黄河中游土壤侵蚀时空变化及驱动因素

Temporal and Spatial Changes and Driving Factors of Soil Erosion in the Middle Reaches of the Yellow River

[目的]揭示流域生态工程措施和自然因素对土壤侵蚀演变的影响效应,量化工程因子和水文因子对水土流失的抑制程度,为黄土高原区流域土壤侵蚀综合防治和生态环境质量改善研究提供参考。[方法]基于黄河中游地区77个气象站点降雨数据以及流域内四期土地利用类型、植被覆盖度、数字高程模型、土壤质地等资料,通过提取流域降水、地形、气候、土壤和土地利用等因子,采用RUSEL模型和地理探测器方法,开展了土壤侵蚀时空变化及驱动因素研究。[结果]黄河中游地区2000—2010年侵蚀减幅最显著,在生态工程影响下,海拔1000~1500 m,8°~15°,半阳坡和半阴坡的土壤流失量减少最剧烈;水土流失治理成效表现为林地>草地>耕地,且植被覆盖度30%~50%区间内侵蚀面积变化最剧烈,为退耕还林工程重点恢复重建区。黄河中游多年间降雨呈西北向东南逐渐增加,在地形影响下空间垂直差异会发生变化,年际间呈不显著波动上升趋势,具有加剧土壤侵蚀的潜在条件。植被覆盖度呈线性波动上升的趋势,增量从西北到东南呈递增趋势,植被覆盖度是影响土壤侵蚀的主控因素;黄河中游植被覆盖度与坡度的交互作用影响力最强,且植被覆盖度、坡度与其他因子协同作用可以显著性增强对土壤侵蚀格局演变的作用力。[结论]黄河中游以微度侵蚀为主,多出现在植被发育良好的低海拔地带,中度以上侵蚀出现在黄土高原腹地的粗沙多沙区;黄河中游长期呈农牧为主体的土地利用格局,多年间坡度较陡的耕地不断流向对地形适应性和弹性较高的林草地,反映了国家退耕工程核心一部分是将坡耕地变为林、草地;黄河中游以植被覆盖变化为主要特征的生态工程主导了土壤侵蚀量下降的过程和程度,且任意两种因子交互作用的驱动力均大于单个因子。

[Objective]In order to provide a reference for the thorough control of watershed soil erosion and the improvement of ecological environment quality in the Loess Plateau region,the effects of ecological engineering measures and natural factors on soil erosion evolution were revealed,and the inhibition degrees of engineering factors and hydrological factors on soil erosion were quantified.[Methods]Based on the rainfall data of 77 meteorological stations in the middle reaches of the Yellow River,land use types,vegetation coverage,digital elevation model,soil texture and other data of four periods in the basin,the RUSEL model and geographic detector method were used to study the spatiotemporal changes and driving factors of soil erosion by extracting precipitation,topography,climate,soil and land use in the basin.[Results]The largest reduction in sediment erosion in the Yellow River's middle sections between 2000 and 2010 was observed.Soil loss significantly reduced due to ecological engineering at altitudes between 1000 and 1500 m,at slope gradients between 8°and 15°,and on hillsides that were both semi-shaded and semi-sunny.The capacity of soil and water loss control decreased in the order:forestland>grassland>cultivated land,and the erosion area changed most dramatically in the range of 30%~50%vegetation coverage,which was the key restoration and reconstruction area of the project of converting farmland to forest.In the middle reaches of the Yellow River,rainfall increased gradually from northwest to southeast over the years,and the spatial vertical difference changes under the influence of topography,and the interannual fluctuation increased insignificantly,which had the potential to aggravate soil erosion.Vegetation coverage increased linearly,and its increment increased from northwest to southeast.Vegetation coverage was the main controlling factor affecting soil erosion.In the middle Yellow River,the interaction between vegetation coverage and the slope was the strongest,and the synergistic effects of vegetation coverage,slope and other factors could significantly enhance the force on soil erosion pattern evolution.[Conclusion]In the middle reaches of the Yellow River,the land use pattern was dominated by agriculture and animal husbandry for a long time,and the cultivated land with steep slopes flowed continuously to the forest and grassland with high topographic adaptability and elasticity over the years,reflecting that the core part of the national farmland conversion project is to convert sloping land into forest and grassland.The ecological engineering mainly characterized by vegetation cover change dominated the process and degree of soil erosion reduction in the middle Yellow River,and the driving force of the interaction of any two factors was greater than that of a single factor.