黄土高原退耕坡地土壤水分空间变异的尺度性研究

Scale-dependency of spatial variability of soil moisture on a degraded slope-land on the Loess Plateau

在面积60m×60m的坡地上采用2m×2m的网格进行高密度土壤水分测定,通过改变采样幅度和采样间距的“再采样”方法,选取变异系数、相关距离和Moran的I相关指数3个参数作为表征空间变异大小的指标,研究了尺度大小对土壤水分空间变异的影响。研究结果表明,随着采样幅度尺度在一定范围内的增大,土壤水分变异的特征参数如变异系数、相关距离和Moran的I相关指数都呈不同程度地增大;当采样间距增大时,变异系数和Moran的I相关指数没有变化,而相关距离却减小。

In order to explore the impacts of scale on the spatial variability of soil moisture, a study in a 60 m× 60 m sloping land area was carried out, spatial variation of soil moisture was analyzed with all the data measured under 2 m × 2 m sampling grid with TDR, then, re-sampling technique was employed with changing sampling extents and spacings, and spatial variation of each scenario was also determined. In the process of data analysis, three indices commonly used in spatial analysis including coefficient of variation, correlation length and Moran＇I index were applied to each scenario to characterize the degree of spatial variability of soil moisture, at the same time, some related issues of scale-dependency were discussed. The results showed that all the indices measured increased with various degrees with increasing extent. However, spacing did not affect coefficient of variation and Moran＇I index, while correlation length decreased with the increase of spacing.