Table1_Quantifying the spatial flow of soil conservation service to optimize land-use pattern under ecological protection scenarios.docx

Land use pattern optimization is an effective approach for sustaining soil conservation service (SCS) under the influence of climate change and anthropogenic activities across the Loess Plateau of China. However, current studies establish ecological protection scenarios (EPSs) for land-use optimization based on the transfer matrix of EPS alone, which ignores the important role of scientific intervention by human beings on land-use patterns. To fill this knowledge gap, the Wuding River watershed was employed as the research object, and land use under three EPSs was simulated according to the transfer matrix, dry-wet zoning, slope, and soil and water loss zoning. The quantity of SCS and its spatial flow and benefit under different climate scenarios were then simulated and compared with those under natural development scenarios (NDSs). SCS was found to decrease due to the expansion of urban areas and agriculture under the NDSs and increase under the EPSs relative to the NDSs. In addition, under the EPSs, SCS restricted to dry-wet zoning exhibited no significant advantage over those without additional constraints. However, when complex constraints, such as dry-wet zoning, slope, and soil and water loss zoning, were combined, SCS was significantly improved in areas with large topographic fluctuations. Further, compared with that in 2000–2020, the benefit of SCS in future scenarios displayed an increasing trend in the direction of the mainstream. Owing to the cumulative benefit, when the spatial flow of the SCS upstream decreases with urban expansion, the benefit for the downstream area, which is provided by land-use optimization, will decrease. Overall, our findings provide a framework for land use optimization by incorporating ecosystem service flow, ultimately facilitating land management, ecological restoration, and soil erosion prevention.

土地利用格局优化是在中国黄土高原（Loess Plateau）地区应对气候变化与人类活动影响、维持土壤保持服务（soil conservation service, SCS）的有效路径。然而，当前研究仅依托生态保护情景（ecological protection scenarios, EPSs）的转移矩阵构建土地利用优化的生态保护情景，忽略了人类科学干预对土地利用格局的重要作用。为填补该研究空白，本研究以无定河流域（Wuding River watershed）为研究对象，基于转移矩阵、干湿分区、坡度与水土流失分区，模拟了三种生态保护情景下的土地利用格局。随后，本研究模拟了不同气候情景下的土壤保持服务量及其空间流动与效益，并与自然发展情景（natural development scenarios, NDSs）的对应结果进行对比。研究结果显示，自然发展情景下城镇与农业用地扩张会导致土壤保持服务水平下降，而生态保护情景下的土壤保持服务相较自然发展情景有所提升。此外，仅受干湿分区约束的生态保护情景，其土壤保持服务相较于无额外约束的情景并无显著优势；但当结合干湿分区、坡度与水土流失分区等复合约束条件时，地形起伏较大区域的土壤保持服务得到显著改善。进一步对比2000-2020年基准时段，未来情景下土壤保持服务的效益沿干流方向呈上升趋势。受累积效益影响，当上游土壤保持服务的空间流动因城镇扩张而减少时，土地利用优化为下游地区带来的效益将随之降低。总体而言，本研究提出了纳入生态系统服务流的土地利用优化框架，可为土地管理、生态修复与水土流失防治提供科学参考。