Spatial Variation and Dynamics of Ecosystem Health in the Taihu Lake Watershed
太湖流域生态系统健康的空间分异及其动态转移

Based on ecological characteristics of the Taihu Lake watershed, the authors synthetically considered mechanisms of the interactions among ecosystems in the watershed. Using multiple scenes of Landsat Thematic Mapper (TM) imageries, land use/cover data, field investigation data, and social statistic data within the framework of the Pressure-State-Response (P-S-R) model, we constructed a comprehensive assessment index system about ecosystem health, evaluated the ecological health of the Taihu Lake watershed, as well as analyzed the spatial variation and dynamics of ecosystem health. Results showed that during the period 2000-2008, the ecosystem health maintained a subhealthy level as a whole. The comprehensive ecological health index decreased from 0.584 to 0.512, with showing a decreasing comprehensive ecological health index across almost 92% of the study area. Areas with better, moderate, and worse health conditions accounted for 14.29%, 71.43%, and 14.29% of the total area, respectively. There were no areas with the best health conditions. Ecological health for about 28.57% of the area changed from a better condition to a moderate or a worse one. This might be related to increases in external pressures as well as the degradation of the resilience and structure of the ecosystem. The spatial distribution of ecological health exhibited obviously regional differences, with suggesting that the comprehensive ecological health index decreased from the northeast to the southwest. Southwestern regions, containing Anji County, Deqing County, and Changxing County, all showed better ecological health conditions. Human activities and population pressures over these regions showed less influence on the ecological health status and a strong primary productivity. This implied a reasonable structure of the ecosystem. The resilience was generally higher than other regions. Ecosystems showed a multitude of functions such as water conservation and purification. Northeastern areas generally showed a worse ecological health condition, including Wuxi and Changzhou Cities. Ecosystems across these regions were being faced with great pressures resulting from human activities.