Structure and floristic composition of the Heard Island "Pool Complex" Community

The stratigraphy, hydrology and vegetation of the Heard Island (sub-Antarctic; 53 deg. 05'S, 73 deg. 30'E) 'pool complex' bogs are described. Spatial variation in processes that might have contributed to their formation are discussed. This community occurs where drainage has been impeded, with Callitriche antarctia being the indicator species. Particular attention is paid to the interaction of the vegetation, pools and animals. Surface stratigraphy, peat depth, water depth and vegetation composition were measured along transect lines. Species over abundance data of 300 quadrats were classified using a two-way indicator of species analysis program and ordinated using detrended correspondence analysis. The major factors determining vegetation composition were found to be peat depth, surface topography, and the degree and type of animal disturbance. Similarities between the pool complexes on Heard Island and bogs back in Tasmania, and northern hemisphere temperate and boreal zones appear to diminish as the density of the animals occupying this habitat increases.

本研究描述了赫德岛（亚南极；南纬53°05′，东经73°30′）“塘复合体”沼泽的地层学、水文特征与植被组成，并探讨了可能促成该类沼泽形成的各类过程的空间变异特征。该植被群落分布于排水受阻的生境中，以南极水马齿（Callitriche antarctia）为指示物种。研究重点关注了植被、塘体与动物之间的相互作用关系。研究人员沿样带测定了表层地层、泥炭厚度、水深及植被组成；针对300个样方的物种盖度-多度数据，采用双向指示种分析（two-way indicator species analysis）程序完成分类，并通过除趋势对应分析（detrended correspondence analysis）实现排序。研究发现，决定植被组成的主要影响因素包括泥炭厚度、表层地形以及动物干扰的程度与类型。随着栖息于该生境的动物种群密度升高，赫德岛塘复合体与塔斯马尼亚本土沼泽、北半球温带及寒带地带沼泽之间的群落相似性呈现逐渐减弱的趋势。