The vegetational zonation of the East Pen Island salt marshes, Hudson Bay

Abstract

The extensive salt marshes at East Pen Island in Hudson Bay are described in quantitative terms and the well-marked sequence of species is characterized. The lower marsh is dominated by Puccinellia phryganodes and Carex subspathacea, with Hippurus vulgaris and Senecio congestus abundant in the salt pans. The midmarsh has well-developed swards of Dupontia fisheri and Celamagrostis neglecta, which give way to stands of Carex aquatilis in a well-developed freshwater marsh below the first beach ridge. The results are compared with other arctic salt marshes, and the development of a wide freshwater marsh in the upper zone of the salt marsh is described. This feature is perhaps unique to the Hudson Bay marshes and is a function of meltwater runoff from the surface of the permafrost table. This results in the high, standing water table at the top of the marsh, which is maintained by the permafrost table of the salt marsh itself.A transit survey of the marsh relates the quadrat samples to a high-tide datum point and allows interpretation of the vegetation sequence in terms of saltwater inundation. The depth of the active layer of the salt marsh is also described.