The biology of the annual Salicornia europaea agg. at the limits of its range in Hudson Bay.

The biology of a marginal population of the annual Salicornia europaea agg. has been examined at La Pérouse Bay, Manitoba, on the shores of Hudson Bay. Plants were confined to south-facing sites which became hypersaline in summer, but which were not covered by tides. The difference in temperature of surface sediments between south- and north-facing slopes was as much as 7°C. Although most seedlings emerged in June, germination continued throughout the summer, but plants that appeared late in the season failed to set seed. Mortality of both seedlings and adult plants was low. Seeds or seedlings from a south-facing slope were transplanted during a 2-year period within the same site, into another south-facing site, to a north-facing site, and to an intertidal site. Germination either failed to occur or else was poor at the latter two sites. In addition, seed production of mature plants was low compared with that for individuals transplanted within south-facing sites. Additions of nitrogen to north-facing slopes increased overall seed output per plant, but the ratio of unripened to ripened seeds remained the same as that in plants from untreated plots. The results are discussed in relation to the ecology of marginal populations.