基于土壤团聚体分形维和径流能耗分析的土壤可蚀性定量表征

The soil erosion process has a close relationship with the soil aggregates size distribution and stability. It is quite important to analyse the coupling mechanism of soil aggregates structure characteristic and soil erodibility for comprehensive soil erosion process prediction. Quantitative analysis the relationship between soil structure characteristic and soil erosion process is helpful for deepening the soil erosion mechanism research. Former studies on soil erodibility were less from the point of erosion dynamic process,and the relationship between the soil aggregates structural characteristics and erodibility was not achieved a truly quantitative assessment. Taking the main soil types of the most serious erosion regions in China as the research object, this project aims at studying the relationship between the sediment yield, runoff energy consumption and rainfall energy, using flow scouring experiment and rainfall stimulating experiment under different flow discharges and different rainfall intensities. Based on the fractal dimension theory and field soil sample collecting and measuring, the validity of soil aggregates fractal dimension calculation using liner and nonlinear method will be evaluated. On the above research basis, the simulation conversion model of the soil erodibility and soil aggregates fractal dimension will be established and verified by experimental data. This project is expected to provide theoretical basis for quantify the soil erodiblity research and discuss the mechanism of soil erosion process and the soil erosion prediction model building.

土壤侵蚀过程与土壤团聚体的粒径分布和稳定性关系密切，开展土壤团聚体结构特征与可蚀性耦合机理研究，并就二者关系进行探讨，对深化土壤侵蚀机理研究十分重要。针对以往关于土壤可蚀性的研究较少从侵蚀动力过程角度进行，土壤团聚体结构特征与可蚀性间的关系未实现真正定量化等问题，本研究以我国主要水蚀区（东北黑土区、西南紫色土区、黄土高原区、南方红壤区）土壤为研究对象，采用放水冲刷实验和人工模拟降雨实验，阐明坡面侵蚀产沙与径流能耗、降雨动能间的关系，提出基于径流能耗的土壤可蚀性定量表达；结合野外现场土样采集、分析测试，基于分形理论，探讨不同土壤类型团聚体具有分形特征的粒径区间，评价线性和非线性两种拟合方式计算土壤团聚体分形维的有效性；在上述研究基础上，建立土壤可蚀性与团聚体分形维间的转化模型，并用实验数据加以验证，以期为侵蚀预报模型中可蚀性参数的确定及区域尺度土壤可蚀性的估算提供依据。

土壤侵蚀过程与土壤团聚体的粒径分布和稳定性关系密切，开展土壤团聚体结构特征与可蚀性耦合机理研究，并就二者关系进行探讨，对深化土壤侵蚀机理研究十分重要。本研究以我国主要水蚀区（东北黑土区、西南紫色土区、黄土高原区、南方红壤区）土壤为研究对象，采用放水冲刷实验和人工模拟降雨实验，阐明了坡面侵蚀产沙与径流能耗、降雨动能间的关系，提出了基于径流能耗的土壤可蚀性定量表达，并建立了土壤可蚀性与团聚体分形维间的转化模型。研究得出如下主要结论：.（1）干筛团聚体分形维数与＜0.25mm粒径的团聚体含量显著正相关，湿筛水稳性团聚体分形维数与＜0.25mm粒径的水稳性团聚体含量显著正相关。水稳性团聚体分形维数可用来评价土壤水稳性。（2）选取以往研究中的土壤可蚀性评价指标进行主成分分析，得到最佳指标体系：有机质含量、水稳性团聚体分形维数、水稳性团聚体平均重量直径、＞0.5mm水稳性团聚体含量、物理性粘粒含量、分散系数六种指标，其中，水稳性团聚类因子贡献率最大。（3）在分析四种主要侵蚀性土壤（红壤，紫色土，黑土和黄绵土）的团聚体粒径分布的基础上，计算了上述四种土壤类型的重量平均直径（MWD）、几何平均粒径（GMD）、分形维（FD）和团聚体稳定性指数（ASI）。结合不同雨强和不同坡度条件下的人工模拟降雨实验，阐明了四种土壤类型的细沟间可蚀性随坡度、雨强的变化规律，分析了各种不同土壤团聚体稳定性指标与细沟间可蚀性的关系。除分形维（FD）与细沟间可蚀性呈正相关外，其余3个指标均与细沟间可蚀性呈负相关。相比较而言，土壤团聚体的稳定性指数（ASI）、几何平均粒径（GMD）比分形维（FD）和重量平均直径（MWD）与土壤细沟间可蚀性的关系更紧密。（4）地表径流主要与土壤团聚体组成及分形特征有关，侵蚀产沙主要与团聚体水稳性有关，湿筛水稳性团聚体的分形维数能较好的描述地表土壤侵蚀强度。经过定量比较水稳性团聚体分形维数与侵蚀率的关系，建立了坡面侵蚀产沙预测模型。