基于CSLE-TLSD耦合模型的近40年洞庭湖流域土壤侵蚀时空分异及归因分析

Spatial-temporal Variation and Attribution Analysis of Soil Erosion in Dongting Lake Basin in Recent 40 Years Based on CSLE-TLSD Coupling Model

为了精确模拟洞庭湖流域土壤侵蚀动态过程并定量评估其影响因素贡献,在中国水土流失方程(CSLE)的基础上耦合泥沙输送限制模型(TLSD),实现对土壤分离—搬运—沉积全动态过程分析。在此基础上,采用趋势分析和地理探测器方法探究洞庭湖流域1980—2020年土壤侵蚀时空分异特征与影响机制。结果表明:(1)CSLE-TLSD耦合模型在各水文站的年输沙量模拟值和实测值拟合结果较好(R^(2)=0.56);(2)1980—2020年洞庭湖流域年均土壤侵蚀模数为5.09 t/(hm^(2)·a),侵蚀模数和面积在整体上均呈下降趋势,其中侵蚀显著改善区域占流域总面积的22.60%,而显著加剧区域仅占2.69%;(3)年侵蚀总量以2005年为突变点,呈现出先下降后上升的趋势;(4)2005年前后导致土壤侵蚀变化的主导因子从地类变化转变为年降雨量变化。综上,洞庭湖流域土壤侵蚀总体呈现侵蚀面积收缩、局地恶化的趋势,其中极端降雨事件和经果林开发是侵蚀加剧的主要原因。

In order to accurately simulate the dynamic process of soil erosion in the Dongting Lake basin and quantitatively evaluate its contribution of influencing factors,the sediment transport restriction model(TLSD)was coupled on the basis of the Chinese soil erosion equation(CSLE)to realize the analysis of the whole dynamic process of soil separation-transport-sediment,and trend analysis and geographic detector methods were used to explore the spatial and temporal characteristics and influence mechanism of soil erosion in the Dongting Lake Basin from 1980 to 2020.The results showed that:(1)The simulation and measured values of annual sand transport in each hydrological station were well matched by the coupled CSLE-TLSD model(R^(2)=0.56).(2)From 1980 to 2020,the average annual soil erosion modulus of Dongting Lake Basin was 5.09 t/(hm^(2)·a),and both the erosion modulus and area showed a downward trend on the whole.The areas with significant erosion improvement accounted for 22.60%of total basin area,while the area with significant erosion intensification accounted for only 2.69%.(3)With 2005 as the mutation point,the annual total erosion showed a trend of first decreasing and then increasing.(4)Around 2005,the dominant factor leading to soil erosion change changed from land type change to annual rainfall change.In conclusion,soil erosion in the Dongting Lake basin showed a general trend of erosion area shrinkage,while local deterioration trended,among which extreme rainfall events and fruit forest development were the main reasons for the intensification of erosion.