喀斯特峰丛洼地不同植被类型土壤水分的空间异质性分析--以广西环江毛南族自治县西南峰丛洼地区为例

Spatial heterogeneity of soil moisture under different vegetation types in peak-cluster depression——A case study in southwest cluster peak depressions region of Maonan Autonmous County,Guangxi

通过网格(5 m×5 m)取样,用地统计学方法研究了喀斯特峰丛洼地4个典型植被类型表层土壤(0～10 cm)水分的空间导质特征,探讨了其生态学过程和机制。结果表明,随着干扰强度的降低,植被产生了由农作物(Ⅰ)→人工林(Ⅱ)→次生林(Ⅲ)→原生林(Ⅳ)的变化,土壤水分显著提高,空间变导特征明显不同,Ⅰ、Ⅱ、Ⅲ和Ⅳ分别符合指数模型、高斯模型、指数模型和球状模型,块金值与基台值之比(C_0/(C_0+C))在0.269～0.500之间,具有中等的空间相关性,Ⅰ和Ⅳ土壤水分的空间结构相似,(C_0/(C_0+C))值较大,随机因素和自相关异质性各占50%,分维数D值较大,空间依赖性较小,Ⅱ和Ⅳ相反;农业耕作区土壤水分的空间延续范围较大,变程达252.9 m,其他3个植被类型的变程均较小(141.2～163.2 m);Kriging等值线图从不同位置和方向上清楚地表明Ⅰ和Ⅳ土壤水分的空间分布均呈凸型分布,Ⅱ呈单峰分布,Ⅲ呈凹型分布;影响土壤水分空间分布的因子很多,其中干扰通过对植被的调控发挥了关键作用,降低干扰是喀斯特峰丛洼地脆弱生态系统水资源改善、合理利用及生态恢复重建的重要举措。

In this paper, the authors tries to illustrate the spatial heterogeneity of the soil moisture in surface layer （0-10 cm） under four typical vegetation types and the ecological processes and mechanism in peak- cluster depression. The results show that the soil moisture in surface layer increases significantly with the reduced disturbance gradient, and vegetation takes a succession change from crops （ I ） to man-made forest （ Ⅱ ）, to secondary forest （ Ⅲ ）, to primary forest （ Ⅳ ）. The spatial heterogeneity of the soil moisture in surface layer under the four vegetation types is diverse. Exponential, Gaussian, exponential and spherical models fit best for the spatial patterns of soil moisture in surface layer in I and Ⅲ , Ⅱ , and Ⅳ, respectively. The values of （Co/（Co0＋C）） ranged from 0. 269 to 0. 500, which indicates the soil moisture in the four types having medium spatial autocorrelation. The spatial patterns of the soil moisture in surface layer are similar in type I and Ⅳ, with relative large value of （Co/（Co-4-C）） and fractal, which suggests less dependence on spatial existed in the two vegetation types. The reverse is true to type Ⅱ and Ⅳ. The range in type I is up to 252.9 m, and the ranges of the other three vegetation types are relative small （from 141.2 to 163.2 m）. The Kriging contour maps clearly show the spatial distribution of the soil moisture in type I and Ⅳ is convex, while that in Ⅱ is unimodal and in Ⅲ concave. It is suggested that spatial pattern of the soil moisture in surface layer is affected by a large number of factors, among which disturbance plays a key role through regulating vegetation. Therefore, to reduce disturbance might be an important measure for the improvement of water resource and the restoration of eco-environment in karst peak-cluster depression.