| Desertification is a type of land degradation in which descending soil productivity and losing land resources.It is caused by a variety of factors,such as climate change and irrational human activities.At present,desertification has become one of the most serious problems in the word.Determining prevention method and measure by real-time dynamic monitoring and estimation for desertification land is of great signification for improving the ecological environment and managing the desertification land.Remote sensing technology has the characteristics of wide viewing angle,time-limited and low cost in desertification monitoring.Extracting land information by remote sensing technology,obtaining classification of degree of desertification land,making quantitative research has been the developing trend in desertification research field.West Jilin Province's land desertification phenomenon is serious,it has become the most serious area in Jilin Province.By combining objectbased classification methods,this paper extracted desertification land information in 1990,2000 and 2015 in the west of Jilin province,based on remote sensing data including Labdsat5 TM,Labdsat7 ETM+ and Landsat8 OLI.This article build the system of land classification index,divided the land into four levels.By using the function of “intersect” in ArcGIS,this study analyzed the current status,spatial and temporal change,driving forces and characteristics of regional differentiation.Finally,this paper support certain measures and proposals.The basic conclusions are concluded as follows:1.In 1990,study area's desertification land mass is 686178.76 ha,account for 14.63% of total area.In 2000,desertification land mass is 797081.14 ha,account for 17.00% of total area.In 2015,desertification land mass is 763454.95 ha,account for 16.28% of total area.The result shows that the area decreased at first and then increased,but the desertification land area in 2015 still larger than the area in 1990.There is more desertification land in central and southern regions than eastern and northern regions.2.From 1990 to 2015,the desertification land in west Jilin province increased firstly and then decreased.Nearly 70% bush fallow and 30% farmland occurred desertification in the expansion process.From the angle of classification,light decertified land was constantly expanding,moderate decertified land and heavy decertified land reduced first and then increased,serious decertified land increased first and then reduced.From the angle of desertification type,decertified bush fallow was constantly reducing,decertified farmland remained basically unchanged,activating sand dunes significantly increased.From 1990 to 2000,desertification land's dynamic degree is 1.62%,and it decreased to-0.28% from 2000-2015.Baicheng district's relative variation ratio is 0.021 and Songyuan district's relative variation ratio is 0.006,desertification land in Baicheng district reduced obviously.3.The change of desertification land is under the comprehensive influence of natural factors and human factors.Study area has sufficient sand source sediments which is the main reason of desertification.During the past 25 years,precipitation increased and wind speed decreased,which led to less sand deposition.1990-2000,severe overgrazing led to a large decrease in grassland,which is the main reason of desertification land expansion during that period.2000-2015,the rural population proportion in west Jilin province has a further reduction,from rural to urban,migration not only enhances the income of average family,but also shows less reliance on land.All these phenomena weaken the inter restricted relationship among population,resource and environment.In the meantime,the share of GDP produced by the first industrial fell dramatically,area's industry internal construct changes obviously.The share of GDP produced by agriculture becomes less,produced by animal husbandry and forestry become more,desertification problem had improved. |
PDF Full Text Request