喀斯特坡面表层土壤含水量、容重和饱和导水率的空间变异特征

Spatial variation characteristics of surface soil water content,bulk density and saturated hydraulic conductivity on Karst slopes

表层土壤水分物理性质对深层土壤水分的动态变化具有重要的作用，研究其空间变化特征有助于深入理解坡地降雨入渗及产流规律，实现土壤水资源的合理利用．基于网格（10m×10m）取样，用地统计学方法研究了桂西北喀斯特地区典型灌丛坡地90m×120m（投影长）表层（0-10cm）土壤含水量、容重和饱和导水率的空间变异特征．结果表明：研究区土壤含水量、容重和饱和导水率均具有明显的空间依赖性和空间结构．土壤水分含量半变异函数用高斯模型模拟较好，土壤容重与饱和导水率用指数模型拟合较好．土壤含水量表现为强烈的空间自相关性，土壤容重和导水率表现为中等的空间自相关性．土壤含水量与饱和导水率空间连续性的尺度范围较小，而土壤容重空间连续性的尺度范围较大．总体上土壤含水量沿坡向下呈递增趋势，土壤容重呈递减趋势，而土壤饱和导水率沿坡面没有明显变化规律，斑块小而多，表现为高异质性．土壤含水量与土壤容重、饱和导水率均呈极显著负相关，而土壤容重与饱和导水率之间没有明显的相关性．

Surface soil water-physical properties play a decisive role in the dynamics of deep soil water. Knowledge of their spatial variation is helpful in understanding the processes of rainfall infil- tration and runoff generation, which will contribute to the reasonable utilization of soil water re- sources in mountainous areas. Based on a grid sampling scheme （10 m×10 m） and geostatistical methods, this paper aimed to study the spatial variability of surface （0-10 cm） soil water content, soil bulk density and saturated hydraulic conductivity on a typical shrub slope （90 m×120 m, pro- jected length） in Karst area of northwest Guangxi, southwest China. The results showed that the surface soil water content, bulk density and saturated hydraulic conductivity had different spatial dependence and spatial structure. Sample variogram of the soil water content was fitted well by Gaussian models with the nugget effect, while soil bulk density and saturated hydraulic conductivity were fitted well by exponential models with the nugget effect. Variability of soil water content showed strong spatial dependence, while the soil bulk density and saturated hydraulic conductivity showed moderate spatial dependence. The spatial ranges of the soil water content and saturated hy- draulic conductivity were small, while that of the soil bulk density was much bigger. In general, the soil water content increased with the increase of altitude while it was opposite for the soil bulk densi-ty. However, the soil saturated hydraulic conductivity had a random distribution of large amounts of small patches, showing high spatial heterogeneity. Soil water content negatively （P〈0.01 ） correla- ted with the bulk density and saturated hydraulic conductivity, while there was no significant corre- lation between the soil bulk density and saturated hydraulic conductivity.