农田土壤风蚀可蚀性动态变化机理研究

Understanding and further quantifying soil wind erodibility is critical for soil degradation assessing and wind erosion modeling. Yet few studies related temporal change with different scale (during a single wind erosion event, monthly, seasonal and annual scales) of soil wind erodibility and its impacts on wind erosion are performed to date in the arid and semi-arid northern China. In this study, a method combined wind tunnel with field-laboratory experiments would be applied to estimate temporal change for soil wind erodibility in Bashang Region, Hebei. By these means, the temporal change of soil wind erodibility for popular agricultural land management practices would be quantified using field-laboratory wind erosion observing system. In light of these data, some aspects for soil intrinsic properties, land management practices and climate would be tested and summarized as the factors affecting temporal change of soil wind erodibility. Furthermore, the temporal change pattern and mechanism of soil wind erodibility would be ascertained, the relationship between soil wind erodibility and wind erosion rate would be investigated, and a scheme would be developed and validated for modelling the temporal change of soil wind erodibility of farmland at a field scale in Bashang Region, Hebei. The study would help researchers comprehend the mechanism of the temporal change of soil wind erodibility, and further apply the scheme to traditional models (such as RWEQ, WEPS etc.) or facilitating to develop a dynamic model for evaluating wind erosion.

土壤风蚀可蚀性是指土壤遭受风蚀的脆弱性程度，它既是土壤风蚀机理研究的重要内容，也是土壤风蚀预报模型的必需参数之一。目前对土壤风蚀可蚀性动态变化及其对风蚀的影响研究依然不足。本研究拟在河北坝上典型农田区，采用野外观测采样、风洞实验、室内实验以及模型模拟相结合的手段，对不同时间尺度下（风蚀事件—月—季节—年际）农田土壤风蚀可蚀性指标动态变化机理进行系统研究，确定土壤内在属性（土壤质地、土壤有机质和碳酸钙含量等）和外在影响因素（农田管理措施、气象气候因素等）对土壤风蚀可蚀性指标动态变化的影响，阐明土壤风蚀可蚀性指标动态变化的关键影响因子及其机理，分析风蚀可蚀性动态变化对风蚀速率的影响，构建并评估土壤风蚀可蚀性指标动态变化预测模型。本项研究有助于提升土壤风蚀可蚀性的理论认识和实际应用水平，为我国土壤风蚀模型研制提供重要参数，推动风蚀模型研究进步。

研究期间项目组围绕土壤风蚀可蚀性指标动态变化特征、机理及其对风蚀速率的影响等方面，主要以河北坝上农田表层土壤为研究对象，通过野外调查观测、风洞试验、室内实验以及数据分析等方法取得了以下主要进展：（1）大风蚀事件过程中，风蚀前期表层土壤可蚀性迅速变小，进而土壤风蚀速率随之显著降低。风蚀中后期，粗化地表导致可风蚀物减少，风蚀速率趋于稳定。土壤质地、有机质和砾石含量与土壤可蚀性指标（干团聚体粒径分布等）显著相关，是影响风蚀过程中地表粗化进程的重要因素；（2）根据土壤风蚀可蚀性变化特征，可将其划分为4个阶段：秋季风蚀阶段、冬季风蚀阶段、冻融交替风蚀阶段及春季风蚀阶段。其中春季可蚀性最大，冬春过渡期的冻融交替节段可蚀性最小；（3）对比分析春季农田、林地、草地表土的潜在风蚀可蚀性，其中草地可蚀性最大、农田最小，表明草地和林地地表如受到破坏风蚀潜力很大；（4）土壤微塑料丰度随干团聚体粒径的增大以指数函数减少，可能是影响覆膜农田土壤风蚀可蚀性的重要因素。