Woody plant species in bald cypress swamps are recruitment limited. Seeds of most wetland plants will not germinate under water and so must survive until draw down. Therefore, seed survivorship is a crucial component for natural regeneration of these forests. A field study was conducted to examine seed survivorship of four woody plant species common in bald cypress swamps in southern Illinois. Seeds of bald cypress (Taxodium distichum), water tupelo (Nyssa aquatica), water locust (Gleditsia aquatica) and buttonbush (Cephalanthus occidentalis) were placed under flooded conditions in situ over 18 months. Considerable variation was observed in initial seed viability among the four species. There were significant declines in seed viability of all four species. Rates and patterns of seed survivorship differed among the four species. Bald cypress had the fastest decline in seed survivorship with only one half of seeds surviving 1.4 months, followed by water locust (14 months). One half of water tupelo and buttonbush seeds were predicted to survive 20 and 39 months, respectively. Bald cypress seeds had an exponential decline in viability over time, where as water tupelo and water locust seeds declined according to a second order regression line and seeds of buttonbush declined linearly over the duration of the study. Estimated maximum age of seeds was similar between water tupelo (30 months), bald cypress (25 months) and water locust (23 months). Buttonbush had the longest estimated seed longevity (150 months). These differences in seed survivorship may have significant effects on community structure by all but eliminating bald cypress seedling establishment following drawdown while favoring the establishment of buttonbush. Infrequent drawdown events are also likely to greatly favor the establishment of buttonbush over other species due to seed longevity.

Key words: Cephalanthus occidentalis, Gleditsia aquatica, Nyssa aquatica , Seed survivorship, Taxodium distichum