大渡河上游地区土地覆被动态变化的尺度效应

The Scale Effect of Land Cover Dynamics in the Upper Reaches of the Dadu River

基于1967、1986、2000和2006年4期土地覆被数据,从50 m分辨率开始,按照50 m的间隔依次递增至2000 m,共生成40种粒度的格网,然后利用景观指数方法,对大渡河上游地区土地覆被随尺度变化的动态规律进行了分析。结果显示,800 m粒度能在准确保留土地覆被面积信息的同时,稳定地反映景观指数的变化规律,因此是分析该地区土地覆被及其变化典型特征的理想空间尺度。

Based on remote sensing imageries of 1967, 1986, 2000 and 2006, and 40 grains from 50 m to 2 000 m with 50 m interval, the scalar dynamics of land cover change in the upper reaches of the Dadu River is analyzed through landscape metrics. The results show that： 1 ） Area precisions of different land cover types are significantly affected by scales. When grain changes at the range of 50 - 1000 m, the proportions of area in each land cover type to total area are consistent, however, a big difference in the proportions occurs when grain is bigger than 1000 m. 2） Landscape metrics have obvious ＂grain effect＂. When grain changes between 50m and 80Ore, the values of landscape metrics such as number of patch （NP）, total edge length （TE）, contagion index （CONTAG）and landscape shape index （LSI）decrease along with; when larger than 800 m, the decreases slow down. 3） Fractal dimension has obvious scalar features at landscape level. It increases with the increased spatial scales during the whole periods. When grain changes at the range of 50 -500 m, the fractal dimension monotonously increases rapidly; when grain changes between 500 m and 800 m, the increase becomes general, and further more, when grain is between 800 m to 2 000 m, the fractal dimension becomes stable. Combined with the changing trends of land cover patterns, landscape metrics and fractal dimension, we conclude that the grain of 800 m is an ideal scale which can keep relatively accurate area information and reflect typical features of land cover change in the study area.