东北黑土区农田春季融雪细沟侵蚀机制与过程

Rill evolution accelerates snowmelt erosion in black soil farmland during snow-melting period, in the Northeast of China, which has seriously endangered the security of the black soil depth and land productivity. Snowmelt-induced rill erosion, comparing with rainfall-induced rill erosion, has its unique characteristics, including snowmelt runoff as erosion force, the unthawed layer of surface soil, and the freezing and thaw (FT) action of surrounding environment. However, little information has been focused on the mechanism and process of this kind of rill erosion. Laboratory simulation tests will be adopted to investigate the effect of snow characteristics, slope gradients, the amount of energy on the snowmelt runoff, combined with observation of snowmelt runoff in runoff plots, based on which an improved runoff curve method was given and validated to simulate the snowmelt runoff on farmland in the black soil region of northeast China. And the effect of runoff amounts, slope gradients, FT temperature differences and soil initial water contents on rill collapsing formation, combined with the collapsing regular patterns under different energy, would be used to study the mechanism of snowmelt-induced rill collapsing under FT surrounding environment. Simulation test of intermittent snowmelt rill erosion will be adopted to investigate the influence of runoff amounts, slope gradients, FT setting and soil initial water contents on the rill erosion process, in order to investigate the relative contribution and mutual feed effect of snowmelt runoff, FT action and collapsing in the rill erosion process. Mechanism and process of snowmelt-induced rill erosion are expounded on the basis of these result above. The study would provide certain basis for forecast and prevention of snowmelt-induced rill erosion in the black soil area of Northeast China, and also further supplement and enrich the relative theoretical research.

细沟发育加剧了东北黑土区农田融雪侵蚀，严重危及土层厚度与土地生产力。融雪细沟侵蚀区别于降雨细沟侵蚀的显著差异包括融雪径流作为侵蚀营力、表土不完全解冻层及其所受昼融夜冻的环境影响，其机制与过程有待深入研究。项目通过模拟不同积雪特征、坡度、外界能量对融雪产流的影响，结合径流小区融雪产流观测，提出并验证适合模拟东北黑土农田坡面融雪产流的改进径流曲线法；通过模拟不同坡度、径流量、冻融温差、土壤初始含水率条件下形成细沟坍塌体，以及不同外界能量下的沟壁坍塌规律，揭示昼融夜冻影响下的融雪侵蚀细沟坍塌机制；利用间歇性融雪细沟侵蚀模拟试验，研究不同坡度、径流量、土壤初始含水率、冻融情况对融雪细沟侵蚀影响，分析融雪径流、冻融作用、重力坍塌等因素在融雪细沟侵蚀过程中的相对贡献与互馈作用。综合上述研究结果，阐述融雪细沟侵蚀机制与过程，以期为预防东北黑土区寒季水土流失提供参考，并补充、丰富融雪细沟侵蚀的相关研究。

东北黑土农田春季融雪细沟侵蚀的显著特征包括融雪径流、冻融作用与细沟坍塌等。针对东北季节性积雪区融雪特点，通过融雪产流模拟试验，分析了在不同积雪密度和雪水当量的条件下积雪初始产流时间、产流后期时间、积雪融化总时间、融雪水量及其变化、融雪速率及融雪径流、产流前后积雪持水能力等产流特征的特点与规律。针对融雪细沟侵蚀较为独特的沟壁坍塌现象，根据融雪侵蚀过程中的细沟坍塌试验，观测冻融温差、土壤初始含水量、坡度及径流量对坍塌体干密度、坍塌体孔隙度、坍塌体坍塌时间、坍塌体含水量等指标的影响。根据融雪侵蚀后的细沟坍塌试验，分析冻融温差、土壤初始含水量、坍塌体坡度对坍塌体坍塌时间等坍塌特征的影响。通过融雪细沟侵蚀模拟试验，针对不同解冻状态与典型措施等背景，对融雪径流流速、融雪径流含沙量、融雪细沟侵蚀特征进行了观测，对相关水动力参数、融雪细沟发育过程以及主要侵蚀营力进行了分析。研究结果可为融雪细沟侵蚀机制与预防提供一定参考。