三峡库区小流域不同生态恢复阶段的水土流失特征

Effects of Soil and Water Losses During Different Ecological Restoration Stages of Small Watersheds in Three Gorges Reservoir Area

在三峡库区汝溪河小流域,采用"空间代替时间"方法对撂荒地和柏木新造林、幼龄林、中龄林4个恢复阶段的水土流失特征进行研究。结果表明:撂荒地演变为柏木新造林、幼龄林和中龄林后,水土流失明显减少,土壤流失量大小排序为撂荒地>新造林>幼龄林>中龄林;表层(0-20cm)土壤砂粒含量分别减少2.95%,6.86%和9.51%,而粗粉粒和物理性粘粒含量增加;各层土壤的抗蚀性明显增强,且随土层加深而降低;各层土壤团聚体的稳定性提高,而且土壤团聚体破坏率均需较长时间达到稳定,尤其是幼龄林和中龄林。可见,植被的保持水土、改良土壤作用随生态恢复进程得到增强。但在三峡库区增加森林植被覆盖的同时,还应注重培育和维护合理的林分结构。

By the method of taking space instead of time,characteristics of soil and water losses of four ecological restoration stages(abandoned land,new forestation,sapling forest and mid-maturation forest for Cupressus funebris)were studied in Ruxi watershed of Three Gorges Reservoir area.Results showed that,soil and water losses decreased remarkably after abandoned land changed into new forestation and sapling forest and mid-maturation forest.The order of soil losses amount was abandoned land>new forestation> sapling forest>mid-maturation forest.Sand contents in surface soil layer(0-20cm)decreased by 2.95%,6.86% and 9.51% respectively,but coarse silt and physical clay contents increased.Soil anti-erodibility strengthened obviously in all soil layers and declined with increasing soil depth.Stability of soil aggregate in all soil layers was also improved,and it took the rate of soil aggregate deterioration longer time to reach a stable level,especially sapling forest and mid-maturation forest.Therefore,vegetation functions about soil and water conservation and soil improvement were strengthened with the processes of ecological restoration,but it should be also paid more attention to cultivate and maintain reasonable structure of forest stand when increased forest coverage in Three Gorges Reservoir area.