淤地坝赋存信息解译黄土高原小流域土壤侵蚀特征演变及驱动机制

Based on the drastic change of erosion environment on the Loess Platuea and of water and sediment in Yellow river, it is necessary to reveal the changes of soil erosional characteristics in small catchments, they response to the variation of erosion environment and its driving mechanism, especailly to vegetation recovery. However, the research progress of these parts have been slowly because of the research method limitation. In this project, the methods of GIS/RS and compound fingerprinting technique will be used to excavate the soil erosion information which kept in the sediments in the check dams. The variations of sediment yeild from small catchments will be analyzed and described. The sources of sediments in the checkdams will be indentified. The contribution of different sediment sources will be uncovered. The erosional characteristic of extreme rainfall will be scientifically studied. Combining the periodical variations of the factors of erosion enviromment, the responsive relationships between the variations of the erosion characteristics and erosion enviroment in small catchments will be analyzed. The contribution percentages of the effects of anthropogenic and natural factors on soil eroison in small catchments will be quantified. The driving mechanism of the variation of soil erosion in small catchments will be revealed. This project is very important to assess the governance effect of small catchments in the Loess Plateau, to confirm the governance plan in the future, to discover the driving mechanism of the drastic changes of water and sediment in Yellow river, and to maintain the health of Yellow river.

在黄土高原土壤侵蚀环境和黄河水沙巨变的大背景下，黄土高原不同侵蚀区小流域土壤侵蚀特征演变及对生态恢复的响应和驱动机制是亟待解决的科学问题，但因传统研究方法的局限，这方面研究进展缓慢。本项目拟以黄土高原不同侵蚀区典型淤地坝及坝控小流域为研究对象，以复合指纹识别和GIS/RS技术为手段，基于淤地坝沉积泥沙赋存的小流域侵蚀信息，系统研究小流域侵蚀强度的时空变化，确定淤地坝沉积旋回的泥沙来源，揭示小流域泥沙来源的时空演变，突出极端降雨事件下小流域侵蚀产沙特征及在不同生态恢复期的变化，并结合侵蚀环境因子的阶段性变化，分析小流域侵蚀产沙特征与侵蚀环境演变的响应关系，定量辨析人为因素和自然因素对小流域侵蚀特征变化的贡献，揭示黄土高于不同侵蚀区小流域侵蚀产沙特征演变的驱动机制。该项目的研究对评价现有黄土高原治理效果、确定未来治理方略、揭示黄河水沙巨变的驱动机制及保障黄河健康运行都具有非常重要的意义。

在黄土高原土壤侵蚀环境和黄河水沙巨变的背景下，黄土高原小流域土壤侵蚀特征演变及对生态恢复的响应和驱动机制是亟待解决的科学问题。项目采用复合指纹识别、GIS/RS相结合的方法，研究黄土高原不同侵蚀区域五个代表性坝控小流域的侵蚀特征与泥沙来源的时空演变特征，结合日降雨资料、淤地坝运行历史、主要人为活动的分析揭示土壤侵蚀特征演变的驱动机制。研究发现（1）黄土高原不同区域小流域侵蚀产沙均具有明显的阶段性变化特征。淤地坝沉积旋廻泥沙量和降雨量的双累积曲线变化，代表性化学计量参数均可将各淤地坝的产沙速率划分为3-4个阶段。（2）淤地坝运行期间，沟壁均为各侵蚀区小流域主要泥沙源地，坡耕地是重要泥沙源地。在一般侵蚀性降雨和大暴雨条件下泥沙贡献率存在显著差异，大暴雨条件下，重力侵蚀明显，小流域侵蚀泥沙量高达一般侵蚀性降雨条件下的约26倍。（3）从南到北，黄土高原小流域沟谷地产沙的贡献逐渐增大，从延安到榆林再到神木，代表性小流域（胡家湾，埝堰沟和老爷满）沟谷地和沟间地的泥沙贡献比约从6:4增加到7:3再到8:2。（4）采用霍洛特公式依据降雨及反应土地利用变化敏感的土壤C,N,P化学计量参数（N和C:P）定量区分了各流域自然和人为因素对侵蚀产沙的影响，结合降雨变化特征，表明降雨和土地利用方式是影响小流域侵蚀强度和泥沙来源的主要因素。降雨雨型对流域侵蚀产沙特征直接相关，而土地利用方式主要通过退耕还林（草）等工程及不合理的土地利用、煤矿开采等方式抑制或促进流域侵蚀产沙。本项目基于淤地坝沉积泥沙赋存的信息阐明了坝控流域的土壤侵蚀变化特征，定量辨析自然和人为因素对小流域侵蚀产沙的影响，对明确黄土高原侵蚀环境巨变背景下，不同侵蚀区域的侵蚀特征及其驱动机制具有重要意义，为评价黄土高原的治理成效，确定未来的治理方略提供了科学依据。