岷江上游土壤侵蚀时空演变特征及其成因分析

Spatiotemporal Dynamics of Soil Erosion and Associated Influencing Factors in the Upper Minjiang River Watershed

为研究岷江上游流域土壤侵蚀动态变化情况,使用通用土壤流失方程(USLE)和统计学、空间分析等方法探讨了该区域2001—2017年土壤侵蚀时空演变特征及其成因。结果表明:(1)岷江上游流域土壤侵蚀主要发生在西部、西南部、东北部和东南部。(2)土壤侵蚀模数显著减小区域主要分布在流域西部和西南部,从地形、降水和土地利用看,主要分布于海拔2500~5000 m、坡度大于15°、年均降水量800~1200 mm的区域和林地侵蚀区。土壤侵蚀显著增加区域主要分布在北部和东南部,其中以中山、亚高山区域和年均降水量400~800 mm的干旱河谷区域为主。(3)土壤侵蚀状况与海拔、坡度、年降水量和植被类型在空间上呈显著正相关关系(p<0.05),随着海拔、坡度、年降水量增加,土壤侵蚀现象越明显。(4)未利用地、草地和林地土壤侵蚀较明显,侵蚀占比(轻度及以上侵蚀面积占该类型的比例)分别为87.11%,39.75%和9.49%。(5)不同类型林地侵蚀占比由大到小为疏林地(15.04%)>针叶林(13.50%)>混交林(4.41%)>阔叶林(0.97%)。林地土壤侵蚀主要受降水和植被覆盖度影响;而灌木和草地土壤侵蚀主要受制于降水。综上,未来该区域生态恢复需要重点加强对高海拔带(>2500 m)、坡度大于25°以及草地区域的植被恢复研究,进一步提高各类型植被水源涵养功能,开展流域土壤侵蚀分类治理,提高区域土壤侵蚀防治效果。

The Universal Soil Loss Equation(USLE),statistical and partial correlation analysis were used to examine the spatiotemporal evolution and causes of soil erosion in the upper Minjiang River watershed from 2001 to 2017 in order to understand the dynamic change of soil erosion in this region.The results showed that:(1)soil erosion mainly occurred in the west,southwest,northeast,and southeast of the study area;(2)the areas with significant decrease of soil erosion mainly distributed in forestlands and the areas with the elevation from 2500~5000 m,slope gradient greater than 15°and annual precipitation of 800~1200 mm in the west and southwest;the areas with significant increase of soil erosion mainly distributed in the north and southeast of the study area;(3)soil erosion was positively correlated with altitude,slope gradient,annual precipitation,and vegetation types(p<0.05);(4)the soil erosion mostly distributed in undeveloped land,grassland,and woodland,and the erosion rates(the proportion of area of erosion classified as mild and above to each land use type)were 87.11%,39.75%,and 9.49%,respectively;(5)the contributions of soil erosion intensities of or sparse woodland,coniferous forest,mixed forest,and broad-leaved forest to total erosion intensity were 15.04%,13.50%,4.41%,and 0.97%respectively;soil erosion in woodland was mainly affected by precipitation and vegetation coverage while that in shrub and grassland was mainly affected by precipitation.In conclusion,the soil erosion in the upper Minjiang River watershed had the distinct spatial and temporal variation,which was mainly determined by precipitation,topography and vegetation type.These findings can benefit the design of soil erosion control practices to protect natural environment in the upper Minjiang River watershed according to graphic and vegetation types.