MOSAICS OF VEGETATION AND SOIL-SALINITY - A CONSEQUENCE OF GOOSE FORAGING IN AN ARCTIC SALT-MARSH

Grubbing of roots and rhizomes of salt-marsh graminoids by lesser snow geese at La Perouse Bay, Manitoba, on the Hudson Bay coast, has resul ted in a vegetational mosaic. Bare sites, devoid of vegetation, occur adjacent to intact swards (high biomass sites). At some sites destruct ion of swards is incomplete (low biomass sites). In 1991 and 1992, hig hest soil salinities occurred in midsummer; surface sediments were flu shed of salts by meltwater in spring and by tides in autumn. By late J uly, in both years, the soil was hypersaline in low biomass and bare s ites, unlike that in the high biomass sites. The highest soil saliniti es were recorded in bare sites, especially in large bare patches. Abov eground plant biomass (g.m(-2)) was a much better predictor of the sal inity of soil water than the water content or redox potential of soil. Evaporative loss of water from tubes buried in sediments was higher i n bare sites compared with that in vegetated sites. Differences in eva poration between sites led to large differences in the salinity of soi l water but only small differences in soil water content. The upward m ovement of salts from buried Tyrell Sea sediments appears responsible for the development of hypersaline conditions.