干旱区生态环境知识资源中心

Isostatic rebound and the periodic development of ice-push beach ridges have created topography suitable for development of biologically rich polar eases along the northeast coast of Devon Island, Canada. Distinct patterning of both plant communities and edaphic factors from coastal shoreline areas inland indicate primary succession with a directional species replacement. At Rocky Point (emergent <2000 BP) biological development along the shore is initiated by marine algae that are invaded by cyanobacteria. These organic mats are colonized by Puccinellia on the shoreline of these brackish lagoons. Where the topography grades upslope, via concave areas, the toposequence from Puccinellia proceeds through Dupontia --> Carex --> Salix hummocks --> cushion plant-lichen communities. In drier, convex areas Puccinellia proceeds through rosette-herb hummocks --> cushion plant-lichen communities as a toposequence. Reduced levels of salinity and of nitrogen fixation upslope (from the shore) along with increased depth of organic soils and ability of soils to hold more soil water appear important in the conversion of Puccinellia- to Dupontia- to Carex-dominated meadows. This is the major chronosequence at Rocky Point and it is these Carex/meadows that occupy most of the wetlands of Truelove Lowland. The Salix hummocks and cushion plant-lichen communities: of all drier habitats resemble communities of similar species composition on the beach ridges of the lowland.