汶川地震对典型亚热带森林地表径流和土壤侵蚀的影响

Runoff and Soil Loss of a Typical Subtropical Forest Stricken by Wenchuan Earthquake

汶川大地震使龙门山区的山地生态系统遭受了极大的破坏.通过四川盆地西缘龙门山区典型亚热带森林两种样地(滑坡体和森林)的对比,采用布设微型径流仪的方式,分别对降水、植被盖度、坡度与径流及土壤侵蚀的关系进行了定量研究;进而采取分级比较的方式,对不同强度的土壤侵蚀进行了分析.结果显示:1)滑坡体比森林样地产生更多的累积径流量和累积侵蚀量,且两者间存在着显著性差异;2)滑坡体样地上,地表径流量及土壤侵蚀量与坡度呈显著正相关(P<0.01),而森林样地的地表径流量及土壤侵蚀量与坡度也有正相关关系,但是并不显著;3)单位面积内滑坡体比森林对照样地产生更多的地表径流和土壤侵蚀,且地表径流与土壤侵蚀量均呈显著正相关,滑坡体样地单位地表径流量的增加导致更严重的土壤侵蚀;4)土壤侵蚀分级比较表明,滑坡体"强烈"以上等级的土壤侵蚀量所占比例居多,而森林对照样地上超过80%土壤侵蚀属于"轻度".即使在"轻度"等级中,滑坡体产生的土壤侵蚀量(202.35 t/km2)比森林样地(0.52 t/km2)也高出400倍以上.

After the catastrophic Wenchuan earthquake in 2008, mountainous ecosystems in the Longmen Mountains were seriously destructed. This study aimed to investigate the relationships among rainfall, slope gradients, vegetation cover, and runoff as well as soil loss, through comparing forests and earthquake-induced landslides. Micro-catchments were established on north-facing slopes with PVC material plots （50 cm ？50 cm） from August to September 2010. The grading comparison method was adopted to compare soil erosion of different intensities. The result demonstrated significant difference between the amount of accumulate？d runoff of landslide sites and forests sites. There was less runoff and soil loss at forests sites than landslide sites due to complicated community structures and rainfall interception of forests. There was more serious soil erosion at landslides sites with runoff increase per unit. Classification and gradation of soil erosion intensity indicated that the proportion of total soil loss exceeding S （severe） grade was the highest at landslides sites, while more than 80% soil erosion belonged to VL （very low） at forests sites. Even at VL grade, landslide sites produced 202.35 ton per km2, nearly 400 times more than that at forest sites of 0.52 ton per km2. There was more than 4.72 ？106 t soil loss produced from earthquake-induced landslides even two years lat？er. It is now still a great challenge for ecological restoration and rehabilitation of earthquake damaged areas due to the spatial and temporal difference of heavy rainfall, which always leads to serious landslides on a large scale. Fig 6, Tab 3, Ref 37