Choice of Appropriate Scale for Land Use Monitoring: A Case of the Tarim River Basin
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 (1:2000000, 1:1000000, 1:500000, 1: 250000, 1:100000, 1:50000, 1:25000, 1:10000 and 1:5000), 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 1:50000 in the 1950s, that 20km × 20km grid sizes, diversity of patch size at 1:50000 richer than in other scale's, so 1:50000 used as appropriate scale of the Tarim River. In addition to appropriate scale of sandy land at scale of 1:100000, the optimal scale of woodland, shrub land and saline land is at 1:50000. (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 1:10000 rather than 1:50 000. (3) Fractal dimension of sandy land and saline land showed a marked increase and up to 1.35 at 1:10000 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 1:10000, while woodlands and shruby lands's are distributed under the same hierarchical structure in the region.
appropriate scaleland use monitoringnormalized scale variancelandscape indexesTarim River Basin
NETL
NSTL
万方数据
维普
