南方山区弱发育土壤水文过程与侵蚀动力机制

Soil architectures such as soil texture, structure, soil layering and soil-parent material (or bedrock) interface, play an important role on soil hydrological and erosion processes . Among those factors that influence water flow, soil layering is a significant factor because changes in soil texture, density, or structure across the boundary of two adjacent layers could considerably alter water flow direction and soil moisture distribution. The Primarosols wildly distributed in steep slope of mountain areaes in the south China often have special soil architectures: shallow soil layer and A-C or A-R profile. For those soils, poor soil structure and soil- parent material (or bedrock) interface significantly impact the soil hydrologic process such as infiltration, surface runoff, subsurface flow and bedrock flow，furthermore alter the erosion processes. To understand the effect of shallow soil layer and special interface between soil and parent material （bedrock）on soil hydrological and erosion processes，three soils derived from purple Sandstone、Shale and Granite will be choose for different parent material and soil—material（bedrock）interface. The soil profile hydraulics properties and the infiltration、water redistribution process will be investigated in infiltration experiments. And under in situ rainfall simulation experiments, the runoff and erosion process and characteristics also will be studied to explain the effects of those special soil architectures on soil hydrological and erosion dynamic mechanism of the steep sloping lands. This research is important to understand the erosion mechanism of mountain area in the south of China.

弱发育土壤是我国南方山区常见土壤，多分布于植被覆盖稀疏、土壤侵蚀严重的山区中上部。这类土壤往往处于成土初始阶段，土壤层较薄且剖面层次为A-C或A-R土体构型。土壤的母质性特征及“上覆土壤、下伏岩石（母质）”的二元结构使其有着特殊的坡面水文过程和侵蚀过程。本项目拟以发育我国南方山区的紫色砂岩、页岩和花岗岩母质上的弱发育土壤为研究对象，通过野外考察和长期观测，室内外模拟降雨实验，比较研究不同土壤剖面构造及土壤/母质（母岩）界面对山区弱发育土壤降雨入渗、产流等水文过程的影响。明确土壤剖面结构特征及岩土界面对土壤坡面侵蚀过程的影响，阐明陡坡弱发育土壤剖面层次结构及土壤母质（母岩）界面在坡面水沙传递中的动力学机制。该研究对于了解南方陡坡地区弱发育土壤侵蚀机制和防治有重要意义。

弱发育土壤是我国南方山区常见土壤，多分布于植被覆盖稀疏、土壤侵蚀严重的山区中上部。这类土壤往往处于成土初始阶段，土壤层较薄且剖面层次为A-C或A-R土体构型。土壤的母质性特征及“上覆土壤、下伏岩石（母质）”的二元结构使其有着特殊的坡面水文过程和侵蚀过程。本项目以发育我国南方山区的紫色砂岩、页岩和花岗岩母质上的弱发育土壤为研究对象，通过野外考察和长期观测，室内外模拟降雨实验，比较研究不同土壤剖面构造及土壤/母质（母岩）界面对山区弱发育土壤降雨入渗、产流等水文过程的影响。研究结果表明：弱发育土壤主要分布在流域的中上部，地形比较陡峭的部位，不同母质的弱发育土壤剖面A层厚度分布范围不同，花岗岩弱发育土壤（花岗岩土壤）主要为10-15 cm，页岩弱发育土壤（页岩土壤）土层厚度分布在15-20 cm；紫色砂岩母质弱发育土壤（紫色砂岩土壤）土层厚度范围为3-24 cm。三种土壤均表现出较强的母质特征显著，A层和C层中都有较高的砾石含量，且土壤的颗粒组成差别不明显，整个剖面均具有较高的饱和导水率，C层通气性、入渗性能和持水能力均低于A层土壤；三种土壤中优先流染色路径数均以SPW< 20 mm为主，水分主要通过大孔隙流运移。其中页岩土壤总体入渗深度最浅，A层优先流活跃，C层几乎没有优先流发生。紫色砂岩剖面整体入渗能力都较强， C层优先流发育明显。受土壤母质的影响，A/C层次剖面水力性质差异，三种母质弱发育土壤中产流过程及降雨分配有明显差异：相同降雨条件下，花岗岩土壤土壤蓄水能力最强，但地表径流量最大，页岩土壤具有最高的壤中流量，紫色砂岩发育土壤在重新分配降雨水分方面表现出更高的深层入渗。