| Forest ecosystem is the main body of earth ecosystem, which plays the immeasurable role in maintaining global carbon balance, ecological stability and alleviating global warming.The ecological vulnerability, sensitivity, forest carbon and carbon density of the forest landscape pattern are the basis of evaluating the contribution of the carbon cycle. Studying its spatial distribution characteristics, dynamic change and trend has important implications for understanding the global carbon balance and forest ecosystem stability.This paper is based on Wuzhishan’s remote sensing image data of 1998,2003, 2007, the forest resource survey data in 2010 and 1993,1998,2003,2008 four kind of inventory data. According to Landscape ecology,Sustainable forest management and theory and method of Statistics, I study these including the establishment of of landscape pattern type index, valuation of basin ecosystem sensitivity, construction of landscape type vulnerability index and ecologically fragile index model, prediction of forest landscape area, estimation of forest carbon storage and economic value of carbon sinks. The main contents and achievements are summarized as follow:(1) Selecting nine landscape pattern indexes, including aggregation index (AI), landscape shape index (LSI), separating degree (D), edge density (ED), shannon diversity index (SHDI), shannon evenness index (SHEI), fragmentation index (FN), the connection degree index (CONNECT), patch density (PD), I compute landscape pattern indexes of different forest landscape types in Wuzhishan city using fragstats3.4. Dynamic analysis of forest landscape pattern suggests:shape index of Broad-leaved mixed forest is 57.9017(the biggest) and shape index of non-forested land is 20.7077(the smallest)The distribution of landscape types tend to more even and complexity remains the same in the past 10 years.For different landscape types,patch density tend to increase and change of shape index and edge density are similiar.For forest landscape, the change of separating degree is small and the mutual influence between patches is less.The change of type between landscape patches is mostly through Yearly change of ladscape aggregation index is small.(2) Selecting four factors, including the slope, elevation, soil type, land cover types,as the evaluation factors of ecological sensitivity, I evaluate basin ecosystem sensitivity comprehensively using the analytic hierarchy process (AHP).The result shows:comparing three periods of distribution of ecosystem sensitivity, the extreme sensitive region and sensitive ecological region in Wuzhishan city mostly distribute in the north,the southwest and the central,and the sensitive region rapidly expends by 1.765 between 1998 and 2003.By contrast,the reason why the region has higher relevance with slope, elevationand soil type is that the altitude is high,the terrain is steep and the region prones to soil and water loss and rain erosion under the influence environment and natural conditions.No sensitive area and light sensitive area distribute mostly along the river,and decrease rapidly 23302 m2 in the past 5 years.The reason is likely human activities. Though the area change in moderate sensitive area is small,the fact that ecological sensitivity is reducing over time in the soutneast reflects the complexity of the ecological sensitivity change(3)Building the model of the landscape type fragile index and ecological vulnerability index, I calculate the landscape type vulnerability index and ecological fragile index using the factor analysis method to determine index weight.The result shows:the order ofl the vulnerability of landscape types is:Timber economic forest>Other brush-field>Hardwood forest>Arboret economic forest>Non-forestry land>S Light hardwoods>Broad-leaved mixed forest>Bamboo forest>Coniferous forests.The reason why Timber economic forest is senstive to environment and its stability is poorer is that the altitudeof its location is high, its aggregation index is low and its fragmentation index is big.Among these 9 landscape types, ecological vulnerability index of Coniferous forests is the smallest. Class I areas in 5 years increased by 8.7 times, and grade III area gradually reduced, and class I and II regions are mainly distributed in the high elevation and steep slope zone, the area by less human disturbance and ecological vulnerability is low. There are two main change regulations of Wuzhishan city ecological vulnerability:one is the two stage differentiation, namely, with the passage of time, area III region decreased, grade I and II District, district IV and V area increases; another is the V region gradually from a single to a multipolar differentiation.(4)Analyzing three periods(1998,2003,2007) of forest landscape in Wuzhishan city by means of GIS software space sampling and interpolation method of statistics, to generate the map of the ecological vulnerability grade distribution.The result shows that:In 1998, Wuzhishan city of Coniferous forests landscape fragmentation index, edge density index were higher than other landscape types, Hardwood forest landscape connectivity index is relatively large; Light hardwoods landscape connectivity and Broad-leaved mixed forest Landscape connectivity are relatively small, while other shrubs landscape connectivity maximum. Light hardwoods landscape patch, Broad-leaved mixed forest landscape patches and surrounding landscape patch connectivity are Poor, and Other brush-field landscape patches and surrounding landscape patches are better.Broad leaved mixed forest landscape shape index is the greatest, surrounding the most developed Broad-leaved mixed forest. Various kinds of Bamboo forest landscape indexes are in the medium.The landscape isolation of Timber economic forest and Arboret economic forest are all maximum,(5) Markov model and Grey level model make prediction on the area of eight forest landscapes, which are Broad-leaved mixed forest, Timber economic forest, Hardwood forest, Coniferae, Light hardwoods, Bamboo forest, Arboret economic forest and Other brush-field. These two models have their respective merits and demerits on prediction accuracy of different landscape types and they are both suitable for forecasting the area of landscape type in Wuzhishan City. In the coming decades, the areas of forest landscape type in Wuzhishan City are various, the sequence is Broad-leaved mixed forest>Timber economic forest>Hardwood forest> Coniferous forests>Light hardwoods>Bamboo forest>Arboret economic forest>Other brush-field(6) Analyzing its spatial distribution characteristics and change tendency by GIS, estimating forest vegetation carbon reserves in Wuzhishan city through using the method of biomass conversion factor of continuous function and estimating the carbon sink economic value through afforestation cost method.The analysis finds that:In 2010, the gross area of Wuzhishan City is 116054.7766hm2, gross carbon stocks is 6060938.32t(about 6.1t), the average density of carbon is 52.22t/hm2 and the total value of carbon sequestration is 1.65645 billion yuan. Together with the present situation of forest resources in the ares, carbon sink function will have a larger carbon economic benefits as time goes on.During 1993 and 2008, Wuzhishan forest vegetation carbon population distribution trend for performance Natural successionâ†'Natural succession supplemented, the succession of human disturbanceâ†'The succession of human disturbanceâ†'Human disturbance succession supplemented, natural succession; carbon change trend:Excellentâ†'goodâ†'badâ†'good, As people are strengthening ecological consciousness and the forestry projects are executing in Hainan province, forest vegetation carbon of Wuzhishan will gradually appear benign development trend. |
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