三峡库区水源涵养重要区生态系统格局动态演变特征

利用三期遥感分类数据为基础数据源,结合野外地面核查和生态空间分析方法,对三峡库区水源涵养重要区2000~2010年生态系统格局时空动态变化进行了分析。结果表明:研究区内各类生态系统空间分布差异较大,以森林和农田为主体生态系统;10a间,由于三峡水库蓄水淹没了大量农田和林地,导致森林生态系统和农田生态系统分别向湿地生态系统转化了179.99km2和191.27km2;其他生态系统(主要是人工表面)面积在时段内增加了506.63km2,主要是城镇建设占用部分森林和农田转换而来;时段内森林生态系统总的面积未发生较大减少主要是由于近年退耕还林、森林工程等生态工程的实施获得了大量补充;研究区后期的生态系统转化强度在逐渐增强,生态系统动态类型相互转化强度也显示出研究区生态系统类型的转化总体变差。

SPATIAL-TEMPORAL CHANGES OF ECOSYSTEM PATTERN IN THE THREE GORGES RESERVOIR WATER CONSERVATION AREA

The water conservation area in the Three Gorges Reservoir plays a key role in water and soil conservation, biodiversity protection, and even in the health of Yangtze River and ecological safety of the state. With the rapid development of urbanization, industrialization and a huge increase in water resources and energy consumption in this area, the structure and function of the original ecosystems, to some extent, have been destroyed in recent years, resulting in a series of ecological and environment problems. All of these changes have attracted great attention from ecologists, environmentalists and geologists over the past decade, but the most of studies focused on the geological disasters, water and soil loss and the environmental problems of drawdown area. The knowledge to elaborate the precise impact that the impoundment of the Three Gorges has effect on the structure and function of the ecosystems is extremely sparse. The goal is to provide us with theoretical support for water resource management and collaborative development of nature and society. This paper, using remote sensing classification data of three periods (in Aug. 2000, Aug. 2005 and Aug. 2010) as data sources, combined with field verification and ecological spatial methods to analysis the spatial temporal changes of ecosystem pattern in the Three Gorges Reservoir Water Conservation Area during 2000-2010. To establish the evaluation index systems of ecosystem pattern change in the study area, we used the method of ecological space analysis that is to solve the problem from the perspective of ecological system structure, the characteristics of the landscape pattern and the transformations of ecosystem. Results showed as follows. The spatial distribution of various ecosystems is different obviously. Forest and farmland ecosystems are the main types located in this region. Forest ecosystems are mainly distributed in the higher altitudes and high mountains areas of east and Midwest of Three Gorges Reservoir, while farmland ecosystems are mainly distributed in the west flat areas. The Three Gorges Reservoir flooded a lot of farmland and woodland, and eventually led transformation of forest and agricultural lands to wetlands, with 179.99 km2 and 191.27 km2 respectively. These new born wetlands are mainly distributed in the main stream and tributaries areas of the Yangtze river. The main reason for these changes is that the areas below 175 m elevations on both sides of the Yangtze River were directly converted to wetland after the impoundment of the Three Gorges Reservoir. Urban construction occupied part of farmland and woodland，then causing other ecosystem (mainly is the artificial surface) areas increased 506.63 km2. Total area of the forest ecosystems didn’t decrease sharply due to the project of returning grain plots to forestry and others related ecological projects. Comprehensive ecosystem dynamic in the Three Gorges Reservoir water conservation area was 1.40% during 2005-2010, but this data had been increased to 2.39% during 2005-2010, which means that the strength of ecosystem conversion was gradually enhanced. Conversion intensity of dynamic ecosystem types in this area was 188% from 2000 to 2005, but this data had been sharply declined to 0.44% during next five years. That is to say, the overall ecosystem conversion has deteriorated in the later period.