Spatial Distribution Characteristics And Influencing Factors Of Soil Organic Carbon In Huma River Basin

Soil organic carbon is a kind of carbon containing organic compounds existing in soil in various forms,which has an important impact on the global carbon cycle.As an important part of global terrestrial carbon pool,frozen soil organic carbon pool,even if it changes slightly,may also lead to significant changes in atmospheric CO₂concentration.Therefore,it is of great significance to master the content of soil organic carbon and its influencing factors in permafrost regions for understanding the budget of soil organic carbon in permafrost regions in cold regions and its response to climate warming.Based on this,this study selected the Huma River Basin as the research object,and used geostatistics to analyze the spatial variability of soil organic carbon in different types of permafrost regions in the Huma River Basin;Using correlation analysis and redundancy analysis to explore the influencing factors of soil organic carbon content in the Huma River Basin;The least square method model,geographical weighted regression model and random forest model were constructed to verify the accuracy and evaluate the applicability of the model;Simulate and analyze the main factors that affect the spatial distribution characteristics of soil organic carbon.The results show that:（1）The range of soil organic carbon content of 0-20 cm in the entire Huma River Basin is between 14.75 and 184.95 g/kg,with a coefficient of variation of 0.68,showing a moderate degree of variation overall.From the perspective of different permafrost types,the soil organic carbon content in the three permafrost regions belongs to the medium variation degree.The variation degree of soil organic carbon content in different permafrost regions is in the order of discontinuous permafrost region>sporadic permafrost region>island permafrost region.（2）The annual average temperature in the Huma River basin has a significant impact on the soil organic carbon content of 0-20 cm（P<0.01）.With the decrease of temperature,the soil organic carbon content showed an increasing trend;The soil organic carbon of 0-20 cm in the Huma River basin is significantly affected by the annual precipitation,altitude,and climate humidity index（P<0.01）.The soil organic carbon content increases with the increase of annual precipitation and altitude;Slope has a significant impact on the soil organic carbon content of 0-20 cm soil layer（P<0.05）,and the soil organic carbon content gradually increases with the increase of slope.According to the redundancy analysis,the climate humidity index is collinear,so the annual average temperature,annual average precipitation,altitude and slope are selected as the influencing factors of soil organic carbon in the Huma River basin.（3）By comparing the simulation accuracy of soil organic carbon content in the Huma River Basin using the model,it was found that selecting different spatial weight functions would affect the prediction accuracy of the GWR model.The selected spatial weight function was Fixed Gaussian.Comparative analysis of the accuracy of soil organic carbon prediction in the Huma River Basin using different models,where R²values are compared as follows:GWR>OLS>RF;RMSE value comparison:GWR<OLS<RF;Comparison of MAE values:GWR<OLS<RF.It fully indicates that the simulation effect of GWR model is better than that of RF model and OLS model.Due to the fact that the GWR model more accurately reflects the local situation in the spatial prediction of soil organic carbon content in the Huma River Basin,it is more suitable for predicting the spatial distribution characteristics of surface soil organic carbon in the Huma River Basin.（4）The spatial distribution characteristics of soil organic carbon in 0-20 cm surface layer of permafrost region in Huma River basin were simulated by the model.The soil organic carbon content was between 5.05-157.81 g/kg.The spatial distribution of soil organic carbon content in the study area generally showed a trend of decreasing from west to east.The soil organic carbon content in discontinuous permafrost region was on the high side,and the low value was mainly distributed along the river banks and in valleys.The distribution trend of soil organic carbon content in sporadic permafrost regions decreases gradually from south to north.The soil organic carbon content in island permafrost area is low as a whole.（5）Further analysis found that the spatial distribution pattern of soil organic carbon in the permafrost region of the Huma River basin and the elevation and slope of the terrain factors had a relatively consistent distribution pattern;The comprehensive effect of climate factors,annual average precipitation and annual average temperature,affects the spatial distribution of soil organic carbon in the permafrost region of the Huma River basin,and the absolute value of annual average temperature is the largest among various influencing factors,which plays a more important role in the spatial distribution of soil organic carbon in the Huma River basin.