SEED DISPERSAL, GERMINATION AND SEEDLING GROWTH OF 6 HELOPHYTE SPECIES IN RELATION TO WATER-LEVEL ZONATION

1. Seed dispersal, germination, and seedling growth characteristics of six helophyte species, Iris pseudacorus, Phalaris arundinacea, Phragm ites australis, Typha angustifolia, T. latifolia and Scirpus lacustris , were investigated in relation to their water-level zonation. 2. The experiments demonstrated a large variation in these characteristics be tween the species. 3. Propagule floating capacities range from < 1h (S . lacustris) to > 1000 h (I. pseudacorus). 4. Seed germination in a wa ter-level gradient revealed two groups with respect to germination per centage - exposed soil species (I. pseudacorus, Phalaris arundinacea, Phragmites australis) and submerged soil species (T. angustifolia, T. latifolia). 5. There were two contrasting types of seedling growth res ponse to submergence and exposure: one group of species formed longest leaves under exposed conditions (Phalaris arundinacea, Phragmites aus tralis, I. pseudacorus), and the other under submerged conditions (S. lacustris, T. latifolia, T. angustifolia). 6. The results suggest that early life-history characteristics of the species relate to their loc ations in the riparian zonation: Phalaris arundinacea and Iris pseudac orus at the higher end, Phragmites australis intermediate, and Typha s pp. and Scirpus lacustris at the lower end. Species occurring at lower locations show adaptations to (periodical) flooding of the soil (subm ersed germination and growth), while those from higher locations requi re prolonged exposed soil conditions to germinate and to survive the e stablishment stage.