喀斯特地区典型峰丛洼地表层土壤水分空间变异及合理取样数研究

Spatial Variability of Soil Moisture Content and Reasonable Sampling Number in Cluster-Peak Depression Areas of Karst Region

在桂西北喀斯特洼地90m×40m地块范围内。用经典统计和地统计分析方法探讨了表层土壤（0～5，5～10，10～20，20～30cm）水分的空间变异结构及其分布格局，并给出了不同置信水平和精度条件下的合理取样数。结果表明：表层土壤水分总体上具有良好的半方差结构，呈明显的斑块状分布格局。0～5cm层具有中等的空间相关性，其余各层具有强烈的空间相关性，而且变异程度具有明显层次性；除20～30cm层土壤水分用球状模型拟合外，其余各层均符合指数模型，且拟合效果较好。等值线图结合半方差分析可以看出，地形、微地貌、降雨和植被等是研究区土壤水分空间变异的重要影响因素。在确定合理取样数的过程中，除考虑土壤水分的统计特征外还要考虑其空间结构性。

In the cluster-peak depression areas at northwest Guangxi, soil moisture content at surface layers （0～ 5,5～10,10～20,20～ 30 cm） was measured in a rectangular area （90m × 40m）. The spatial variability construction and distributing pattern were discussed by using the traditional statistics and geo-statistics, and the reasonable sampling numbers were calculated under different believable level and precision for all layers. The results showed that soil moisture contents at all layers had good semi-variance structure and its spatial pattern came out as obvious patches. Soil layer of 0～5 cm had medium spatial correlation, and the other layers had strong one. And the extent of spatial variability of soil moisture changed with layers. The first three soil layers could be well expressed by exponential models, but the last layer （20～ 30 cm） was simulated with spherical model. The soil moisture spatial variability in this region mostly contributed to the influencing factors, such as topography, micro-physiognomy, rainfall and vegetation from the analysis of semi-variance and contour maps. Moreover, the traditional statistics could figure out the sampling numbers of soil moisture distinctly, but in practical applications, the spatial construction of soil moisture should also be considered.