基于等面积高度带划分的贺兰山维管植物物种丰富度的海拔分布格局

Altitudinal pattern of vascular plant species richness based on equal-area belts in Mt. Helan

山地植物物种丰富度海拔分布格局是生物多样性研究的热点之一。以往研究中一般将山体划分为等海拔间距的高度带,以分析物种丰富度的垂直格局,其缺陷在于因各高度带面积不相等而可比性下降。为消除面积不相等的影响,作者利用数字高程数据(DEM,Digital Elevation Model)在地理信息系统(GIS)工具支持下,尝试将贺兰山(海拔范围1,300-3,500m)划分为等面积的数个高度带,从而分析其物种丰富度的海拔格局。结果表明:(1)贺兰山物种丰富度呈现为单峰式海拔格局,峰值出现在海拔2,000m附近。(2)逐步回归分析显示,坡度异质性是解释物种丰富度海拔分布格局的最优因子。高度带的坡度异质性越大,意味着地形的起伏变化越大,反映出生境类型越趋多样化,从而可维持多个物种的共存。(3)贺兰山植物物种丰富度在海拔2,000m附近达到峰值,可能与植被演变历史、气候条件、地形复杂度、生态过渡带和中间膨胀效应的共同影响有关。(4)对山体进行等面积划带,可直接消除面积不相等带来的影响,与等间距划带的方法相比,尤其在物种海拔分布信息准确度较高时更具优势。

Altitudinal pattern of plant species richness along an elevational gradient has often been studied by dividing the mountains into equal-elevation belts. However, comparisons of species richness among different belts with different areas is not appropriate. Based on a Digital Elevation Model （DEM） and Geographic Informational System （GIS）, we divided Mr. Helan （1,300-3,500 m） into several equal-area belts along an altitudinal gradient, and compared the plant species richness among them. The results were as followed： （1） The altitudinal pattern of species richness in Mt. Helan showed a unimodal shape, peaking around 2,000 m altitude. （2） The slope heterogeneity was the primary variable to explain the altitudinal pattern of species richness. High values of slope heterogeneity could reflect the complex topographic features and diversified habitats within a belt, implying a favorable condition for more species to coexist. （3） The unimodal pattern of species richness might result from a combined effect of evolutionary history of vegetation, climates, topographic features, ecotone, and the mid-domain effect. （4） Compared with equal-elevation belts, equal-area belts could directly eliminate the influence of area upon species richness, leading to a more reliable analytic result, especially when the species data were accurate at all altitudinal ranges .