Abstract: Supporting by land use geodatabase, and using regional ecological quality index and land use change ecological contribution index, a quantitative study was made on the ecological effects of land use in Poyang Lake region. The results indicated that in this region, the average regional ecological quality index was 7.60 in 1990 and 7.62 in 2002, and the overall ecological quality lay between those of shrubbery and sparse woods. From 1990 to 2002, the main driving forces leading to the improvement of regional ecological quality index were the expansion of pond and reservoir, forest, and sparse woods, while the main reasons for the degradation of regional ecological quality index were the shrinkage of paddy field and middle coverage grassland. As for the land use change ecological contribution index, the sum of the ecological contribution rates in the changes from paddy field to forest, upland to forest, paddy field to sparse woods, and paddy field to pond and reservoir was up to 52.96% of the total, which constituted the main land use change for the improvement of ecological environment, while the sum of the ecological contribution rates in the changes from forest to paddy field, forest to upland, and paddy field to rural residential area accounted for 39.89% of the total, which constituted the main land use change for the degradation of ecological environment.

Key words: Converting farmland to forestland, Composite ecosystem, Fine root, Grass root, Nutrient, Decomposition