Scale Analysis for Land Use Monitoring in the Main Stream of the Tarim River
2007, 22 (5):
Selection of optimum scales is one of the key issues in the studies of ecology,geography,etc.Scale laws for land use monitoring need to be found out in different periods.The natural ecosystems are seriously degenerated in the Tarim River Basin,which was paid great attention.In this study,the scale change laws of general land use and four main land use types including woodlands,shrubbery lands,sandy lands and saline or alkaline lands in the main stream area of the Tarim River are lucubrated by interpreting the land use data in the 1950s and in 2000 using the available maps and RS images.By regarding the areas of land use types as the scales,the parameters are selected,the histograms of the areas of patches are charted,the normalized scale variances at 9 scales (1:2000000,1:1000000,1:500000,1:250000,1:100000,1:50000,1:25000,1:10000 and 1:5000) are calculated,and the spatial distribution features and scale change laws of land use in the Tarim River Basin are lucubrated using normalized scale variances.Furthermore,sensitivity of land type with scale change is analyzed.The results are as follows:(1)The difference in areas of patches in the main stream area of the Tarim River is in great disparity,the patch of sandlands is the largest and its proportion in the year of 2000 was 43.77%.(2)The frequency distribution of the areas of patches,sandlands,saline or alkaline lands,woodlands and shrubbery lands in the main stream area of the Tarim River in the two study periods was in normal distribution,however,the positions of peak values and the distribution patterns were different,the positions of the peak values of sandlands and saline lands in the year of 2000 were in a range of 0.1～1km2 and those of others were in a range of 1～10km2.(3)The normalized scale variance figure reveals that most suitable scale of land use in general in the main stream area of the Tarim River is at 1:50000 or in a range of 1:50000～1:100000.Expect for the optimal scale of sandlands at a scale of 1:100000,the optimal scale of saline,woodlands and shrubbery lands is at a scale of 1:50000.The figures of normalized scale variances in the two study periods reveal that the change of the normalized scale variances of sandlands was tempestuous and was significantly higher than those of other land use types and; sensitivity of shrubbery lands was the highest,and then woodlands,saline and sandlands.Scale change rate was higher in 2000 than in the 1950s’.It was found that sensitivity of saline,woodlands and shrubbery lands showed a marked increase in 2000.On the contrary,sensitivity of sandlands decreased in 2000.
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