喀斯特坡地土层厚度及养分含量空间分布特征

Spatial distribution characteristics of soil thickness and soil nutrient content in karst slopes

岩溶作用下,喀斯特坡地溶沟、溶槽普遍发育,岩土分布表现出极强的空间异质性,目前对土壤分布格局及其理化性质变异特征方面的认识还极其缺乏,这严重影响了该区有限水土资源的合理规划和高效利用。本研究通过在喀斯特坡地沿坡向上开挖12条土壤岩石样沟(长24 m,宽1 m),根据土岩结构和土层厚度将样沟分为浅薄土层、中层土层、深厚土层三种样沟类型,分别选取典型样沟,探讨了喀斯特坡地土层厚度及主要养分元素的空间格局特征。研究发现:喀斯特坡地土层厚度变异性较大,变异系数介于12.0%~85.3%之间,土层厚度介于0~430 cm之间。土壤肥力整体较低,综合肥力系数随土层深度增加逐渐减少,除0~10 cm深度土层土壤肥沃程度为一般外,10 cm以下土壤肥沃程度均属贫瘠,即说明土壤养分主要集中在表层,其中全氮、全磷、速效钾与土层深度呈显著负相关关系。本研究为喀斯特区坡地土壤格局及其成土过程积累了详细的野外调查数据,有关土层厚度空间格局及其养分随土深的变化规律能为该区生态服务功能提升、国土资源空间优化布局提供理论依据。

Grikes and cutters are common karst features in karst slopes which leading to high spatial heterogeneities of soil-rock structures.However,there is still lack of knowledge on spatial patterns of both soil types and related soil physical and chemical properties which in turn affected the rational planning and efficient use of limited water and soil resources in karst areas.In this study,12 trenches(perpendicular to contour lines with a length of 24 m and a width of 1 m)were dug from downslope to upslope direction in a karst slope.The trenches were divided into three groups namely shallow soil type,middle soil type,and deep soil type according to their soil-rock structure and soil thickness.A typical trench was selected from each groups to investigate the spatial patterns of both soil thickness distribution and the main soil nutrients.The results are as follows.Soil thickness in karst slopes showed a high spatial variability ranging from 0 to 430 cm with the variation coefficient between 12.0%and 85.3%.The soil fertility was generally low,and the comprehensive fertility coefficient gradually decreased with the increase of soil depth.The soil fertility level of the 0-10 cm depth was relatively high,in contrast to the extremely poor soil fertility level below 10 cm.It is indicated that the soil nutrients mainly concentrate at the surface soil layer.Among all of those soil fertility index,total nitrogen,total phosphorus,and available potassium were significantly negatively correlated with soil depth.This study accumulated detailed field survey data for deepening the knowledge of soil properties spatial patterns and soil formation processes in karst hillslopes.The results can provide a theoretical basis for the improvement of the ecological service function and the optimal layout of land resources in the karst area.