Species patterns, edaphic characteristics, and plant water potential in a high-arctic brackish marsh

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Abstract
Coastal brackish and salt marshes in the High Arctic are very limited floristically and in areal extent. Small marshes located on the northeast coast of Devon Island are dominated by distinct zones of Puccinellia phryganodes nearest the sea with Carex ursina, C. stans, Dupontia fisheri, and Alopecurus alpinus dominated zones landward. Soil salinity and chloride ion content increase seaward, but plant water potential becomes less negative, opposite to the expected pattern. Fresh water from the melting pack ice forms a lens over the more dense seawater below it. This meltwater dilutes the salts in the upper soil layer, creating a low salinity condition for the plants that inhabit the zones nearest the sea. We hypothesize that it is this "fresh" water that comes into contact with the roots of Puccinellia and Carex ursina, and thus, less-negative water potentials are maintained in these species. Although plant zonation can be explained in part by such considerations, we conclude that edaphic characteristics are not the only factors involved. A number of hypotheses are entertained.