湿润和干旱条件下喀斯特地区洼地表层土壤水分的空间变异性

在桂西北喀斯特洼地，用地统计学方法研究了旱季初期湿润和干旱条件下表层（0—5和5～10cm）土壤水分的空间结构及其分布特征．结果表明，表层土壤水分存在明显的空间异质性和各向异性，呈现差异显著的斑块状分布格局．湿润条件下，土壤水分具有中等和较强的空间相关性，变程分别为33．15n，和15．75m，其中0～5cm层具有明显的趋势效应；干旱条件下，土壤水分则呈现出强烈的空间相关性，而且相似斑块的空间尺度有所减小，变程最小仅为8．22m;在平均含水量较低时（干旱条件）其变异程度较大，实际应用中应根据平均含水量水平采取不同的取样设计．实验区表层土壤水分空间变异及其分布格局的显著差异，主要是受地貌、平均含水量（降水）和地形等因素的影响．

Spatial variability of surface soil moisture content in depression area of karst region under moist and arid conditions

By the methods of geostatistics, this paper studied the spatial structure and distribution pattern of surface soil (0 - 5 and 5 - 10 cm) moisture content in the depression area of karst region in northwest Guangxi under moist and arid conditions in the forepart of dry season. The results showed that in test area, surface soil moisture content had obvious spatial heterogeneity and anisotropy, presenting a significantly different plaque distribution pattern. Under moist condition, surface soil moisture content had a medium or stronger spatial relativity, with a range of about 33.15 and 15.75 m, respectively, and an obvious trend effect in 0 - 5 cm soil layer. Under arid condition, the spatial relativity was strong, and the spatial scale of resembling plaque had somewhat decrease, with the smallest range being 8.22 m. The moisture content under arid condition had a higher spatial variability, and thus, the sampling strategy should be based on the mean soil moisture content. The significant difference in the spatial variability and distribution pattern of surface soil moisture in test area was mainly due to the effects of physiognomy, soil mean moisture (precipitation), and topography.