THE PATTERNING OF PLANT-COMMUNITIES AND EDAPHIC FACTORS ALONG A HIGH ARCTIC COASTLINE - IMPLICATIONS FOR SUCCESSION

Isostatic rebound and the periodic development of ice-push beach ridge s have created topography suitable for development of biologically ric h polar eases along the northeast coast of Devon Island, Canada. Disti nct patterning of both plant communities and edaphic factors from coas tal shoreline areas inland indicate primary succession with a directio nal species replacement. At Rocky Point (emergent <2000 BP) biological development along the shore is initiated by marine algae that are inv aded by cyanobacteria. These organic mats are colonized by Puccinellia on the shoreline of these brackish lagoons. Where the topography grad es upslope, via concave areas, the toposequence from Puccinellia proce eds through Dupontia --> Carex --> Salix hummocks --> cushion plant-li chen communities. In drier, convex areas Puccinellia proceeds through rosette-herb hummocks --> cushion plant-lichen communities as a topose quence. Reduced levels of salinity and of nitrogen fixation upslope (f rom the shore) along with increased depth of organic soils and ability of soils to hold more soil water appear important in the conversion o f Puccinellia- to Dupontia- to Carex-dominated meadows. This is the ma jor chronosequence at Rocky Point and it is these Carex/meadows that o ccupy most of the wetlands of Truelove Lowland. The Salix hummocks and cushion plant-lichen communities: of all drier habitats resemble comm unities of similar species composition on the beach ridges of the lowl and.