东北黑土区土壤团聚体迁移特征的模拟降雨试验研究

坡面侵蚀过程中土壤团聚体迁移反映了团聚体的破碎程度以及雨滴打击和径流搬运之间的相互作用。基于模拟降雨试验,研究了黑土坡面不同粒级土壤团聚体的迁移特征。研究结果表明,同干筛处理相比,湿筛后≥0.25mm粒径的水稳性团聚体含量为52%,其较干筛处理减少24%。湿筛后土壤团聚体的粒级分布以<0.25mm团聚体居多;湿筛处理后>1mm粒级的团聚体含量较干筛处理减少了83.8%。在50和100mm/h两个降雨强度下,团聚体流失以<0.25mm的微团聚体为主,其流失量占团聚体流失总量的80%以上,且不同降雨强度下微团聚体流失量与含沙浓度存在显著正相关关系。50mm/h降雨强度下微团聚体流失量随降雨历时的增加呈先快速增加后递减,最后趋于相对稳定的变化趋势;而100mm/h降雨强度下,其变化趋势则表现为先快速增加后缓慢上升趋势。≥0.25mm各粒级团聚体的流失比例和流失团聚体的平均重量直径(MWD)均随降雨强度的增加而减小,反映了大雨强下雨滴打击对团聚体的分散作用。

Soil Aggregate Movement in Black Soil Region of Northeast China

The aggregate movement during hillslope erosion process reflects the interaction among the aggregate breakage,raindrop impact and runoff transportation.The simulated rainfall experiment was designed to quantify movement characteristics of variously sized aggregates on hillslope farmlands of the black soil region,Northeast China.The results showed that the content of 0.25 mm water-stable soil aggregate was about 52%,24% lower than the contents obtained through dry sieving,while 1 mm soil aggregates contents was 83.8% lower.The majority of the water-stable soil aggregates was 0.25 mm aggregates.Under rainfalls of 50 and 100 mm/h intensities,0.25 mm aggregates contributed most of the aggregate loss,accounting for more than 80% of the total aggregate loss.The micro-aggregate loss rates were found significantly positively correlated with sediment concentrations under both rainfall intensities.As the rainfall time extended,the loss rate of micro-aggregate rapidly increased from the initial stage and then decreased in a short period of time and reached a relatively stable stage under 50 mm/h rainfall intensity;while under 100 mm/h rainfall intensity,the micro-aggregate loss rate increased quickly and increased slowly after the peak value was reached.The proportion of 0.25 mm aggregates loss and MWD of aggregates losses decreased with the increase of rainfall intensity,indicating that raindrop impact had played a great role in separating aggregates.