Effect of sedimentation, hydrology, and light intensity on the emergence of seedlings in a Taxodium distichum swamp

The establishment of vegetation is dependent upon seeds arriving at locations that are favorable for germination or incorporation into the seed bank for later germination. Woody plant species in Taxodium distichum swamps have hydrochorous seed dispersal and this causes seeds to be deposited together. These co-occuring species are likely to compete with one another but different habitat requirements should therefore favor some species over others and thus allow for coexistance.; The seed bank of a T. distichum swamp was investigated under greenhouse conditions and in the field to determine the effects of flooding, sedimentation, and light intensity were examined to determine their effect on seedling emergence. Seeds of four woody plants that are dominant or common in T. distichum swamps in southern Illinois; Taxodium distichum L. (Rich), Nyssa aquatica L., Cephalanthus occidentalis L, and Gleditsia aquatica Marshall were also buried by sediment under different hydrologic and light conditions to examine differences in seedling emergence. Lastly, seed survivorship for the four species was determined for unburied and buried seeds under flooded conditions in the field.; Cephalanthus occidentalis, Cyperus erythrorhizos, and other herbaceous species were the most common species to emerge from the seed bank. Sedimentation and flooding reduced the number of seedlings and the number of species that emerged but each factor was only significant without the other. Flooding removed the most common species while enhancing the germination of less common species (e.g. Sagittaria calycina). The highest seedling emergence occurred at intermediate light intensities.; Sedimentation was the most important factor that effected seedling emergence of the four species studied. Sedimentation prevented the emergence of T. distichum seedlings, while C. occidentalis was only capable of emerging through 0.25 cm of sediment. Nyssa aquatica and G. aquatica were capable of emerging following burial by 2 cm of sediment but emergence was reduced. Taxodium distichum had the lowest seed survivorship followed by N. aquatica and G. aquatica, while C. occidentalis had the longest-lived seeds. Burial of seeds was not a significant factor in determining seed survivorship.