Study On The Pattern Change Of Land Use/land Cover And Soil Erosion Of Bishan County In Chongqing

Soil erosion in Three Gorges Reservoir Region and its neighbour area has been a great threat. According to the theory of landscape ecology, the spatial patterns of land-use/land cover and soil erosion in Bishan County were studied from 1995 to 2000, using Remote Sensing(RS) and Geographical Information System(GIS). The data of land use/land cover and soil erosion was interpreted from Landsat TM Images, and the degree of land use index, the rate of change of land use/land cover, the soil erosion index and some landscape metrics were used to analysis the spatial patterns and dynamics of land-use/land cover and soil erosion in the study area.The results show that the degree of land use was high, the plowland and forest were the main types of land use/land cover in Bishan. The shape of plowland was the most complicated in all types. Other land use types has transformed to dry land with a high percent during 5 years. The forest distributed in the East and West Mountains. The forest patches were even. The Contagion Index of forest was high, but that in 2000 was less than in 1995. The area of Construction land increased and the rate was highest during 5 years, mainly due to the increase of residential area. The area which transformed to grassland from forest was small, but the rate was high.The results on spatial pattern of soil erosion showed that the change range of severe erosion and middle erosion was great. In 5 years, 49.76% severe erosion has transformed to middle erosion, 0.64% to slight erosion and 0.26% to tiny erosion. The total area of middle erosion increased obviously, but the degree of erosion in the whole county did not worsen. Form the whole landscape pattern, the Number of patches, the Shannon's Diversity Index and Richness decreased and the Contagion Index, the largest patch index and Shannon's Evenness Index increased, which showed that the landscape pattern of soil erosion was more compact and several types became dominant.Land use/land cover had effect on the degree of soil erosion. Plowland and immature forest were the main types resulted in soil erosion, where soil erosion was in middle and slight degree. 0.09 hm~2 forests degenerated to grassland, where soil erosion changed from middle to severe degree. In grassland type, the area of soil erosion increased while the degree of erosion decreased. The natural water was not destroyed, where the area of erosion decreased in 5 years.In brief, the heterogeneity of land-use/land cover pattern increased gradually and the pattern of land use became diverse and even in Bishan. The development of land use was rational according to the natural rules and had not destroyed the landscape ecological function. The rational land use was important for regional sustainable development.