黄土高原植被恢复与生态系统土壤保持服务价值增益研究——以延河流域为例

Abstract

为探究黄土高原地区退耕还林（草）工程（1999）实施后植被恢复的生态效益，选择黄土高原延河流域为研究区，利用趋势线分析法、SWAT（Soil and Water Assessment Tool）水文模型和生态系统服务价值评价方法（市场价值法、机会成本法、恢复费用法和影子工程法等），重点分析2000-2015年该区域植被恢复状况及其对土壤保持的作用，并评估生态系统服务价值的提升效应。研究结果表明：（1）退耕还林（草）工程实施后，延河流域植被覆盖均呈增加趋势，植被恢复显著；（2）植被恢复对土壤侵蚀的抑制作用明显。在没有植被覆盖的条件下，土壤极易发生侵蚀，且侵蚀模数大；从该工程实施以来，2001-2014年土壤保持量具有不同程度的增幅，表明多年来流域治理取得一定的成效；（3）流域植被覆盖以中覆盖为主，土壤保持量以低保持为主。不同植被覆盖下土壤保持量存在差异。其中，中低、中、中高覆盖能有效保持土壤；（4）生态系统土壤保持服务价值时空分布特征明显。流域年均（2000-2015）土壤保持服务价值为3.64×10⁸元，生长季月均土壤保持服务价值为6.06×10⁷元，生态系统土壤保持服务价值显著提升。时间尺度上，生态系统土壤保持服务价值受降水因素影响；空间尺度上，流域生态系统土壤保持服务价值空间差异大，具体表现为下游残塬平梁沟壑区最高，上游山地区次之，中游梁峁丘陵沟壑区最低。通过研究延河流域植被恢复状况以及定量评估土壤保持服务价值，不仅阐明了退耕还林（草）工程带来的巨大生态效益，同时也为流域乃至黄土高原的水土流失治理工作提供一定的参考作用。;In order to explore the ecological benefits of vegetation restoration after the implementation of the Grain for Green Project (GFGP) in 1999, this study selected the Yanhe Watershed in the Loess Plateau as the study area. By using the trendline analysis, SWAT (Soil and Water Assessment Tool) Model and the evaluation approach of ecosystem services (including market value, opportunity cost, restoration cost, and shadow project approaches), the paper analyzed the vegetation restoration status and its effect on soil conservation after the implementation of the GFGP, and assessed the effect of ecosystem service value enhancement. The results showed that:(1) since the GFGP was implemented, the vegetation recovery effect has been remarkable, which was specifically reflected in the increasing trend of vegetation coverage in the Yanhe Watershed from 2000 to 2015. (2) The effect of vegetation restoration on soil erosion was obvious. Without vegetation cover, the soil is prone to erosion with the large erosion modulus. Taking 2000 as the base year when the GFGP was implemented, the soil conservation from 2001 to 2014 has increased to varying degrees, indicating that the watershed management has achieved certain outcomes over the years. (3) The vegetation cover in the watershed is dominated by medium vegetation cover, and the soil conservation is dominated by low soil conservation. There are differences in soil conservation under different vegetation cover. Among them, medium-low, medium and medium-high vegetation cover can effectively maintain the amount of soil. (4) The temporal and spatial distribution characteristics of the value of the ecosystem soil conservation services are obvious. From 2000 to 2015, the annual average soil conservation service value of the watershed was 3.64×10⁸ yuan, and the monthly average soil conservation service value was 6.06×10⁷ yuan during the growing season. The value of the ecosystem soil conservation service increased significantly. On the temporal scale, the precipitation is an important factor in the value of the ecosystem soil conservation service; on the spatial scale, the spatial differences in the value of ecosystem soil conservation service in the watershed is large, which is specifically manifested as the highest in the downstream, followed by the upstream, and the lowest in the middle-stream. This study not only clarified the huge ecological benefits brought by the GFGP, but also provided a certain reference role for the soil and water loss management in the watershed and even the Loess Plateau.