基于RUSLE和地理探测器模型的西南地区土壤侵蚀格局及定量归因

Spatial Soil Erosion Patterns and Quantitative Attribution Analysis in Southwestern China Based on RUSLE and Geo-Detector Model

基于RUSLE模型和GIS技术,利用1982~2013年西南地区的月尺度降水、GIMMS NOAA/AVHRR NDVI数据及有关的土壤(机械组成和有机碳)和DEM资料,探究西南地区侵蚀强度的分布格局,识别高侵蚀强度(热点)区域的区位特征;依据地理探测器模型,开展识别区域和热点尺度下影响土壤侵蚀强度分布格局的主导因素和度量交互耦合程度的定量归因研究.结果表明:(1)1982~2013年期间,西南地区保持能力达到7.37,由东到西逐渐降低;实际土壤侵蚀模数为25.77t·hm^(-2)·a^(-1),属于中度侵蚀,呈现出东西弱中部强的分异特征,侵蚀热点区域为藏东南-横断山区、四川盆地-川西高原过渡带、云贵高原的乌蒙山区和桂北丘陵区.(2)灌丛和高山植被是影响土壤侵蚀的主要植被类型;15°~35°的坡度、3000~5000m的海拔、30%~45%的植被盖度和400~800mm的年降水梯度区域的侵蚀强度指数均大于2,是土壤侵蚀主要发生源地.(3)西南地区多个因素中,坡度起着绝对主导作用,定量归因在39.17%~78.34%之间;两两因素之间交互协同作用表现为非线性增强或者相互增强,坡度和盖度交互作用最大.研究涉及到的整个西南区域,侵蚀强度分布格局是坡度、海拔和盖度综合作用的结果;热点区域水平上,海拔跨度相对较小,主要受盖度和坡度的影响.因此,西南地区在制定和实施土壤侵蚀防治与生态恢复政策时,应优先考虑坡度在15°~35°且植被盖度在30%~45%的区域.

The spatial patterns of erosion intensity in southwestern China(SW)were determined using the RUSLE model and GIS technology based on the monthly precipitation,GIMMS NOAA/AVHRR NDVI data,soil(particle size distribution and organic carbon)and DEM data from 1982 to 2013,and the characteristics of high intensity hotspots were identified.The Geo-Detector model was used to identify the quantitative attributions of the dominant factors affecting the regional and hotspot distribution pattern of soil erosion intensity,and to measure the degree of interactive couplings among the factors.Results showed that:(1)During 1982~2013,the soil conservation capability reached 7.37,decreasing gradually from east to west.The actual erosion intensity was 25.77 t·hm^(-2)·a^(-1),as moderate erosion,and showed the differential features of the weak east and west parts and a strong central part.The high erosion intensity hotspots were mainly concentrated in the southeastern Tibet-Hengduan Mountains transition zone,the Sichuan Basin-Western Sichuan Plateau transition zone,the Wumong Mountains in the Yunnan-Guizhou Plateau,and the hilly region of northern Guangxi.(2)Shrubs and alpine vegetation were the main vegetation types affecting soil erosion.In areas with 15°~35°slope,3000~5000 m altitude,30%~45%vegetation cover,and 400~800 mm precipitation,the erosion intensity indexes were greater than 2;these areas were the major sources of soil erosion occurrence.(3)Among the multiple factors in SW,slope played the most prominent role,with its quantitative attribution to soil erosion pattern ranging from 39.17%to 78.34%.The interactive effects among any two factors were shown as either nonlinear enhancement or mutual enhancement,with the interaction between slope and coverage being the greatest.In the entire SW covered in this study,the distribution patterns of erosion intensity were the results of combined effects of slope,altitude and vegetation cover;at the level of hotspots,the effects mainly resulted from slope and vegetation cover because of relatively small elevational range.Therefore,when formulating and implementing soil erosion prevention and ecological restoration policies,the areas with 15°~35°slope and 30%~45%vegetation cover should be targeted as the priority.