长江上游干暖河谷冲沟景观的发生演变

Past Gully Development in the Warm-Dry Valley of Xichang, SW-China

通过对小流域的航片、土壤剖面、泥沙堆积与土地利用历史等详尽的综合对比分析 ,定量评价了土地利用变化对冲沟发生演变的影响。在长江上游安宁河干暖河谷选择了两个代表性的冲沟 ,分别对其形状和土壤流失的体积进行了详细的野外调查、测定和计算。研究结果表明 ,西昌安宁河干暖河谷的冲沟侵蚀速率高达 375吨 /公顷 /年。西昌地区数百年来景观持续演变 ,特别是 2 0世纪中期人为强烈的不合理采伐森林、过度放牧和农业垦殖 ,造成了大量冲沟系统的形成和发展。采取以控制冲沟侵蚀为主的有效水土保持措施 。

Gully erosion due to overland flow is the most important issue for environment protection in Southwest China. The objective of this study is to investigate the development of past gully systems and their long-term relation to land use changes. The first investigations were carried out at the slopes bordering of the Anning Warm-Dry Valley of southern Sichuan in the territory of Xichang. Two gully systems were investigated in details. The size (length, average depth and width) and the volume of the gully system were measured in the field and calculated. The size of the surface catchment of the gully system was measured in the field, too. Air photos were analyzed, senior experts and farmers were interviewed for a detailed reconstruction of land use history. After several centuries of sustainable landscape development namely the intensive agricultural land use during the second half of the 20th century caused excessive floods and gullying in wide parts of southern Sichuan. Valley bottoms were flooded, rivers changed their position, many villages ceased there and lakes were filled with sediments. Gullying rates that could be reconstructed are unexpectedly high and strongly demand sudden successful measures of soil and water conservation.