Ecosystem quality, which reflects important ecosystem characteristics, is an important indicator in characterizing the quality and service functions of the ecological environment. In this paper, we have been guided by the ecosystem quality theoretical framework, based on the GIS integrated index method, in using remotely sensed data and land cover data to conduct a comprehensive evaluation and change analysis of ecosystem quality for various ecosystem types in the Dongting Lake area from 2001 to 2010. We have proposed an ecosystem productivity index (EPI), an ecosystem stability index (ESI), and an ecosystem bearing capacity index (EBCI) to build a remotely sensed ecosystem quality comprehensive evaluation model. We used this model to evaluate three aspects of ecosystem quality: ecosystem production capacity, stability, and carrying capacity. This model enabled us to obtain EPI and ESI by linear stretching of the annual average value of net primary productivity (NPP) and the variation coefficient of NPP, respectively. We built the EBCI using an ecosystem health index based on the pressure-status-reflection (PSR) model and analytic hierarchy process (AHP), combining these indices by the entropy weight method. Using the remotely sensed ecosystem quality comprehensive evaluation model, we calculated the EPI, ESI, EBCI, and ecosystem quality index of five ecosystem types, forest, grassland, wetlands, farmland and urban areas, around Dongting Lake. We evaluated the quality of these five types of ecosystem by grading these index values. We also analyzed the change trends of these indices by calculating the average change rate of the EPI, ESI, EBCI, and ecosystem quality index from 2001 to 2010 in these five areas.
The results indicated that the mean value of the ecosystem quality comprehensive evaluation index of the five ecosystems in the Dongting Lake area was 59.81 (total score: 100). After evaluating the ecosystem production capacity, stability, and carrying capacity indices, we found that the indices produced values of 72.79, 52.21, and 71.86, respectively, indicating that ecosystem stability in the Dongting Lake area was poor in the period from 2001 to 2010. However, the three indices showed different change trends during the period. Two indices, EPI and EBCI, decreased by 8.85% and 9.11%, respectively, but ESI rose slightly, by 3.09%. The ecosystem quality declined by 5.97% from 2001 to 2010, the average change rate being -0.508 per year. An analysis of the various ecosystem types found that the forest ecosystem's quality was better than the other ecosystem types, and that the wetlands ecosystem quality was the lowest. We found that, from 2001 to 2010, the ecosystem quality of the wetlands had the most obvious decline (12.97%) and that the forest ecosystem only decreased by 2.26%. These data indicate that ecosystem quality in the Dongting Lake area fell from 2001 to 2010, with the wetlands ecosystem having the largest decline. At present, the ecosystem quality remains at a higher level than that indicated by these historical data, but it seem unlikely to lead to optimistic trends in the future. We should pay more attention to environmental protection and ecological planning in the Dongting Lake area.