川江流域生态地貌系统稳定性影响因素

INFLUENCING FACTORS ON STABILITY OF GEOMORPHOLOGY-ECOSYSTEM IN THE CHUANJIANG BASIN

川江流域片蚀与地表物质组成、坡度和坡长关系密切,且明显受地貌类型控制;沟蚀与森林覆盖率呈负相关,而和人口密度呈正相关;重力侵蚀在盆周山区和流域西北部高山中山区危害严重;人类消极活动在盆中丘陵区因人口稠密而活跃。这四个因素的发生发展制约着本流域生态地貌系统的稳定性。

The Chuanjiang Basin includes the Jialingjiang and Tuojiang Basins and the upper reaches of the Minjiang River, which are seperately 3 tributaries on the upper reaches of the Changjiang River in Sichuan Province. The total area of Chuanjiang Basin is 16×104km2. In the region,the stability of geomorphology-ecosystem is very weak. It is mainly caused by following factors.1. Sheet Erosion; It is one of the most important influencing factors on the stability of geomorphology-ecosystem,and it is very widely and seriously. According to the field measured data,sheet erosion volume is the power function of gradient,positive related with slope length and obviously controlled by lithologic fabricates and landform types.2.Ravine Erosion-Its capability is represented by the average ravine density of each county derived from the average ravine density of I -grade watershed on 1:50,000 topographic maps based on Haudon Law. In the region, ravine density is negative and positive related seperately with the average forest cover ratio and population density of each county. Above result shows that ravine erosion is another influence factor on the stability of geomorphology-ecosystem in the Basin.3.Gravity Erosion :Collapse,landslide and debris flow with high frequency and great scale have serious affections on the stability of geomorphology-ecosystem at the middle and upper reaches of the Chuanjiang Basin. They are usually accompanied with special lithology .sharp slope and irrational lumbering.4.Human Activities;Its positive and negative affections on the stability of geomorphology-ecosystem are easily resulted from the wave change of forest cover ratio in past decades. Although negative human activities trend to diminish in recent years, slope fields, especially steep slope fields are still eroded violently.