Seed dormancy in Carex canescens: Regional differences and ecological consequences

We compared the germination of seeds of Carex canescens from populations in four regions: northern and southern Sweden, and northern and southern Germany. Germination behaviour was expected to differ between regions owing to adaptations to the local climates. We compared three or four populations from each region in 31 germination experiments (different pre-treatments, different temperature regimes, light vs darkness). In a parallel experiment, we recorded seedling emergence under outdoor conditions from seeds sown in the late summer in northern Germany. Although there were differences in the level of dormancy between the 13 populations and four regions, we were unable to detect geographic patterns which could be explained in terms of differential adaptation to the local climates. Our data did not support a proposed hypothesis that populations experiencing more severe winter conditions would require a longer cold-stratification period. We compared the results from the outdoor experiment with germination data from the laboratory experiments. The latter could not be used to predict differences in the timing of seedling emergence, the time-span during which seedlings emerged, or the number of seedlings emerging. We conclude that the relevance of detected differences in dormancy level among species or populations must be interpreted with great care. First, the detection of geographical patterns requires extensive sampling, second, the ecological consequences of such differences should be established.