土地利用监测适宜尺度选择方法研究——以塔里木河流域为例

Choice of Appropriate Scale for Land Use Monitoring: A Case of the Tarim River Basin

适宜尺度选择是生态学、地理学等学科的重要问题之一。在不同的研究目的下,尺度选择的方法和标准也随之变化。以塔里木河流域20世纪50年代土地利用数据为例,将面积作为尺度选择的参数,统计斑块面积分布直方图,然后计算9种比例尺(1:2000000,1:1000000,1:500000,1:250000,1:100000,1:50000,1:25000,1:10000和1:5000)下的归一化尺度方差,最后结合Shannon-Weaver景观多样性指数、Simpson多样性指数和分维数补充归一化尺度方差的结果,探讨塔里木河流域土地利用的空间分布特征和尺度规律。结果如下:①归一化尺度方差值显示塔里木河干流50年代土地利用监测适宜尺度为1:50000比例尺(约20km×20km网格大小),除沙地适宜尺度在1:100000比例尺外,有林地、灌木林地和盐碱地的适宜比例尺均在1:50000比例尺上;②Shannon-Weaver多样性指数、Simpson多样性指数和分维数结果表明盐碱地的多样性指数的适宜尺度与归一化尺度方差结果相同,沙地的多样性指数与归一化尺度方差的适宜尺度域相同,有林地和灌木林地多样性指数最优尺度在1:10000比例尺与归一化尺度方差结果不同;③沙地和盐碱地的分维数在1:10000比例尺处有明显的上升,沙地达到最大值1.35,而在其他尺度分维数值接近,有林地和灌木林地则在各个尺度分维数值接近,且值不超过1.2。

After wastelands reclamation in the Tarim River Basin in recent 50 years, one third of the stream flow in the Tarim River （the longest continental river in China） has been cut off. The natural ecosystems are seriously degenerated, and the situation of land use is tempestuously changed. Therefore, it is urgent to resolve the problems that whether there exist the changing laws of scales and what kinds of scales are suitable in monitoring land use. Adaptive choice of scale is one of the important issues in ecology and geography. In different studies, the choice of methods and standards vary with purpose. This article summarized methods on how to choose appropriate scale based on land-use data of the Tarim River Basin in Xinjiang of China in the 1950s. Regarding the areas of land use types as the scales, the parameters are selected, the histograms of the areas of patches are charted, and then normalized scale variance calculated under 9 scales （1：2 000 000, 1：1 000 000, 1：500 000, 1： 250 000, 1：100 000, 1：50 000, 1：25 000, 1：10 000 and 1：5 000）, furthermore, some landscape indexes of patch area counted to examine and add result of normalized scale variance as well, which include Shannon-Weaver＇s landscape diversity index, Simpson＇s diversity index and fractal dimension respectively. The scale laws of general land use and 4 main land use types including woodlands, shrub land, sandy land and saline or alkaline lands in the mainstream area of the Tarim River are lucubrated by interpreting the land use data in the 1950s. The result showed that： （1） Normalized scale variance of the Tarim River reached maximum at scale of 1：50 000 in the 1950s, that 20km×20km grid sizes, diversity of patch size at 1：50 000 richer than in other scale＇s, so 1：50 000 used as appropriate scale of the Tarim River. In addition to appropriate scale of sandy land at scale of 1：100 000, the optimal scale of woodland, shrub land and saline land is at 1：50 000. （2） Shannon-Weaver＇s diversity index, Simpson＇s diversity index and fractal dimension of saline land have the same results as normalized scale variance. Diversity indexes and normalized scale variance of sand land proved the appropriate scale being in the same scale domain. It is noticed that there is a significant difference in woodland and shrub land. The optimal scale of diversity indexes are at 1：10 000 rather than 1：50 000. （3） Fractal dimension of sandy land and saline land showed a marked increase and up to 1.35 at 1：10 000 and similar at other levels, however, fractal dimension of woodland and shrub land are close at all scale levels and no more than 1.2, which reveals that hierarchical structure areas of sandy land and saline land are probably changed at scale of 1：10 000, while woodlands and shruby lands＇s are distributed under the same hierarchical structure in the region.