Spatial and temporal characteristics of agricultural land-use and landscape pattern changes in northwest of Beijing

With the help of remote sensing(RS) from three period(1989, 1996 and 2005) Landsat TM images and geographical information system(GIS) technologies, the spatial and temporal change model of land-use, dynamic land use model, gravity-center model and landscape ecological method were used to analyze the landscape pattern and agricultural land use changes in northwest of Beijing. The results indicate that all types of agricultural land convert frequently and the tendency that farmland converts to urban and built-up land is the most obvious characteristic. The areas of forestland land increased slowly, and there is a significant shifting from sandy badlands to forestland. The newly-increased rates of all types of agricultural land is much less than the converted rates of them in the same period, but it is opposite for urban and built-up. Land-use comprehensive dynamic change rate from 1996 to 2005 is obviously smaller than that from 1989 to 1996, and changes mainly concentrate in rural-urban fringe. Owing to the urban land expansion, the transfer direction of gravity center of agricultural land use is southwest. The degree of fragmentation of agricultural landscape increases, the patch shape is dispersed and simplified, and the indices of landscape diversity and landscape evenness have the tendency of increase while the dominance decreased slightly. It can be concluded that rapid urbanization by occupying farmland becomes the direct factor affecting landscape pattern change in northwest of Beijing in China. The region in northwest Beijing has resulted in sharp decreases in mean patch size of forestland and farmland, agriculture land use type and landscape connectivity.