ABSTRACT

We investigated the influence of 6 morphometric and geographic factors on the structure and composition of plant communities in 56 temporary freshwater rockpools from 7 pool landscapes in the Maltese Islands. The factors considered were water depth, sediment depth, surface area, shading, distance from the coast, and elevation above sea level. Coverage data for 30 plant taxa in 3 functional forms (aquatic, amphibious, and terrestrial) were collected during one hydrological cycle. The relationships between pool morphometry, pool location, and community composition were tested using multivariate analyses. The contribution of spatial variables to variation in community composition across pools was examined using principal coordinate analysis of neighbour matrices (PCNM). The results suggested that pool morphometry varied both within and across landscapes, reflected in similar differences in community composition. Moreover, 47.6% of the explained community variation in the whole dataset was contributed exclusively by space predictors, suggesting that pool “location” is an important determinant of community composition. The morphometric property that exerted the highest influence on the dominance of a given plant functional form was the pool surface area, with greater surface areas promoting the presence of amphibious species relative to obligate hydrophytes. Conversely, the presence of specific species was mainly controlled by water depth and sediment depth. The most influential predictors of community composition varied across landscape, suggesting that pool location can be an important determinant of community structure and composition, and pool morphometry would favour certain functional forms and species over others.

摘要

我们调查了6个形态和地理因素对来自马耳他群岛7个水池景观的56个临时淡水岩池中植物群落的结构和组成的影响。考虑的因素包括水深，沉积物深度，表面积，阴影，距海岸的距离以及海拔高度。在一个水文循环中，以三种功能形式（水生，两栖和陆地）收集了30种植物类群的覆盖率数据。使用多元分析测试了池形态，池位置和社区组成之间的关系。使用邻域矩阵的主坐标分析（PCNM）检验了空间变量对各池群落组成变化的贡献。结果表明，池内景观形态在景观内和景观间均发生变化，反映出社区组成的相似差异。此外，整个数据集中解释的群落变异的47.6％仅由空间预测因子贡献，这表明池的“位置”是群落组成的重要决定因素。对给定植物功能形式的控制力影响最大的形态学性质是库表面积，与专性水生植物相比，更大的表面积促进了两栖物种的存在。相反，特定物种的存在主要受水深和沉积物深度控制。最具影响力的社区构成预测因素因地域而异，