喀斯特小流域土壤饱和导水率垂直分布特征

VERTICAL DISTRIBUTION OF SOIL SATURATED HYDRAULIC CONDUCTIVITY IN A SMALL KARST CATCHMENT

土壤剖面饱和导水率（Saturated hydraulic conductivity, Ks）的垂直分布对土壤水文过程有极其重要的影响，但在地质背景特殊的喀斯特地区其研究还相对匮乏。通过测定典型喀斯特小流域内 23 个土壤剖面（0～10、10～20、20～30、30～50、50～70、70～100 cm）土壤 Ks及土壤碎石含量（Rock fragment content, RC）、容重（Bulkdensity, BD）、毛管孔隙度（Capillary porosity, CP）、非毛管孔隙度（Non-capillary porosity, NCP）、土壤有机碳（Soilorganic carbon, SOC）等土壤性质，并结合各样点的坡位（Slope position, SP）、坡度（Slope gradient, SG）、坡向（Slopeaspect, SA）、裸岩率（Bare rock, BR）、土地利用类型（Land-use type, LU）等环境因素，应用偏相关分析和典范对应分析（CCA）的方法，研究了喀斯特小流域 Ks的垂直分布特征及其主要影响因素。结果表明， Ks随土壤深度的增加而减小并可用对数函数模拟（R2=0.848）。20～100 cm 各层 Ks变幅较小且变异接近，因此在水文模型中可用 20～30 cm 土壤 Ks代替深层。土壤性质中，RC 与 Ks的相关系数（0.484）最大。而环境因素对 Ks垂直分布的影响依次为SP 〉 SG 〉 SA 〉 LU 〉 BR。由此可知，RC 是影响 Ks最重要的土壤性质，而 SP 则是影响 Ks垂直分布最重要的环境因素。该结果有利于弄清喀斯特地区降雨入渗规律及其主要影响因素，为小流域植被恢复及水文模型的构建提供科学依据。

Vertical distribution of saturated hydraulic conductivity （Ks） has an important influence on soil hydrological processes. However, relatively speaking, few reports are available on this issue in karst areas with special geologic background. To study vertical distribution of soil saturated hydraulic conductivity （ Ks ） and its influencing factors in a small karst catchment, soil samples were collected from 23 soil profiles at 0 ~ 10, 10 - 20, 20 - 30, 30 - 50, 50 ~ 70 and 70 - 100 cm soil layers for measurement of Ks, rock fragment content （ RC ） , bulk density （ BD ） , capillary porosity （CP） , non-capillary porosity （ NCP ） and soil organic carbon （SOC） . Besides, environmental factors including slop position （SP） , slope gradient （SG） , slope aspect （SA） , bare rock （BR） and land use type （LU） were investigated at each soil profile site, and all the data obtained were analyzed with the partial correlation analysis and canonical correspondence analysis （CCA） methods. Results show that Ks generally decreased with increasing soil depth and the variation could be fitted with a logarithmic function （ R2=0.848 ） . The variation of Ks in the soil layers within 20- 100 cm was low in amplitude and approximate to each other, which indicates that Ks in the 20 - 30 cm soil layer could be used to represent Ks in the underlying horizons in building hydrological models. Among the soil properties, RC displayed the highest correlation coefficient （0.484） with Ks. In terms of influences of the environmental factors on vertical distribution of K~, a decreasing order of SP 〉 SG 〉 SA 〉 LU 〉 BR was found. It is, hence quite obvious that RC is the most important soil property and SP the dominant environmental factor that influences vertical distribution of K,. The findings help understand the laws and major influencing factors of rainfall infiltration and also provide some scientific basis for vegetation restoration in small karst catchments and for building of hydrological models, as well.