2001-2010年洞庭湖生态系统质量遥感综合评价与变化分析

生态系统质量能够反映生态系统的重要特征,是表征生态环境质量和服务功能的重要指标。在生态系统质量的理论框架指导下,结合GIS综合指数法,利用遥感数据和土地覆被数据,对2001—2010年洞庭湖区域各生态系统类型进行生态系统质量综合评价和变化分析。以NPP年均值和变异系数构建生态系统生产能力指数(EPI)和稳定性指数(ESI),结合PSR模型和AHP层次分析法构建生态系统承载力指数(EBCI),并基于熵值权重法,构建生态系统质量遥感综合评价模型,实现对生态系统生产能力、稳定性和承载力三方面的综合评价。结果表明,洞庭湖区域生态系统质量综合评价分数达到59.81(总分100),而且在三项指数评价中,各指数均值分别为72.79、52.21和71.86,可见洞庭湖区域生态系统稳定性略差。三项指数在2001—2010年期间变化表现不同,EPI和EBCI分别下降8.85%和9.11%,ESI小幅度上升3.09%;整体生态系统质量在2001—2010年呈现逐年降低趋势,下降5.97%,平均变化率为-0.508/年。针对各生态系统类型的分析可知,森林生态系统质量高于其他生态系统类型,湿地生态系统质量最低,同时在这十年间,湿地生态系统质量下降最明显,降幅达12.97%,森林生态系统质量变化较小,降幅只有2.26%。

Ecosystem quality comprehensive evaluation and change analysis of Dongting Lake in 2001-2010 based on remote sensing

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.