Quantitative Research On Spatial-temporal Changes And Driving Forces Of Desertification In Chongqing

Desertification is one of the most serious ecological environment issues all over the world,which not only affects the current ecological environment of human life,but also poses a serious threat to the sustainable development of the Earth.The study of desertification will help to accurately grasp the dynamic changes and driving factors of desertification,and provide theoretical support for the governance of regional desertification.Most studies on desertification in China are concentrated in the northwest region.However,in recent years,desertification in the south areas has gradually attracted attention.As one of China's four municipalities directly under the central government,Chongqing has experienced rapid economic development since the new century,and its demand for resources has grown.The issue of desertification has also gradually attracted attention.In this study,four desertification evaluation indexes were selected,and the weight was determined by analytic hierarchy process(AHP).The desertification was evaluated from pixel scale in the Chongqing area from 2000 to 2015 years.Desertification was classified according to the evaluation results,and the changes in the interannual spatio-temporal process of desertification and the temporal and spatial changes of 5 years were analyzed respectively.In the quantitative research of the driving forces of desertification,the Pearson correlation coefficient was used to quantitatively research the single factor driving force of desertification,and the positive and negative correlations between each driving factor and desertification comprehensive value were obtained.Using the grey correlation method to do quantitative research on the comprehensive driving forces of desertification,the main driving factors for desertification are obtained,which provides scientific basis for the prevention and control of desertification in Chongqing.The main research results are as follows:(1)According to the existing research results and the actual situation in the study area,the selection principle of Chongqing desertification evaluation index is determined.On this basis,four indexes of desertification evaluation index system are constructed,including vegetation coverage,soil texture,valley density and slope.(2)The weight of desertification evaluation index is determined by analytic hierarchy process(AHP),and combining with four standardized evaluation indicators to evaluate desertification in Chongqing.Based on existing studies,desertification evaluation results are classified into four categories:severe desertification,moderate desertification,mild desertification and non-desertification.According to the distribution map of desertification,the desertification distribution areas in Chongqing from 2000 to 2015 years are roughly the same each year,mainly distributed in Kai-zhou,Yunyang,Wanzhou,Zhongxian,Fengdu,Pengshui,Qijiang,Youyang,Tongnan and Jiangjin.The desertification area statistics show that mild desertification accounts for more than 60%of the total desertification,while the severe desertification area is less than 6%.The area of desertification showed a downward trend as a whole.(3)By analyzing the spatial-temporal changes of desertification through the transfer matrix,the area of desertification improvement from 2000 to 2005 years was20961.6 km~2,accounting for 25.4%of the total area of the study area,and the area of desertification degradation area was 2984.1 km~2,accounting for 3.6%of the total area of the study area;the area of desertification improvement in 2005 to 2010 years was8926.1 km~2,accounting for 10.8%of the total area of the study area;and the area of desertification degradation was 5751.8 km~2,accounting for 7%of the total area of the study area;the area of desertification improvement from 2010 to 2015 years was7477.4 km~2,accounting for 9.1%of the total area of the study area;and the area of desertification degradation was 5818.9 km~2,accounting for 7.1%of the total area of the study area.According to the statistical results,it can be seen that in 2000 to 2015years,the area of desertification improvement has been getting smaller and the area of degraded desertification has been increasing,but the area of desertification improvement is larger than the area of desertification degradation,so the area of desertification as a whole still shows a downward trend.(4)Through quantitative research on driving forces of desertification in Chongqing.It was found that from the single factor driving force,the average temperature,precipitation,maximum wind speed,per capita GDP,the total output value of agriculture,forestry and animal husbandry,and the total industrial output value were positively related to the integrated value of desertification,and the overall negative correlation was the sunshine hours,relative humidity and population density.The positive correlation of this study shows that the greater the value of the driving factor,the greater the integrated value of desertification and the lighter the degree of desertification.The above factors are classified into two categories of nature and social economy.On the whole,the impact of natural factor driving force on desertification in the 2000 to 2015 years Chongqing area is slightly greater than that of socioeconomic factors,but in some years(for example,2007 to 2009 years),the driving force of socioeconomic factors has a greater impact on desertification.