Study On The Land Use Change In Dunhuang Xihu Based On Landsat Images

As the most basic elements of human activities,land is impacted profoundly by human activities.With the economy growsand the population increases,land use types are frequently changed,which generates not only a series of ecological and environmental problems,but also the gradually deteriorating ecological environment.In the northwest of China,the ecological environment problem is particularly outstanding.At the same time,with the development of remote sensing and GIS technology,the land use type survey based on the traditional method is gradually replaced by it.Research object of this article is the Dunhuang West Lake wetland in Gansu Province,which located in the fragile ecological environment in China.The Landsat series images(TM and OLI)between 1986 and 2015 are the main data sources.Using decision tree and object-oriented remote sensing image classification method,with the help of ENVI,Arcgis,eCognition and other softwares,the land use types of study area is extracted.Furthermore,the change of land use type is analyzed by area transfer matrix method,and the influencing factors that may cause the change are analyzed synthetically.The main contents of this paper include:(1)Comparing the methods of decision tree with object-oriented classification,the overall accuracy of the object-oriented classification method is 91.9996% and the Kappa coefficient is 0.8946,which is higher than the overall accuracy of 89.4705% and Kappa coefficient of 0.8751 of the decision tree classification method.It is proved that the object-oriented classification based on low-resolution image also has better classification accuracy.(2)The land information of the multi-period remote sensing image is extracted by using the object-oriented classification method.Results showed that the area of mobile dunes,bare land and Gobi accounted for more than 70% of the total study area,and the areas of the vegetation,saline-alkali land and swamp wetlands are about 10%,5%,0.63%,respectively.(3)The calculation of the transfer matrix of the land use type information in the study area is carried out.The results showed that the areas of marsh wetland and saline-alkali soil gradually decreased and increased.The areas of marsh wetland decreased from 41.69km2 to 14.43km2 and saline-alkali soil increased from 203.07km2 to 344.64km2.The areas of Gobi,dry river bed remained stable,and the vegetation coverage and bare land area changed dynamically.High frequency area conversions are reflected in the following aspects: between the saline land and the bare and low vegetation coverage area;between the marsh wetland and high vegetation coverage area and bare land;between the high-medium vegetation cover area and the medium-low.(4)The correlation coefficient of land use type change with precipitation and temperature in the study area is analyzed.The correlation coefficient shows that no significant correlation was found between unused lands(such as the Gobi,mountain,moving dune)and the precipitation and temperature.The reduction of marsh wetland area and the increase of saline land area were mainly affected by human activities.The area of high vegetation coverage is affected by temperature,and the area of medium and low vegetation coverage is affected by precipitation.