喀斯特森林表层土壤持水能力空间分布特征及其影响因素

Spatial Distribution of Surface Soil Water-Holding Capacity in Karst Forests and Its Influencing Factors

[目的]探究喀斯特森林表层土壤持水能力空间分布特征及其影响因素,为提升该地区森林土壤水源涵养能力提供科学参考。[方法]以贵州省茂兰喀斯特原始森林表层土壤(0—10 cm)为研究对象,采用环刀法与室内浸泡法对土壤物理结构和持水特性进行测定,并利用方差分析、RDA分析等方法探究不同地形部位土壤持水能力空间分布差异及其影响因素。[结果]①土壤物理特征呈高异质性,土壤容重、土壤含水量、孔隙度、机械组成等在不同坡向、坡位和海拔间均具有显著性差异。②土壤持水率在不同坡向间差异最显著,土壤持水量在不同岩石裸露等级间差异最显著。土壤最大持水率、毛管持水率、饱和持水量与毛管持水量均随着坡位和海拔的增加而增加,且随着岩石裸露等级的下降而增加。土壤综合持水能力在低裸露、低海拔地区较好。③相关分析表明,地形特征、土壤物理特性与土壤持水率的相关性更强,林分特征与持水量的相关性更强,林分密度与持水量显著负相关,平均胸径、平均树高与持水量显著正相关。④PCA分析结果表明,土壤持水量是表征茂兰喀斯特森林表层土壤持水性能的第一主要因子,土壤持水率为第二主要因子,主成分一、二累计贡献率为77.5%。RDA分析结果表明,土壤孔隙度、岩石裸露等级是茂兰喀斯特森林表层土壤持水能力的主要影响因素。[结论]茂兰喀斯特森林土壤持水能力具有高异质性,在不同地形部位间差异显著,非毛细孔隙度(P nc)是影响土壤持水能力的主要因子。

[Objective]The spatial distribution characteristics and influencing factors of surface soil water-holding capacity were explored in a karst forest in order to provide scientific references for improving the water conservation capacity of forest soil in the region.[Methods]The surface soil(0—10 cm)of a primary Maolan karst forest in Guizhou Province was taken as the research object,and the physical structure and water-holding characteristics of soil were measured by the ring knife method and the indoor soaking method.The spatial distribution differences and influencing factors of soil water-holding capacity in different terrain locations were investigated by using variance analysis and RDA analysis.[Results]①Soil physical characteristics showed high heterogeneity,and soil bulk density,soil water content,porosity,and mechanical composition had significant differences in different slope directions,slope positions and altitudes.②Soil water retention had the most significant difference in different slope direction,and soil water retention had the most significant difference in different rock exposed grades.The maximum soil water-holding capacity,capillary water-holding capacity,saturated water-holding capacity,and capillary water-holding capacity increased with increasing slope position and elevation,and with decreasing rock exposure grade.The comprehensive water-holding capacity of soil was greater in the area of low exposure and low elevation.③Correlation analysis showed that topographic characteristics and soil physical characteristics were more strongly correlated with soil water-holding capacity;stand characteristics were more strongly correlated with water-holding capacity;stand density was significantly negatively correlated with water-holding capacity;and average DBH(diameter at breast height)and average tree height were significantly positively correlated with water-holding capacity.④The results of PCA analysis showed that soil water retention was the first main factor to represent the surface soil water retention performance of the Maolan karst forest,and soil water retention rate was the second main factor.The cumulative contribution rate of principal componentsⅠandⅡwas 77.5%.RDA analysis results showed that soil porosity and rock exposure grade were the main factors affecting the water-holding capacity of surface soil in the Maolan karst forest.[Conclusion]The soil water-holding capacity of the Maolan karst forest exhibited high heterogeneity and significant differences among different terrain locations,and non-capillary porosity(P nc)was the main factor affecting soil water-holding capacity.