紫色丘陵区不同侵蚀沉积地段土壤结构特征

以中国科学院盐亭紫色土农业生态试验站小流域为例，研究不同土壤侵蚀沉积地段（斜坡和沟谷不同部位）的土壤结构特征，以了解侵蚀沉积对土壤结构的影响。结果表明，在植被覆盖较好的坡体顶部，土壤侵蚀较弱，团聚度达到30．1％，MWD变化为3．4mm，土壤结构良好；沟谷底部由于沉积而有较多细土物质并具有适宜的水分条件，有利于土壤团聚体的形成，结构状况亦较好，团聚度达到50．3％，结构保持率为35．4％；而坡腰侵蚀较严重，团聚度仅为13．6％，结构保持率为14．1％，土壤结构状况较差。

Soil Structure Characteristics of Different Erosion-sediment Sites in the Hilly Area of Purple Soils

A case study was conducted in a typical small watershed of Yanting Agri-ecological Station of Purple Soil, Chinese Academy of Sciences. The effects of erosion-sediment on soil structure were analyzed in this paper using the soil structure indexes calculated from analyzed results of particle components of soil samples obtained from different sites at hill topand bottom of watershed. Results showed that, the structure of soil on hill top is in good conditions due to artificial forest. Water stable aggregate content was up to 30.1% and the change of mean weight diameter was 3.4 mm ; That of the buttom site of watershed is also fine because of large amount of clay incluced by sedimentation, which accelerated aggregates forming. Water stable aggregate content was up to 50.3% and persent of construction preserve was 35.4% ; and those on other positions are all in poor conditions because of severe soil erosion.