Variation in plant cover and flower production of Carex rostrata and C. vesicaria within a freshwater littoral zone. A 14-year time course.

Odland, Arvid

Aims: The main aim has been to quantify long-time variation in plant cover of Phalaris arundinacea, Carex rostrata and C. vesicaria, and number of Carex flowering shoots in plots situated along a littoral elevation gradient. Study area: The study area lies on the outer edge of a freshwater fluvial delta in the northern part of Myrkdalen Lake (229 m a.s.l.), W Norway (60°40' N, 6°28' E). The lake summer water level was in 1987 permanently lowered by 1.4 m exposing a stretch of ca. 40 m of the sediments. Methods: A transect was randomly selected on the exposed sediments perpendicular to the new shoreline, and continuous sample plots were permanently marked. Species percentage cover and number of Carex flowering shoots were counted in twenty-six 1 × 0.5 m plots and repeated 14 times from 1993 until 2020. The species data were related to variation in elevation, water level and temperature. Results: Plant percentage cover in the permanent study plots varied strongly during the investigation period. Relationships between species cover and the environmental variables were, however, not statistically significant. C. vesicaria and C. rostrata showed major variation in flower production both in relation to elevation and with time. C. vesicaria flower production increased significantly in years with elevated temperature and decreased in years with high water level. C. rostrata produced less flowers than C. vesicaria, except during the first study years. The variation in C. rostrata flower production was not significantly related to changes in water level or temperature, but the production increased with its cover and was reduced with increased P. arundinacea cover. Mean temperature and water level of the two last years explained the variation in mean number of flowering shoots best. Flower production of the two species varied in parallel with a significant correlation. Variation in species percentage cover was significantly related to C. rostrata flower production but not to C. vesicaria flower production.

FLOWERING of plants; REED canary grass; WATER levels; LITTORAL zone; TRANSECT method

Phytocoenologia, 2024, Vol 52, Issue 1, p43

0340-269X

Academic Journal

10.1127/phyto/2024/0414