Distribution and variation in growth of Scirpus maritimus var. paludosus on the Canadian prairies

Abstract

Scirpus maritimus var. paludosus occurs in saline lakes in the prairie and parkland regions of Alberta, Saskatchewan, and Manitoba. Its distribution within wetlands is dependent upon the degree of salinity during germination and seedling establishment. In hypersaline wetlands, S. maritimus is found only on a narrow band on the upper slope of the basin; as these wetlands become dry, only the upper slope has mud flat salinities low enough to allow successful germination. In wetlands of the saline category, S. maritimus occurs over a broad area of the upper and middle slope, and in moderately saline wetlands it is usually outcompeted by freshwater species but may dominate the centre of the basin in low-water years. Canonical-correlation analysis of S. maritimus growth variables in 24 sites in Saskatchewan, Manitoba, and Alberta showed a large phenotypic growth response to different environmental conditions. On dry and highly saline sites, S. maritimus tubers developed short, and in most cases nonflowering, stems. In shallow water and reduced salinity, individual stems were larger and stem density and above-and below-ground biomass were at a maximum. In water greater than 40 cm deep and with low salinities, individual stems and inflorescences reached maximum size, but the much lower stem density resulted in reduced total biomass. Seed production was also influenced by the previous year's water levels. At those sites which were dry and then flooded the next year, more stems flowered and inflorescences were larger than at sites which had been flooded continuously the previous year.