Plant Zonation in an Alaskan Salt Marsh: II. An Experimental Study of the Role of Edaphic Conditions

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Abstract
Field experiments were conducted to examine the response of mature plants to different edaphic conditions in a subarctic salt marsh. Five dominant perennial vascular species characteristic of distinct zones within the marsh were studied. The specific effects of salinity, waterlogging and soil type were determined. Results from a 2 yr reciprocal transplant experiment demonstrated that Carex lyngbyei, C. ramenskii and Poa eminens (species characteristic of less saline sites) were inhibited in the outer mudflat zone, where soil water salinity was highest (up to 35.permill.). The above-ground biomass of Puccinellia nutkaensis, a dominant species on the outer mudflat, was 3-4 times greater at more inland, drained sites; this species usually died in the waterlogged inner sedge marsh. Triglochin maritimum from the inner mudflat grew well in all sites to which it was transplanted. When cultured for 8 wk in pots of either peat or silt, all species grew best in the least saline (3.permill.) waterlogged treatment. The growth of P. nutkaensis was greatly inhibited in peat: fertilization (N, P and K) overcame the inhibition. The relative salt tolerance of each species corresponded with the soil salinity in its zone of occurrence, and may determine its seaward limit of distribution within the marsh. Where potential distributions overlap, as at most moderate and low salinity sites, biotic factors such as between-species competition may be more important in maintaining the observed zonation patterns. P. nutkaensis, in particular, appears to be restricted to the outer mudflat because it is a poor competitor in the inner mudflat and riverbank level zones.