A Comparative Study On The Change Of Landscape Pattern And Biodiversity In Moderate-Temperate Steppe Cities And Warm-Temperate Steppe Cities In Inner Mongolia

With the adjustment of industrial structure,economic development and rapid population growth,China enters the stage of rapid urbanization.Urban expansion not only changes the landscape pattern in regional areas and fringe areas,but also has a great impact on biodiversity.Urbanization has a significant impact on the landscape pattern and biodiversity of Inner Mongolia because of the rich landscape type and fragile ecological environment.The moderate-temperate steppe cities Xilinhot,Erenhot and warm-temperate steppe cities Dongsheng District and Kangbashi New District was selected as the object of this research.Based on landsat TM images and field Plant community survey,this paper mainly focused on the dynamic changes of landscape pattern in regional areas and fringe areas,and their impacts on biodiversity in moderate-temperate steppe cities and warm-temperate steppe cities.The main conclusions are as follows:(1)Urban expansion in moderate-temperate steppe cities and warm-temperate steppe cities leads to an increase in the area of construction land,and the landscape heterogeneity and fragmentation degree are enhanced,the connectivity between the patches is weakened.In moderate-temperate steppe cities,grassland is decreased and the fragmentation degree increase,cultivated land,forest land,construction land and unused land are increased,grassland changes into construction land,forest land and unused land.But in warm-temperate steppe cities,cultivated land,grassland and unused land are decreased,the fragmentation degree increase,the area and connectivity of forest land and construction land are increased.(2)Urban expansion in moderate-temperate steppe cities and warm-temperate steppe cities leads to an increase in the area and Patch cohesion index of construction land in fringe area.In moderate-temperate steppe cities,the fragmentation degree and heterogeneity degree in the urban fringe area are increased,the connectivity between the patches is weakened,and the patch shape tends to be regular.But the landscape fragmentation degree and heterogeneity degree become decreased when construction land is increased to the main landscape type.Meanwhile,urban expansion leads to a reduction of grassland and increase of unused land in fringe area in moderate-temperate steppe cities.There was no obvious pattern of landscape pattern change in fringe area during the process of urban expansion in warm-temperate steppe cities,grassland and unused land is reduced,and cultivated land where built-up area expand is decreased.(3)As the distance with city increased,the shape of each patch in fringe area in moderate-temperate steppe cities and warm-temperate steppe cities tends to be regular.Landscape fragmentation degree and heterogeneity degree decrease,Patch cohesion index increase in fringe area in moderate-temperate steppe cities.But there is no obvious rule of landscape fragmentation in warm-temperate steppe cities.(4)The species of plants in urban areas is significantly higher than natural communities in both moderate-temperate steppe cities and warm-temperate steppe cities.The proportion of herbaceous perennial in urban area is lower than natural community,but the proportion of the mesophyte is higher,and the hygrophyte appears in urban area.The species diversity in urban area is higher than natural community,but evenness index is lower.Plants in urban area are mainly concentrated in Leguminosae,Asteraceae,Poaceae and other worldwide family.The proportion of herbaceous perennial plants in urban area of moderate-temperate steppe cities is obviously lower than warm-temperate steppe cities.