Study On Land Use Change And Its Driving Forces In Xichang City

The analysis of Land use change and its driving forces is one of the important contents of global change research.Research on Land use change and its driving forces can better understand the changes in land use and the main driving factors,and provide a basis for formulating countermeasures for land use in the study area.This study relies on the key laboratory of the Ministry of Education,the National Natural Science Foundation project and the Ministry of Education Humanities and Social Science Planning Fund project,and takes Xichang City in the southwestern part of Sichuan province as the research area,and selects the four remote sensing image data of 2000a,2005a,2010a and 2015a as data sources.with the support of the ENVI 5.2 and ArcGIS 10.3,the maximum likelihood method in the supervision classification is used to obtain the fourth phase Xichang City land use date combined with Google Earth high-resolution images and GPS field validation data;The basic characteristics and spatial pattern of land use change in Xichang City are analyzed by using the models of land use quantity change,land use attitude,land use degree comprehensive index and land use transfer matrix.Then,from 5 aspects of area,shape,density,dispersion and diversity,16 typical landscape pattern indexes are selected,and the land use landscape pattern under different geomorphological types is studied with the help of Fragstats 4.2;Finally,combined with natural,social and economic factors,the Geographic detector is used to analyze the land use change and its driving forces of Xichang City.The following conclusions were obtained:(1)The land use types of the Xichang city is mainly forest land,cultivated land and grassland,and their areas accounts for more than 60%of the total land area.From2000 to 2015a,the area of forest land and construction land increased by 4292.30 hm~2and 3292.92 hm~2,respectively.The area of unused land,grassland and cultivated land decreased by 970.40 hm~2,4040.46 hm~2 and 2938.55 hm~2,respectively,and the water body change was relatively small,reducing by 67.17 hm~2.(2)The change of land use in township towns has obvious difference.There are large changes of Township towns in land use types:the largest increase area of construction land and forest land was Xijiao Township(796.57 hm~2)and Yinchang Township(1299.83 hm~2).The largest reduction in cultivated land in Xijiao Township(920.69 hm~2);The grassland area in Yinchang Township decreased the most(1180.47hm~2),while the grassland area in Minsheng Township increased the most(362.63hm~2).The area of unused land in Yinchang Township decreased the most(195.60hm~2),while the area of unused land in Qiadi Township increased the most(110.09hm~2);the water area of each township changed little.(3)The spatial pattern of land use changes significantly,the land types have changed from each other,and the area of conversion has been 71,464.34 hm~2.The types of mutual conversion mainly include grassland to forest land,cultivated land to forest land,forest land conversion,forest land to grassland,farmland to grassland,grassland to cultivated land,and cultivated land to construction land.The converted area of cultivated land is the largest,with 22,509.33 hm~2,mainly transferred to forest land,and cultivated land transfer forest is widely distributed in the township areas of Xichang City;the forest land is the largest,with 25,106.49 hm~2,mainly transferred from grassland and cultivated land,and grassland transfer forest is mainly distributed in the northwest?southwest and southeast of the higher elevation,more vegetation areas of Xichang City.(4)The spatial and temporal dynamics of land use landscape patterns of different geomorphological types at the level of plaque type and landscape type are significant.From the area index point of view,in the plains,terraces,hills,small ups and downs of low mountains and small undulating alpine areas,cultivated land occupies an absolute advantage,is the dominant landscape of the region;in the middle and undulating middle and low mountains,medium undulating mountains,large undulating mountains and large undulating alpine areas,forest is the dominant landscape.From the density index,the density index of the construction land in plain is the largest;in the terraces,hills,middle and low undulating mountains,the largest density indicator is cultivated land;in small undulating mountains,medium undulating mountains,large ups and downs in mountainous areas,the largest density indicator is grassland;in medium and low undulating mountains,the largest density indicator is unused land;in large rolling mountains,the land use types with large density indexes fluctuate in different study periods.From the point of view of landscape shape index and dispersion index,the agglomeration degree of cultivated land is higher,the space connection is higher and the fragmentation degree is low in the plains,terraces,hills and small undulating areas,and the agglomeration degree of forest is higher,the space connection is higher and the fragmentation degree is low in the middle and undulating middle and high rolling mountains.From the diversity index,the Shannon Diversity Index and the Shannon Evenness Index show a downward trend in the middle and low undulating,high mountains and large ups and downs,while there is an upward trend in other geomorphological types,including the largest rise in the plain area,the highest degree of landscape fragmentation,the greatest degree of interference in human activities,and the increasing level of landscape diversity.(5)There are differences in the degree of influence of each driving factor on the spatial distribution of land use change.The influence of natural driving factor is relatively small than that of social economy,and the influence of social and economic driving factor is dominant,and the most influential drivers are the regional development index,the human disturbance index,the population and the farmer's per capita income;Some driving factors have significant differences in the spatial distribution of land use,the land use degree of different factors has differences,and the largest area of land development and utilization is distributed in different types or ranges of driving factors;land use change is the result of the interaction of various factors,and there is interaction between the driving factors,which is non-linear enhancement and mutual enhancement of land use change.