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Influences on the Distribution of Carex Exilis: An Experimental Approach

Santelmann, Mary V.
Ecology 1991 v.72 no.6 pp. 2025-2037
Carex, Sphagnum, acidity, bogs, coasts, ecotypes, fens, germination, greenhouse experimentation, mosses and liverworts, nutrient availability, peat, reproduction, salinity, seedlings, water table
Carex exilis occurs in bogs and fens along the Atlantic coast, but only in fens in the midcontinent. I experimentally tested five hypotheses explaining this pattern. Reciprocal transplants were made, and no differences were found among populations, implying that there are no bog—adapted ecotypes. Instead, C. exilis growth and reproduction depended most on conditions under which plants were grown. Plants from all populations studied could complete their life cycle in coastal bogs, coastal fens, and midcontinental fens, but not in midcondinental bogs. Greenhouse experiments showed that salinity and acidity had no significant effect on germination and growth; increased nutrient supply and water table level did. Seedlings of C. exilis grew vigorously on peat from a midcontinental bog when the water table was kept artificially near the moss surface, but most died when the water table was at its natural level, 20 cm or more below the moss surface. The water table of coastal bogs is normally high. Water level affected competition for light between Sphagnum moss and C. exilis seedlings. Under the drier conditions of midcontinental bogs, Sphagnum overgrew the seedlings; under wetter conditions typical of coastal bogs, seedlings grew faster than Sphagnum, and coexisted with the moss.