Spatial Characteristics And Influencing Factors Of Soil Carbon And Nitrogen In The Yihe River Basin Based On GWR

The Yihe River Basin is an important ecological function zone as part of the South-Northtransitional belt in China.Previous studies in the region have focused on hydrological characteristics and landscape patterns,and lacked exploration of soil carbon and nitrogen.Therefore,based on experimental data,this paper studied the characteristics of soil carbon and nitrogen content using classical statistical analysis and multiple stepwise regression analysis.At the same time,Geographical weighted regression tools in GWR4.0 and Arc GIS were used to analyze the spatial characteristics of soil carbon and nitrogen and their influencing factors,To provide theoretical guidance for the scientific use of regional land.Mainly draws the following results:(1)In 0-20 cm,the average contents of soil organic carbon,total nitrogen,active organic carbon,nitrate nitrogen and ammonium nitrogen were 13.30 g.kg-1、0.30 g.kg-1、3.82 g.kg-1、19.74 mg.kg-1、11.11 mg.kg-1,In 20-40 cm,the average content of soil organic carbon,total nitrogen,active organic carbon,nitrate nitrogen and ammonium nitrogen were 8.21 g.kg-1、0.20 g.kg-1、2.08 g.kg-1、11.53 mg.kg-1、13.38 mg.kg-1;The content of soil organic carbon,active organic carbon,soil total nitrogen and nitrate nitrogen were higher than 20-40 cm in 0-20 cm,while the content of ammonium nitrogen was lower than 20-40 cm;The soil carbon and nitrogen variability was moderate.The overall coefficient of variation of soil nitrogen was greater than that of soil carbon.On the soil profile,the decline of organic carbon was greater than that of active organic carbon.The decreasing order of soil total nitrogen and its components was in the order of nitrate nitrogen> total nitrogen> ammonium nitrogen.The characteristics of soil carbon and nitrogen under the influence of land-use types and soil p H conditions were analyzed.The content of soil organic carbon,active organic carbon,and total nitrogen in woodlands and shrubs in 0-20 cm were higher than those in cultivated land and orchards.The content of nitrate nitrogen and ammonium nitrogen is higher in cultivated land and orchard than in forest land and shrubs.The content of soil organic carbon,nitrogen and its components in 20-40 cm arable land was higher than that in the forest land and shrub-grass tussock.In0-20 cm and 20-40 cm,the contents of soil organic carbon,active organic carbon and total nitrogen inneutral and acidic soils were higher than that in alkaline soils,and the contents of strong alkaline soils were the lowest.The order of ammonium nitrogen content is: strong alkaline soil> alkaline soil> neutral and acidic soil.(2)The results of multivariate stepwise linear regression analysis showed that soil organic carbon had more significant effects on soil total nitrogen,active organic carbon,nitrate nitrogen,and ammonium nitrogen at 0-20 cm.At the same time,soil total nitrogen and active organic carbon have significant effects on soil organic carbon.At 20-40 cm,the relationship between soil carbon and nitrogen changed,and the relationship between carbon and nitrogen was more closely related to their respective components.Nitrate and active organic carbon were the main factors affecting soil organic carbon.Organic carbon and total nitrogen are the key factors affecting nitrate nitrogen.(3)The application of GWR model and the selection of factors affecting soil carbon and nitrogen.Using soil organic carbon and nitrogen and their components as dependent variables,Pearson’s bivariate correlation analysis and multicollinearity test were used to screen independent variables to construct a GWR model.0-20 cm,the factors affecting soil organic carbon and active organic carbon are soil total nitrogen,nitrate nitrogen,ammonium nitrogen,altitude,bulk density,50-250μm and manganese.The factors affecting soil organic carbon and total nitrogen are active organic carbon and bulk density.The factors affecting soil total nitrogen and its components are soil organic carbon and active organic carbon.The factors that affect inorganic nitrogen are soil organic carbon,active organic carbon,altitude,p H,1-5μm,5-10 μm,and 50-250 μm.The factors affecting soil active organic carbon,nitrate nitrogen,and ammonium nitrogen are soil organic carbon,altitude,p H,and 50-250 μm.20-40 cm,the relationship between soil organic carbon and active organic carbon is closely related.Total soil nitrogen was mainly affected by organic carbon,nitrate nitrogen,and ammonium nitrogen,while nitrate nitrogen and ammonium nitrogen had significant correlations with total nitrogen,p H,and calcium.The results of the global regression model and local regression model of soil organic carbon and nitrogen and their components showed that the GWR model was more advantageous than the OLS model,and its four indicators of RSS,AICc,R2,and Adj-R2 were superior OLS model.(4)Soil carbon and nitrogen spatial distribution forecast results show:0-20 cm,the distribution of soil organic carbon,active organic carbon,and total nitrogen were relatively uniform.Most of the highvalue areas were concentrated in the upper reaches of forest lands,and the low value areas were mainly located in areas where construction land was dense.Nitrate in the upper reaches of the forest consistent with the distribution of soil total nitrogen,but in the middle and lower reaches of the difference.The high value area of ammonium nitrogen is in the middle and lower reaches of the farming area,and the content of ammonium nitrogen in the woodland area is lower.20-40 cm,the high-value areas of soil organic carbon,active organic carbon,total nitrogen,and nitrate nitrogen migrated downstream,and the downstream became a high-value concentration area.Ammonium nitrogen has become a high value zone in the middle reaches,and has become a low value zone upstream and downstream.The prediction accuracy of soil organic carbon and active organic carbon in 0-20 cm and 20-40 cm increased with elevation.Local R2 distribution of total nitrogen and nitrate nitrogen in 0-20 cm soil decreases from upstream to downstream,and local R2 distribution trend of ammonium nitrogen is just opposite to soil total nitrogen.The local R2 value of 20-40 cm soil total nitrogen has two distinct high value areas.One is an area with an elevation of more than 1000 m,and one is an area with an elevation of about 200 m,while the Local R2 value is relatively small in the range of 300-1000 m.In general,the distribution trends of soil organic carbon,active organic carbon and total nitrogen were consistent.The distribution of soil total nitrogen and nitrate nitrogen was consistent in the upper reaches of the forest.The interference in the middle and lower reaches of the basin was due to human factors,nitrate nitrogen and ammonium.The distribution of nitrogen is different from soil total nitrogen.