京郊西北地区农地利用与景观格局时空特征

运用遥感与地理信息系统技术,对三年Landsat 1M多光谱遥感图像(1989年、1996年、2005年)进行解译判读,获取京郊西北地区各土地利用类型数据.运用土地利用程度时空演变模型、土地利用动态度模型、土地利用重心模型和景观生态学方法,对研究区1989～2005年间农用地利用及景观格局变化进行了分析.结果表明:农用地频繁流转,以耕地流失最为显著,去向主要为城市及建设用地,林地面积增加缓慢,沙荒地向林地转移明显:农用地各类型的新增速率远小于同期的转移速率,而城市及建设用地则相反;1989～1996年间研究区的综合土地利用动态变化率较1996～2005年间的大,变化集中表现在西北城郊过渡区域,城镇用地扩张导致耕地的利用重心不断向西偏南方向转移;研究区农用地景观破碎化程度在增加,各景观类型的平均斑块形状趋于分散和简单,景观多样性、景观均匀度旱现增加趋势,而景观优势度存逐渐减小.以利用农业用地为鲜明特征的城市化过程是影响北京西北地区景观格局演变的直接因素,城市及建设用地的不断扩张使得林地、耕地斑块的平均面积逐渐变小,景观格局连通性降低.

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.