| Based on the GIS platform, the forest ecosystem health evaluation in Three-Gorge reservoir area was taken as the main research objective in this dissertation. By taking full use of the historical data of national forest resources investigation and the located monitoring network system, expanded the monitor content, the quantified evaluation on the structure, function, stability and landscape security pattern of forest resources in Three-Gorge reservoir area were given at forest level, landscape level and regional level respectively, and this breakthrough the limitation to take single population or community as the center in the former ecological study.Firstly, based on the investigation data from the typical sample plots and combined with the subcompartment data from the second level forest resources census, the evaluation model and the species biodiversity quantified indicator system which based on the species richness index, species biodiversity index and evenness index in Three-Gorge reservoir area was established at regional level. This directly reflected the species richness, changing degree and evenness in the Three-Gorge reservoir area at large scale, disclosed the basic difference on the components and structure of forest ecosystem, objectively reflect the real status of the communities, and it is a method with the scientific, operational and flexible characteristics. And the quantified analysis and the integrated evaluation on the structure biodiversity of forest ecosystem were given in the typical regions both at species and landscape level. The quantified description on the biodiversity in Three-Gorge reservoir area was not only the basis for the evaluation on current status, but also the basis which affect the forecast, furthermore, it is the existing issue which eagerly need to be addressed in the plan and decision process during which the managers take the biodiversity into account, thereby, this research provided an quantified basis for the management of forest ecosystem health.Secondly, based on the evaluation on the productivity/biomass in the Three-Gorge reservoir area, the current status of the basic produce function in the Three-Gorge reservoir area is 6,847,000 ton, distribute unevenly, and the Wuxi county with the highest ecosystem biomass which account 12% of the total biomass in the Three-Gorge reservoir area, the Xingshan and Yiling County are is next. Generally speaking, the more biomass of the forest ecosystem, the more indirect values it has, the northeast and southern part in the research area were with higher biomass, it is these biomass which support the ecological function of the distributaries of the Yangtze River; and the west coastal areas, especially the surrounding areas of Chongqing city with lower biomass per hectare. Also, the carbon-fixation function of the forest was used to analyze the service function of the forest ecosystem; thereby the forest ecosystem health level in the researched area was indirectly evaluated.In this dissertation, the evaluation on the stability of forest ecosystem in Three-Gorge reservoir area was mainly based on analysis of the two major factors, that is forest fire and forest disease and insect pests, and the integrated value of fire resistance ability of the tree species was used as the evaluation indicator and brought into the evaluation system. Based on the vegetation investigation and analysis on the combustibility of main fuel type, the integrated evaluation value on fire resistance in all subcompartments were determined, the results showed that the area with easily combustible forest type account for 46% of the total forest area; and the areas of combustible forest type and hardly combustible forest type account for 48% and 6% respectively. Therefore, it is very necessary to reduce the forest fire danger rating in Three-Gorge reservoir area by combining the forest health management.On this basis, according to the concept model of forest ecosystem health, from the perspective of vigor, organization structure, resistance ability and restoration ability of forest ecosystem, values of health index for every subcompartments of the second level forest resources investigation were calculated respectively, and the integrated evaluation on the forest ecosystem was given in the whole Three-Gorge reservoir area. And the threshold values of forest ecosystem were determined based on the field investigation data, also took the observing data as the reference for the threshold evaluation, the degree which away from the healthy status for every subcompartments were calculated. The determination of the health threshold value is the key to evaluate the health degree of a forest ecosystem, and this provided a quantified basis for the management and forecast of the forest ecosystem health in the Three-Gorge reservoir area.At last, from the perspective of forest landscape security, the multiple level evaluation indicator system was constructed according to the Analytical Hierarchy Process (AHP), and the quantified evaluation was given on the forest landscape security patterns in Three-Gorge reservoir area. The effect of forest landscape fragmentation degree, biodiversity, integrity and stability on the regional forest landscape security pattern were analyzed, its main objective is to evaluate the probably damage on forest ecosystem and its components which caused by the uncertain disasters and events. According to the order of the integrated evaluation value, Xingshan County, Shizhu County, Wulong County, Zigui County all have the evaluation value over 10, and the Xingshan County with the highest one, and the integrated evaluation value is 11.553. Badong County, Fengjie County and Yiling County also have relative higher values, the Chongqing city and surrounding areas, as well as the Wanzhou district with the lower values, the value of Chongqing and surrounding areas is 5.788, that means these areas have the lowest degree of landscape security, and the necessary measures should be taken to adjust and control the issues. All results provide a scientific basis on the enactment of correct forest ecosystem management plan both at landscape and regional scale in the studied area. |
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