Mosaics of vegetation and soil salinity: a consequence of goose foraging in an arctic salt marsh

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Abstract
Grubbing of roots and rhizomes of salt-marsh graminoids by lesser snow geese at La Pérouse Bay, Manitoba, on the Hudson Bay coast, has resulted in a vegetational mosaic. Bare sites, devoid of vegetation, occur adjacent to intact swards (high biomass sites). At some sites destruction of swards is incomplete (low biomass sites). In 1991 and 1992, highest soil salinities occurred in midsummer; surface sediments were flushed of salts by meltwater in spring and by tides in autumn. By late July, in both years, the soil was hypersaline in low biomass and bare sites, unlike that in the high biomass sites. The highest soil salinities were recorded in bare sites, especially in large bare patches. Aboveground plant biomass (g∙m−2) was a much better predictor of the salinity of soil water than the water content or redox potential of soil. Evaporative loss of water from tubes buried in sediments was higher in bare sites compared with that in vegetated sites. Differences in evaporation between sites led to large differences in the salinity of soil water but only small differences in soil water content. The upward movement of salts from buried Tyrell Sea sediments appears responsible for the development of hypersaline conditions. Key words: grubbing, goose grazing, plant biomass, sodium, soil water, hypersalinity.