| Human activities and climate change continue to transform layout and structure of the ecological system, that cause changes in ecosystem function on different scales.Forest ecological system as the most important terrestrial ecosystems are badly affected. With the study of ecosystem of globalization,People begin to pay more attention to the forest landscape pattern in large scale range of the change of time and space. And river basin is important geographical unit which is as macro-scale regional environment, that has very profoundly influence to the regional ecological environment. Study on the Yangtze river basin is based on IGBP DISCCOVER data (1992),MODIS data(2001-2012) and relevant technology such as ArcGIS,ERDAS and FRAGSTAT.Research on the dynamic change and driving force factors of forest landscape pattern for1992,2002,2007,2012year in the Yangtze river,in order to provide the basis for river basin management of forest landscape.The research prove that:(1)The period of1992to2012,the forest,cropland and grassland is the most important landscape types of the Yangtze river basin, that cover more than3/5in the study area. Among them, the forest land area occupies the study area,that grow from21%in1992to37%in2012.Woodland mixed forest area occupies the study area,that grow from54%in1992to92%in2012,the rest of the forest land types is small.The landscape pattern change trend in1992,2002,2007,2012:grassland decrease after growth,cropland is decreasing gradually,woodland decrease after growth,wetland reduce gradually, ourban increase by yearly, bare land and others grow after decreasing.(2)From1992to2012, mixed forests,grassland,shurland and Deciduous Needleleaf forest have the larger variable quantity in forest.Among them,area of the mixed forest continue to increase and annual variation is the largest,the data is21443.24km2/year,Evergreen broad-leaved forest area is increased but the minimum annual variation, the data is18.50km2/year.Area of mixed forest area changes drastically because of biggest change in different periods.Evergreen Annual variation of Needleleaf forest and urban land area is negative and show a trend of decline year by year.Annual variation of other landscape types change fluctly,and shrubland,cropland and grassland is larger,that is associated with area.Overall,the dynamic change degree of Evergreen Needleleaf forest and grassland is least,while mixed and urban is largest(3)The total area of the transfer of various landscape types in1992-2002is897451.00km2,that account for0.4948%of the study area.The total area of the transfer of various landscape types in2002-2007is576304.50km2,that account for0.3177%of the study area.The total area of the transfer of various landscape types in2007-2012is1781172.25km2,that account for0.9819%of the study area The largest transfer area of various landscape types is grassland,cropland,mixed forests and shrubland because of their larger area.Evergreen Needlelea forest,Evergreen Broadleaf forest,Deciduous Broadleaf forest and Deciduous Broadleaf forest occupied lesser area,that mainly transfer to the mixed forest.And the structure of mixed forest transfer to be complex.The exchange of between shrublands and grassland is more obvious.The landscape types which transfer to cropland is mainly concentrated in the grasslands,shrubland, mixed forests and wetland.Urban that cover least of the study area and image correction may causes transformation unconspicuously.(4)The change in patch type level of the landscape types in Yangtze river basin show that the same trend of number of patches (NP) and patch density (PD) which decrease after increasing. And various types of landscape patch density (PD) is less than0.1,that show the landscape type consists of large area of patch.The boundary density (ED) of grassland,mixed forest, Evergreen Broadleaf forest and Deciduous Broadleaf forest is higher than other landscape types,that show higher degree of separation and broken than other landscape types.The average shape index (SHAPE_MN) and average dimension (FRAC_MN) have the same change trend,the minimum value of dDeciduous Needleleaf forest show decreasing.And compared with other landscape types show simple rulesand the complexity is decreased gradually.(5)The change in landscape level of the landscape types in Yangtze river basin show that number of patches (NP) and patch density (PD) decrease after growth, the average patch area (AREA_MN) and the largest patch index (LPI) increase after decline from1992to2012,showing that degree of landscape fragmentation increase from1992 to2002,gradually reduce and flatten out from2002to2012and landscape patch area tend to be homogenization.Boundary density (ED),average dimension (FRAC_MN) and landscape shape index (LSI) trend to decline after increase,showing that the landscape type separation degree,edge effect andl andscape type of interaction aggravate before they reduce;Average near distance (ENN_MN) increase after falling, shannon evenness index (SHEI),spread and parallel index (IJI),shannon diversity index (SHDI),distribute and parallel index (IJI) decline year by year,showing that the regional landscape diversity and uniformity,the landscape heterogeneity landscape diversity in the Yangtze river basin reduce gradually.(6)This researth on the relationship between landscape pattern changes and driving factors from1992to2012in Yangtze river basin show that the growth of the population,the increase of urban population,the development of the economy and the increase of per capita GDP,the decline of proportion in the first industry drops largely affects the distribution and change of forest in Yangtze river basin.And the influence of climate factors are relatively small,the lower correlation between rainfall and temperature show that the influence of raifall is smaller than the temperature.And analysis of multivariate linear regression model show that three factors of the social and economic factors including regional population,urban population,per GDP have largest impact on the change of landscape types.To sum up,the natural environment determines the distribution pattern of the landscape types, and social and economic factors including policy is the leading factor in the landscape pattern change. |
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