SEED PRODUCTION GERMINATION RATE, AND SEEDLING ESTABLISHMENT OF SCIRPUS PUNGENS IN TIDAL BRACKISH MARSHES

We examined three components of sexual reproduction in Scirpus pungens in order to explain the scarcity of seedlings in tidal brackish marshes of the St.Lawrence River estuary in Quebec. Six transects were established in three plant communities within two marshes. Seed production varied between 1 and 621/m(2) among transects and increased with shoot density and the proportion of shoots with flowers. The number of seeds per fertile shoot did not vary among communities and averaged 1.8 +/- 0.1 (SE). The variation in seed production was related to the interacting effects of goose herbivory, soil type, and vegetative growth. The seed bank yielded 20-200 seedlings/m(2) at different sites. Germination rates obtained in situ under experimental conditions averaged 28% overall and reached 62% in one community with sandy substrate. Both the collection and seeding sites affected levels of germination. Seedlings varied between 0 and 25/m(2) among sites and represented 0-3% of the total number of shoots. Low seedling survival was attributed to sediment accretion. Seedlings established themselves successfully only on bare patches created by erosion of the micro-bluff separating the lower and the upper marsh. We conclude that seeding of S. pungens is not an effective technique to create or restore tidal marshes where sediment accretion is important.