广西岩溶区不同植被类型土壤水分特征及影响因素

目的]了解岩溶区不同植被覆盖下的土壤水分特征曲线及其影响因素,为岩溶山区土壤水分运动的定量分析提供理论依据。方法]通过野外调查与室内分析,研究广西平果果化典型岩溶峰丛洼地荒地、草地、灌丛、林灌4种不同植被覆盖下的土壤水分特征曲线。结果]van Genuchten模型、Brooks—Corey模型和Gardner 3种模型对土壤水分特征曲线的拟合效果都很好,相关系数均在0.93以上,且残差平方和都小于0.000 5,但van Genuchten模型的拟合效果最好;土壤持水能力与植被的正向演替、饱和含水量、非毛管孔隙度、粉粒含量显著负相关,与土壤容重、黏粒含量、毛管孔隙度、初始含水量和毛管含水量极显著正相关;不同植被类型,相同吸力下,表层和底层土壤的持水能力最强,中间土层的持水能力较差;不同土层深度,相同吸力下,荒地的持水能力最强,林灌的持水能力最差。结论]同一吸力下的土壤持水能力呈现出随植被的正向演替而不断降低的趋势;研究区影响土壤水分特征曲线的主导因素是非毛管孔隙度。

Soil Water Characteristics and Its Influence Factors of Different Vegetation Types in Karst Area of Guangxi Zhuang Autonomous Region

Objective] The aim of this study is to investigate the soil water characteristic curve and its influence factors under different vegetation cover in karst area in order to provide the theoretical basis for the quantitative analysis of soil water movement in karst mountain area.Methods] Based on field survey and laboratory analysis, this paper studied the soil water characteristic curve of four different vegetation type(wasteland, grassland, bushwood and forest-shrub) in typical karst mountains in Guohua, Pinguo, Guangxi Zhuang Autonomous Region.Results] All the three models including van Genuchten, Brooks-Corey and Gardner fitted the data well, with correlation coefficients were >0.93 and the sum of squared residuals were <0.0005. Among the three models, van Genuchten model was the best fitted model for calculating the soil water characteristic curve. The soil water-holding capacity showed a significant negative relationship with the positive succession of vegetation, saturated water content, non-capillary porosity and particle content, while it showed an extremely significant positive relationship with soil bulk density, clay content, capillary porosity, initial water content and capillary moisture. Under different vegetation types and the same suction, the soil water-holding ability was great at the surface and deep layer soil but poor in the middle layer soil. Under different soil depth and the same suction, the soil water-holding ability in wasteland was the greatest, while it was the poorest in forest-shrub.Conclusion] Under different soil depth and the same suction, the soil water-holding ability decreases with the positive succession of the vegetation. The dominant factor that influences the soil water characteristic curve in the study area is soil capillary porosity.