生态交错带的定量判定

Quantitative Methodologies for Ecotone Determination

生态过渡性是梯度环境的特征之一 ,过渡带的显著性是地理学和地植物学中长期争论的重要问题 ,生态交错带位置和宽度的判定是定量研究交错带生态学过程的基础。样带法是采集非连续梯度数据和研究交错带的结构、功能和格局梯度变化的有效方法。生态交错带变化最为显著的特征是植被的变化 ,包括植物种类组成和植被结构的变化 ,植被生态学群落分析中的相异系数、β多样性、梯度分析和分类排序技术等已被证明是成熟可靠的方法。介绍两种交错带定量判定的有效方法。游动分割窗技术是通过滑动求取样带上样点间相异系数 ,通过相异系数变化曲线判定交错带的位置和宽度。分割窗技术提供了敏感地定位非连续梯度的客观且有效的方法 ,它不仅可用于环境梯度上的等距离样点取样 ,而且可用于非等距离梯度样带多元变量的分析。植被的特征是对生态环境连续体的综合反应 ,植被在环境梯度上的排序参数提供了一种较好的交错带定量指标 ,样带植被数据特征参数的变异轮廓图能够反应植被沿样带的物种组成、结构和空间变化格局 ,可以反应植被沿环境梯度的 β多样性和植物群落的梯度分化 ,植被变异侧面轮廓图的间断或不连续 (突变 )区间就是群落边界的位置。

Ecotone is one of the important features of environmental gradient. Where there is an apparent ecotone along a gradient is a controversy existed in geography and geobotany. However, quantitative determination of its location and width is the basis for studying the ecological process of the ecotone. Transect is an effective methodology to collect non-continual gradient data and to study the structure, function and pattern variation of the ecotones. The most important characteristic of the ecotone is the variation of vegetation, including species composition and community structure. Community methodologies, such as dissimilarity coefficient, β diversity, gradient analysis and vegetation classification and ordination, in vegetation ecology have been demonstrated reliable in ecotone determination. This paper introduces two new methods to quantitatively determine ecotone. Moving split-window technique is a method to calculate dissimilarity coefficients between split windows by moving sampling unit from one end to the other. And then judge the location and widths of ecotone from the curve of dissimilarity coefficients along transect. Moving split-window technique is an objective and effective method to locate non-continual gradients along transect. It is not only suitable for sampling in equidistant plot, but also for multi-variable analysis in non-equidistant plots along the transect. The characteristics of vegetation are comprehensive response of environmental continuum. Of course, the ordination parameters along environmental gradient are appropriate indicators for determining ecotone. Therefore, vegetation differential profile of ordination parameters can reflect the spatial patterns of species composition and vegetation structure along transect. It can be good indicator of β diversity and gradient differentiation along the environments. The disconnected or non-continual areas of vegetation differential profile are location of ecotone.