| Red soil region in southern China which with high mountains and steep slopes,high rainfall intensity and rainfall amount,causing soil and water loss easily with populous but lack of land.As typical soil erosion control area in southern subtropical hilly area of China,Changting country was one of the most serious soil erosion areas in South China due to historical and natural reasons.The soil and water erosion control has experienced a long process,especially after the year 2000.The government invested more money and technology for the comprehensive management of soil and water loss in Changting.Identification of influence factors responsible for the dynamic change of fractional vegetation cover in Changting county are mainly common concern issues of soil and water conservation department,forestry management department and scientific research personnel.Fractional Vegetation Cover(FVC)refers to the vertical projection area of vegetation on the ground,which accounts for the percentage of the total area of the statistical area.The change of vegetation coverage had the impact of a system on soil erosion and agricultural development,ecological environmental,and also inevitably affects economic development a both locally and nationally.Study on the dynamics of local vegetation coverage is the effective measure to evaluate the regional control of soil and water loss and the restoration of ecological environment.Nowadays,many researches have been carried out on the spatial and temporal variation of FVC and its influencing factors.However,many studies focused on the factors of weather and terrain factors,and the analysis of human social and economic factors are not enough.In addition,the researches on the influence factors of fractional vegetation cover were mainly adopted the correlation analysis and multiple linear regression methods.This method assumes that the relationship between the factors and fractional vegetation cover are linear,so it is not able to reveal the complex nonlinear relationship between fractional vegetation cover and influence factors.Random forest is a nonparametric classification model,which is not limited by the assumption of linear return model has been widely used in the fields of biology in recent years.However,there are few reports about response factor criterion of fractional vegetation cover.Accordingly,this study had chose Changting country as the study area,and using Landsat Thematic Mapper(TM)remote sensing data that the spatial resolution is 30m and HJ-1 remote sensing data,the normalized difference vegetation indexes(NDVI)from 2000 to 2014 were collected to calculate the vegetation coverage Change of time and space in Changting,Fujian Province by the geographic information system(GIS)and the dimidiate pixel model and difference operation.This study used Random Forest algorithm to analyzed the spatial and temporal variation of fractional vegetation cover and the main factors affecting in soil and water lose governance typical area of Changting county in recent 11 years,aimed to reveal the key factors that affected the change of fractional vegetation cover in Changting country by considering the meteorological,topographical and social economic factors.In addition,we used the Mann-Kendall trend test to analysis the relevance with climate change and vegetation restore in Changting and reveal the effect of vegetation restoration on microclimate.The research would provide reference and decision-making basis for the vegetation and ecological restoration assessment and the future work of soil and water conservation in Changting county.The main conclusions were as follows:(1)During 15 years of the study(2000 to 2014)the NDVI value showed an upward trend.The medium and low,medium and high vegetation cover have been gradually transformed into high vegetation cover,with a significant increase.High vegetation coverage were mainly distributed in the north and west of the region,medium and low vegetation coverage were mainly distributed in central and southeast,especially on the two sides of Ting Rive.Changting vegetation changes was mainly for restore and fully restore,and the area which vegetation had severely degraded were mainly distributed on the two sides of Ting River.(2)It was concluded that the variance explanation rate of the dependent variables and the independent variables in Changting was higher in 2000-2010,the correlation of FVC between the observed value and predictive value was higher after analyzed with Random Forest Regression,the mean squared residuals was less than 0.01 and significantly related(P<0.01).Through importance ranking of the fractional vegetation cover and various independent variables had two different descending order,and obtained climate factors,social economic factors and population density had varying degrees of impact to Changting fractional vegetation coverage.(3)On the entire study area,temperature,precipitation,relative humidity,wind speed and the surface temperature change trended were similar to the controlled area of Pingnan,but the temperature,relative humidity and surface temperature had occur some delay of breaking points,and precipitation and wind speed were sudden changed in time same.Human development factors caused some damage to vegetation coverage,in turn,affects the change of meteorological factors.(4)In summary,after years of governance,Changting fractional vegetation cover had increased significantly,and the vegetation restoration effect is obvious,especially in the northwest of the high vegetation coverage area;there was also local area degraded mainly distributed in Ting River,due to the greater impact of human activities.On the whole,climate factors,social economic factors and human activities had great influence to fractional vegetation cover,and the increase of local fiscal expenditure and rural per capital net income had promoting effect to fractional vegetation cover.In addition,the growth of GDP,population density,and infrastructure will inhibit the growth of vegetation cover to some extent.The climate factors had an impact on vegetation coverage and the regional vegetation coverage will have a certain feedback effect on the climate.Envisage the reality that the artificial factors were the dominant ones is'conducive to further improve the soil and water conservation by step up publicity efforts and take as much as possible measures to perfect soil and water conservation,give full play to people subjective initiative to promote the development of the ecological environment.With the combination of soil erosion control,ecological environment construction,regional economic development and the improvement of people living standard,maintained the sustainable development of soil and water conservation and economic construction. |
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