Spatio-temproai Variation Characteristics Of Desertification In Hulunbeier Sandy Land

Desertification is one of the most serious environmental and social problems the human society is facing.The development of the desertification threats human survival and development.The Hulunbeier sandy land is one of Chinese four big sandy land,and land desertification threat to the local social and economic development and ecological security and the surrounding area seriously under the joint action of natural and man-made.Therefore,combined with remote sensing technology to long-term monitoring of the hulunbuir sandy desertification,understanding its developing trend,it has important practical significance to grasp the dynamic change law.Based on the Hulunbeier sandy land as the study area and the landsat remote sensing data,the paper aims to monitor the Hulunbeier sandy desertification quantitatively using MSAVI,Albedo and MSDI index according to the principle of selection index system of desertification.Land desertification information including decertified land area,transfer matrix,the space distribution information,center of gravity shifting in 1982,1990,2000,1990,2000 are obtained,based on Landsat data of different sensors and decision tree model setting up corresponding different time.After precision verification,a kappa coefficient is above 0.86,showing that the method is feasible.On this basis,the spatial and temporal variation characteristics of desertification in the study area was analyzed,at the same time,the driving force of desertification land change was analyzed combined with the climate factors such as temperature,precipitation,wind speed,and other social and economic data including population,livestock,cultivated land,gross domestic product(GDP).Get the following main conclusions:(1)The time changes showed that desertification land change trend is the development and reverse coexist from 1982 to 2015,desertification area in 2015 was more than that in 1982,but a reverse trend occurred after 2000.Desertification land area expanded from 1982 to 1990,with the increasing area of 794.13 km~2 and the rate of 1.23%/a,and all levels of desertification land area had the development trend.From 1990 to 2000,desertification land area expanded stilly,with the increasing area of 3340.95km~2 and the rate of 3.87%/a,and all levels of desertification land area increased.However,the desertification land area in 2000-2010 decreased,with the area of 145.56 km~2 and the rate of 0.12%/a,which mainly caused by moderate desertification land area reduction,while other levels had increasing trend.Therefore,Desertification land area in partial had been controlled,while part of area was still in development.Desertification land area decreased from 2010 to 2015,with the area of 2186.93 km~2 and the rate of 3.59%/a,and all levels of the desertification land decreased,demonstrating that desertification got control in this period.(2)Spatial distribution,the land desertification in the study area are mainly distributed in the study area in the central and western regions.The mild and moderate desertification land is mainly distributed in the new barr tiger right flag;Severe and very severe desertification land is mainly distributed in new barr tiger left flag and Chen barr tiger flag in the western region.The spatial distribution of different levels of desertification land of center of gravity is from west to east,in turn,for mild,moderate,severe and severe desertification land.(3)Space change,desertification development(1982-1990)and reverse active region are mainly distributed in new barr tiger left flag,barr tiger right flag and Chen barr tiger flag.Mild desertified land during 1982-2015 weight 17.19 ? migrated to the northeast,moderate desertification land 20.33 ? center of gravity moving north-west,severe desertification land migration of center of gravity to the southwest of the 23.03 ?,extremely severe desertification land center migration distance is not big,9.43 ? moved towards the northeast.(4)Driving factors,the Hulunbuir sandy climate change trend can be seen that at the end of 1980 s to the 1990 s has a dry climate change trends,and uneven distribution of rainfall during the year,the spring wind speed less rainfall,at the same time,population,livestock and cultivated land area are constantly growth.Therefore,climate change and human activities are not conducive to reverse desertification.Since entering the 21 st century,the increase of precipitation,the decrease of cultivated land area and the implementation of the ecological protection and recovery policy promoted the reversal of desertified land.