were used to study the distribution characteristics of plant community and its characteristics.The direct and indirect effects of environmental factors on aboveground biomass,underground biomass and underground/aboveground biomass ratio were studied by regression analysis,path analysis and decision coefficient analysis,and to analyze the main environmental factors affecting the distribution,diversity and biomass of vegetation communities in Xilin River Basin,and to provide basic data for soil fertility evaluation and rational utilization of soil resources,and to provide the basic data for soil organic carbon and total nitrogen spatial variation.Plant species diversity protection,grassland ecosystem restoration and the development of scientific and rational grazing policy to provide theoretical basis The main results are as follows:(1)The SOC and TN contents in the layers of Xilin River Basin are lower than those in the middle and below.The geochemical analysis showed that the best fitting model of soil SOC and TN content was slightly different,and the maximum spatial correlation distance was different.However,with the increase of soil depth,the spatial distribution of SOC and TN increased.Random factors lead to weakened degree of variation.The results show that soil dry bulk density and soil electrical conductivity are important factors affecting the SOC and TN contents in 0-10cm layer,and the important factors affecting SOC and TN in 20-30cm layer SOC,TN and 40-50cm layers are Soil dry bulk density and soil saturated water content.(2)TWINSPAN classification indicated that 55 herbaceous plants were classified into 5 community types.The results showed that elevation,SOC and TN content were the main environmental factors affecting the species diversity,and the different environmental factors affected the importance of different dominant species,and the response degree of different dominant species to the same environmental factors was different.The RDA sequencing shows that the combination of selected environmental factors explains 61.6%of the species compositional characteristics of the variation,from the total effect of 0-10cm and 20-30cm layer conductivity,20-30cm and 40-50cm layer pH,0-10cm layer SOC and TN are the key factors affecting the distribution of species.From the net effect,only 0-10cm layer conductivity,0-10cm layer TN has a significant impact on species distribution.(3)The correlation analysis showed that the aboveground biomass had a significant correlation with altitude,annual precipitation and growing season average temperature(p<0.05).Underground biomass and altitude,growth season precipitation,average temperature in growing season,annual average temperature,0?(p<0.05).The ratio of root to shoot was higher than that of soil organic carbon and total nitrogen,soil saturated soil moisture at 0-10 cm layer,and soil water content(p<0.05).Path analysis showed that the main control effect on the aboveground biomass was the average temperature in the growing season.The main controlling effect on the underground biomass was the precipitation season,the annual average temperature and the soil organic carbon content.