沂蒙山区不同土壤水文条件下坡面侵蚀过程与团聚体破碎的互馈机理

Soil aggregate breakdown is directly relevant to capacity of soil detachment and runoff transport, while erosion force determines soil aggregate breakdown mechanism. Soil moisture is one of the most important factors affecting soil aggregate breakdown and soil erosion,and soil surface water regime embodies distribution characteristic of soil moisture for different topographic positions. So, the study of corresponding mechanism between hillslope soil erosion process and soil aggregate breakdown has important significance for process and mechanism of soil erosion under difference soil surface water regimes. This project takes the cinnamon soil in Yimeng mountainous area as the research object. Rainfall simulation and scouring experiments will be conducted under three soil surface water regimes (free drainage, saturation with rainfall, artesian seepage with rainfall). Soil aggregate breakdown mechanism for rainfall erosion and runoff erosion will be illustrated, and this project will point out the erosion force which makes the most contribution to soil aggregate breakdown. In this project, effects of slaking and raindrop impact on micro-aggregate breakdown will be exploded.This study will clarify the response characteristic of soil erosion process to soil aggregate breakdown induced by slaking and raindrop impact,and establish equations to predict sediment yield under the two above soil aggregate breakdown mechanisms which bases on soil aggregate stability. These results in this project will provide a new idea for study of soil erosion mechanism, and supply theoretical guidance for soil erosion control in Yimeng mountainous area.

土壤团聚体的破碎程度直接关系到土壤分离和径流的搬运能力，而侵蚀营力决定了团聚体的破坏机制。土壤含水量是影响团聚体破碎和土壤侵蚀的重要因子，而土壤水文条件则体现了坡面土壤含水量的空间分布特征。因此，开展不同土壤水文条件下坡面侵蚀过程与团聚体破碎互馈机理的研究对揭示水土流失机理具有重要意义。本项目拟以沂蒙山区褐土为研究对象，基于自由入渗、土壤水分饱和与壤中流三种土壤水文条件，结合室内分析、模拟降雨和冲刷试验，阐明降雨和径流侵蚀下团聚体的破碎机制，明确侵蚀过程中对团聚体破碎最具贡献的侵蚀营力；揭示消散和雨滴打击作用对微团聚体破碎的影响机理，阐明坡面侵蚀过程对消散和雨滴打击作用所引起的破碎机制的响应特征，进而构建这两种破碎机制下基于团聚体稳定性的坡面侵蚀预测方程，以期为坡面侵蚀机理的研究提供新的思路，同时期望在机理层面为沂蒙山区水土流失防治提供理论指导。

不同的破碎机制将会导致坡面侵蚀过程响应的差异，而侵蚀过程中各侵蚀营力对团聚体迁移的贡献不同。土壤含水量是影响团聚体破碎的重要因子，而土壤水文条件体现了坡面不同部位的水分特征。因此，开展不同水文条件下土壤侵蚀与团聚体破碎互作关系的研究，对深入理解土壤侵蚀机理极其重要。本项目以褐土横垄为研究对象，基于三种土壤水文条件，结合室内分析、模拟降雨与冲刷试验，研究了不同湿润速率、雨强、地表处理和供水速率下的产流产沙过程和16个粒径团聚体的迁移。5种湿润速率下，20–50 µm 和 50–100 µm是主要的流失粒级，其流失的增加细沟间阶段主要来自2–5 mm和1–2 mm粒级的破碎，而细沟阶段则来自0.25–0.5 mm、0.5–1 mm和 100–200 µm粒级。控制2–5 mm、1–2 mm和100–200 µm粒级破碎的关键速率为20 mm h-1，而对0.25–0.5 mm和0.5–1 mm则为10 mm h-1。随雨滴打击力的增大，自由入渗条件下各粒径团聚体的流失逐渐增强；土壤饱和条件下，2-5 mm粒级流失的变化幅度逐渐减小，1-2 mm粒级不断增加， <1 mm粒级在细沟间阶段不断增大而细沟阶段呈相反趋势；壤中流条件下， <0.5 mm粒级的变化幅度在细沟间阶段逐渐减小而细沟阶段呈相反趋势，而微团聚体则不断增强。控制大团聚体流失的主要营力在土壤饱和条件下为径流作用，壤中流条件60 mm/h雨强下为径流与雨滴打击的交互作用而90 mm/h雨强下为径流作用。自由入渗条件下，雨滴打击对微团聚体各粒级的迁移起主导作用。土壤饱和条件下，控制50-250 um范围内各粒级流失的主导营力为雨滴打击作用，对<50 um内各粒级60 mm/h雨强下为径流作用，90 mm/h雨强下细沟间阶段是雨滴打击而细沟阶段则为径流作用。壤中流条件60 mm/h雨强下主导<50 um内各粒级流失的营力在细沟间和细沟阶段分别为交互和径流作用，而50-250 um内控制其流失的关键营力在细沟间和细沟阶段分别为雨滴打击和交互作用；90 mm/h雨强下，控制微团聚体各粒径流失的主导因素在细沟间和细沟阶段分别为径流和雨滴打击作用。