Change of land use/land cover and landscape pattern in the backwater variation area of the Sanmenxia reservoir

The variation of water level in the Sanmenxia reservoir has considerable influence on the local eco-environment, land use and streamflow regime. With the combination of remote sensing(RS) and geographic information system(GIS) techniques, the variation of land use/land cover at downstream of Tongguan in the Sanmenxia reservoir in both flood and non-flood seasons in typical years during 1987～2002 were analyzed. On the basis of landscape ecology theory, variation of landscape pattern with the change of water level was analyzed. Results show that area of both river and farmland decreases in both flood and non-flood seasons, but the area of bare land increases. The forest land area shows little variation in both flood and non-flood seasons. All the eco-system area in seasonal inundation area decreases except the area of gravel bottomland, which is significantly influenced by the variation of water level. Farmland area in terrace land decreases, but the area of both grassland and bare land increases considerably, which shows the ascending trend in the height of grassland distribution. The results of landscape pattern analysis show that landscape diversity and landscape equality exhibits declining trend and the ecosystem may become more singleness and heterogeneous. Landscape fragmentation shows increasing trend, relative dominance slightly increases, control strength shows increasing tread by ecosystems in terrace land.