| Datong City, located in the wind-water erosion crisscross margin region of loess plateau in Shanxi Province, is faced with serious soil/water loss and fast changes in the ground surface and ecological environment. Both nature and human factors cause the frequent and remarkable change of land cover and environment in Datong. It is necessary to analyze and estimate the land cover dynamics in order to promote the exploitation of land resources and ecological construction.In this study, four sets of Landsat TM/ETM+/OLI/TIRS image photoed in 1993, 2002,2009,2013 were used as main data sources. Majority voting in multiple classifiers was chosen to classify the remote sensing images, and land cover change in the latest 20 years were gained. In order to explore the land cover change rule, temporal and spatial variation features were analyzed from structure variation, quantitative variation and degree change. In order to analyze the features and variation of landscape in Datong, ten landscape pattern indexes were selected in plaque scale and landscape scale. Four ecological environment elements, including greenness, wetness, dryness and heat, were extracted to construct RSEI, which was used to evaluate ecological environment variation in Datong.The main research results are as follows:(1)The majority voting algorithm can effectively improve the remote sensing image classification performance in this region in comparison to other single classifier. It can not only enhance the classification precision and accuracy, but also access to the desired effect in the area classification.(2) The main classes in Datong are cultivated land, shrub, bare rock and forest land. Forest land, plantation, construction land area grew rapidly, and bare rock, bare soil, shrubs and grassland was reduced more. The results that conversion by ground objects conform to the trends of change of land cover. In recently two decades the natural vegetation in Datong decreased gradually, the artificial vegetation and construction increased annually, large area of unutilized land had a significant reduction. From 1993 to 2002, the shrubs and grass reduced rapidly.From 2002 to 2009, the forest and plantation growth accelerated,and arable land and construction growth slowed, from 2009 to 2013, the grassland continue increased, and the bare rock and bare soil decrease rapidly.(3)Patch number of water was the lowest. Grassland, shrub, cultivated land, bare rock dominated the patch numbers in four periods in Datong City. Mean patch size of cultivated land was the biggest. The trend of increase in mean patch size of cultivated land and decrease in mean patch size of shrubbery was obviously. Other types of plaque fragmentation was larger except for shrub, forest land and bare rock. The cultivated land had mean patch fractal dimensions,while patch shape was complicated for bigger fractal dimensions of forest land, shrub and grass land. During the whole study time, patch density, landscape shape index, shannon’s diversity index, SHEI showed a declining trend, while clumping index indicated a raising trend, which showed a decrease of landscape system diversity and some patch type played a dominate role in the whole landscape. Meanwhile, there was clumping trends in each patch type, therefore the distribution was centralized. All of these showed that the influence of human activities to land cover was dropping.(4) The means of RSEI in Datong city was similar in four periods, but the variance (steady Qualitative) gradually decreased toward the good and bad levels of development, and had significant differences in different regions. In the early, the area that eco-environment change to worse was larger, and later the area that eco-environment change to better was larger. All of them were increasing. |
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