The Ecological Health Based On The Theory Of Landscape Ecology Of The Three Rivers Wetlands

Three Rivers Wetland is the cradle of Yangtze River、Yellow River and Lancang River, which provide water for the production and our usual life, and play a pirotal role in the worldwide ecosystem operation. In recent years, a large number of the ecological problems occurred in source area, such as the destruction of vegetation and soil erosion, causing widespread concern. Taking the source area as the subject, based on the remote sensing images in 1990 and 2013, extracted the NDVI, maked classfication, and calculated the landscape pattern indices in ENVI, ArcGIS and Fragstats, and analyzed the landscape pattern changes and influences. Finally, Based on the landscape pattern indices, we constructed an evaluation system consisting of vigor, organization, resilience and services to do the ecological health assessment, and provided the scientific evidence for the related department to do some reasonable ecological plannings.Compared different classification method of remote sensing image, in connection with the characteristics and formulas of NDVI, to build decision trees to complete the wetland system division. Ultimately, we got five types including lakes, rivers, swamps, vegetation and water. Proven, the result was consistent with the official data, and the error was less than 15%.Calculated the landscape indices of source area in 1990 and 2013, and analyzed the data from classes level, patches level and landscape level. From class level, lakes in the source area had an area of approximately 80% and the area increased by 2.5%, dominated the source area. The area of rivers increased by 1.3%, while the area of swamps and vegetation reduced by 43% and 72%. The aggregation index of the five features were greater than 70, indicating the higher polymerization degree in source area; From patch level, based on the leading position of lakes, selecting the typical lakes to do the analysis, showed that the lakes had a healthy growth and the area of eling increased 7.43% and the circumference increased 76.3%, whose healthy growth were most significant. From landscape level, the increase of the area of landscape meaned the increase of drainage area and water. The largest patch index remained stable, meaning that the dominant patches were evident. Others were fluctuate within a narrow range, like patch density and contagion index, whose changes meaned that the landscape fragmentation increased. Shannon diversity index and evenness index increased, indicating that the landscape was moving towards a balanced development in terms of plaque composition.The ecological health assessment were conducted from spatial and temporal scales. In spatial scales, based on data in 2013, in Yellow River source, the ecological health of zalingeling partition was in sub-health state (4.02), and the ecological health of donggeicuona partition was in health state (6.91), and the ecological health of dongzhong partition in Yangtze River source was in health state (6.57), while the ecological health value of dangqu partition and guozongmucha partition in Lancang River source were were both in sub-health state (4.25 and 4.33). In temporal scales, took the zalingeling partition as example, showing that the ecological health of lakes were in highly health (8.47) and health (7.99) state in 1990 and 2013, that the ecological health of rivers were in sub-health(4.17 and 4.18) state in 1990 and 2013, that the ecological health of swamps were in sub-health(4.34) state in 1990 and 2013, that the ecological health of vegetation were in sub-health (5.98 and 4.96) state in 1990 and 2013, that the ecological health of water were in sub-health (4.17 and 4.11) state in 1990 and 2013.In summary, the value of the ecological health of the Lancang River was lower than Yellow River and Yangtze River. And the value of lakes, rivers, swamps and water were in the sub-health state. In short, the source area was in the sub-health state. The departments need to continue to carry out a large number of afforestation activities, to improve the vitality. Simultaneously, the intensity and time of the livestock stocking needs to be controled, to restore the productivity of grasses. As for the problem of the increase of the area of lakes and rivers, we need to take timely measures to avoid the flood disasters.