科尔沁不同类型沙地土壤水分在降水后的空间变异特征

Spatial variability of soil moisture after rainfall in different type sands of Horqin Sand

采用地统计学的方法,研究了科尔沁沙地受轻度干扰的沙质草场、禁牧半流动沙地和受重度干扰的丘间低地在降水后的土壤含水量空间变异性。结果表明,土壤含水量变异幅度是丘间低地>半流动沙地>沙质草场。半流动沙地和丘间低地的表层与亚表层土壤水分空间结构差异较小,但土壤水分空间变异性都要高于沙质草场表层。沙质草场表层与亚表层空间结构差异明显,两层土壤含水量变程分别为181.80 m4、.55 m,分维数为1.91、1.99,表层变异性小,亚表层变异性大。半流动沙地表层、亚表层的土壤含水量由随机因素引起的空间变异性,分别占各自总空间变异性的50%和48%,主要表现在1 m以下的小尺度范围内。丘间洼地两层土壤含水量变异特征差异较小,空间变异性大,土壤水分空间格局图表现出由洼地中心向四周递减的分布趋势,但存在一定的尺度范围。由于自然环境的改变和人类活动的干扰,影响着沙地植被、地形小尺度分布格局在大尺度上的配置格局,降水后的沙地土壤水分格局也发生相应的变化,而地形状况、植被条件和小尺度的人为局部干扰在该变化中有着深远的影响。

Spatial variability of soil moisture after rainfall in different type sands of Horqin Sand were studied by geostatistics approach. The results showed that soil moisture in light disturbed sandy grassland, undisturbed semi- mobile dune and heavy disturbed inter- dune bottomland, had distinctive variability and larger spatial change range of variability, after rainfall. The variability degree of soil moisture in three sands is in the order： sandy grassland 〉 semi - mobile dune 〉 inter- dune bottomland. The spatial correlation coefficient and range of soil moisture of sandy grassland, were 0.62 and 181.80 m at 0-20 cm and 0.98, 4.55 m at 20-40 cm, respectively. The difference of spatial variability between these two layers was striking. The degree of spatial variability between topsoil and sub - topsoil moisture in semi - mobile sand was less than that between the topsoil and subsoil of sandy grassland, and had a strong spatial dependence. Moreover, the spatial variability of topsoil and sub - topsoil moisture caused by stochastic factors accounted for 50% and 48% in the total spatial variability,respectively, mainly in the scale of one meter. However soil moisture after rainfall in inter - dune bottomland had obvious spatial structure and small difference in variability between the topsoil and sub - topsoil. Contour maps expressed the descended distribution trend from the center to the periphery, and this occurred only in certain scale distances. The variances of sandy ecosystems in Horqin Sand were mainly due to natural changes and human activities and the change of soil moisture was driven by rainfall. Landform, vegetation and the intensity of human disturbance, even in small scale, played profound role in soil moisture.