紫色土和黄壤土壤可蚀性动态变化机制及其定量表征

Knowledge of soil erodibility is an essential requirement for erosion prediction. Selection of suitable assessing indicators of soil erodibility and its accuracy estimating, greatly impact the reliability of soil erosion predication. However, due to the complex affecting factors of soil erodibility, current knowledge and practices on soil erodibility do not meet the needs for establishment of soil erosion predication model. Although few studies had proved the temporal variation of soil erodibility, divergences still remained in their results. Whereas, at present, the mechanism of soil erodibility dynamical changes and its key factors were not clear yet, which need further and sustematic study. This study, therefore, selected the serious eroded area of the purple soil and the yellow soil as research sites. The combined methods of field investigation, on-site monitoring and measurement, laboratory analysis, and rainfall simulation were used in this study. Meanwhile, the long-term observed data from runoff plots during 2002-2013 is adopted. Based on the analysis of the key soil erodibility factors, interannual and seasonal variations of soil erodibility were vertified; the intrinsic mechanisms and variation characteristics of soil erodibility key indicators, which caused by the potential divers (e.g., dry-wet cycles, seepage effect and soil organic matter changes), were exposited; and then the machenism of soil erodibility dynamical changes were proposed and quantified. The results will not only deep the study of soil erodibility machanism, but also provide scientific basis to develop soil erosion predication model; as well as provides scientific support for protecting the valuable purple soil and yellow soil resources in the upper reaches of Yangtze river.

土壤可蚀性是侵蚀预报的基础研究内容，能否筛选出适宜的指标体系和准确的估算土壤可蚀性，直接影响侵蚀预报模型的可靠性及其结果的可信度。国内外部分研究已证实土壤可蚀性动态变化现象的存在，但影响土壤可蚀性动态变化的关键因子及内在机制尚不清楚，无法满足土壤侵蚀精准预报和侵蚀机理研究的需要，亟待深入系统的研究。为此，本研究以长江上游地区侵蚀严重的紫色土和黄壤为研究对象，在2002-2013年长序列观测资料的基础上，采用野外调查、定位动态监测、室内分析与模拟、人工模拟降雨相结合的方法，通过明晰土壤可蚀性各因子间的相关关系、作用途径和强度，筛选出土壤可蚀性关键因子；探明研究区主要潜在驱动因素（土壤有机质、干湿交替和壤中流）对土壤可蚀性关键因子的作用影响；进而揭示和量化土壤可蚀性动态变化机制。研究结果将深化土壤可蚀性机理研究，为侵蚀预报模型研发提供重要的理论基础，并为长江上游地区水土流失治理提供科学依据。

开展土壤可蚀性动态变化机制及其量化表征的研究，不仅能深化对土壤侵蚀过程机理的认识，也可为侵蚀预报模型的建立提供理论基础和科学依据。由于土壤可蚀性影响因素的复杂性和不确定性等特点，导致其动态变化的关键影响因子及内在作用机制尚不清楚，无法满足土壤侵蚀精准预报和侵蚀机理研究的需要。本项目以长江中上游侵蚀严重区的主要土壤类型为研究对象，采用野外调查、定位动态监测与测定、室内分析与模拟、人工模拟降雨试验等相结合的综合研究方法，并在以下5个方面取得研究进展：1）确定了影响土壤可蚀性动态变化的关键影响因子及其主要表征指标；2）量化了干湿交替、土壤有机质变化和近地表水文条件等驱动因素作用对土壤可蚀性关键影响因子的动态变化影响；3）提出了不同近地表水文条件对细沟间和细沟临界土壤可蚀性的作用贡献，并修正了WEPP模型中细沟可蚀性和细沟间可蚀性的计算方法；4）明晰了雨型驱动下的坡面侵蚀过程响应关系及其对侵蚀模式转变的激发作用；5）建立了适用于我国的土壤可蚀性的Dg-OM算法，并给出了我国主要水蚀区土壤可蚀性K值图。项目执行3年来，较圆满的完成了各项研究任务和考核目标：1）发表论文7篇（其中SCI和EI论文5篇），参编专著2部，获批软件著作权登记3项；2）联合培养博士后1名，研究生6名（博士生3名，硕士生3名）；3）对研究成果进行了广泛的学术交流，参加国际和国内会议各4人次；4）基于雨型驱动的土壤侵蚀机理研究相关成果被美国农业部农业研究服务局国家草地实验室（USDA-ARS GRL）应用。项目研究结果为土壤侵蚀过程机理和土壤侵蚀定量预报研究带来了新的突破，同时为长江上游严重土壤侵蚀区水土流失治理提供科学依据。