农田土壤颗粒尺寸分布分维及颗粒体积分数的空间变异性

盐渍土膜下滴灌过程中的土壤理化性质存在空间变异性，对灌溉管理有一定影响。该文根据3个不同尺度下土壤采样及颗粒尺寸分布（PSD）测定结果，探讨了土壤PSD分维和颗粒体积分数之间的定量关系，分析了各尺度和综合尺度下土壤PSD分维和颗粒体积分数的经典统计特征和地质统计特征，根据颗粒体积分数的半方差函数计算了不同尺度颗粒体积分数的分形维，并做出了等值线图。研究表明，土壤PSD分维与黏粒的体积分数呈正相关关系，黏粒体积分数增大引起PSD分维增加的原因在于细颗粒的比表面积比粗颗粒的大；各尺度土壤PSD分维及颗粒体积分数均无强变异特征；不同尺度下土壤PSD分形维的半方差函数中块金和基台值均非常低；50 m尺度土壤PSD分维和黏粒体积分数的等值线图具有类似的集中度和走势，而砂粒体积分数和粉粒体积分数则具有相反的集中度和走势。该研究说明土壤PSD分维和颗粒体积分数都有一定的尺度依赖性。

Spatial variability of fractal dimension for soil particle size distribution and particle volume percentage in farmlands

The spatial variability of soil physico-chemical properties for saline soil was during drip irrigation under plastic mulch and it influenced irrigation management. In this paper, based on soil sampling and the measured results of soil particle size distributions (PSD) at three scales, the quantitative relationships between soil PSD fractal dimension and particle volume percentage were discussed. Their classic statistical and geo-statistical characteristics were analyzed at each scale and all scales. Fractal dimensions of particle volume percentages at different scales were determined according to the semi-variogram models of soil PSD, and the contour maps were drawn. The results showed that: there were positive correlations between soil PSD fractal dimensions and clay volume percentages. Because specific surface area of small particles was larger than that of big particles, the soil PSD fractal dimension increased when the clay volume percentage increased. There was no strong variability for both soil PSD fractal dimensions and particle volume percentages at each scale. In the semi-variogram models of soil PSD fractal dimensions at three scales, both the nuggets and the sills were very low. The concentration degree and trends in contour maps of soil PSD fractal dimensions and clay volume percentage at 50 m scale were similar, but for contour maps of sand volume percentages and silt volume percentages, the concentration degree and variation trends were opposite. This study showed that there were certain scale dependence of soil PSD fractal dimension and particle volume percentages.