Throughout the northeastern United States, inland non-tidal wetlands border highways and construction projects but there is little information on factors that affect their vegetation regeneration and diversity. A 4-year study compared two hydrologically-connected wetlands, located on each side of a state highway, in terms of their vegetation structure, soil seed bank composition and effect of flooding on seasonal regeneration response. Soil samples were collected in late-March and again in late-October of 1998-2001, from ten plots per transect in sunny and shaded vegetation margins of each pond. Each sample was divided in half, and kept saturated or consistently flooded in the greenhouse to allow for seed germination and species identification. To compare the species composition of the soil seed bank to that of the standing vegetation, species diversity and relative abundance were surveyed in mid-summer in plots adjacent to the randomly located soil sampling plots. At each pond, the vegetation margin consisted of a mosaic of species scattered in small patches over sunny and shaded sections. At both ponds, flooded soil samples had lower species diversity and seedling emergence than saturated samples, particularly in soil from less accessible shaded sites. Most species emerging from the soil seed bank were not found in adjacent vegetation survey plots, but soil and standing vegetation had similarly high plant species diversity. Although more seedlings emerged from Spring soil samples, Spring and Autumn soil samples had many of the same plant species emerging, primarily perennials in one wetland but 50 % annuals in the beaver-disturbed site. At both wetlands, annual differences in rainfall, seasonal variation in flooding, spatial variation in light availability and accessibility to external seed sources combined to affect the diversity of seeds in the soil seed bank. Historical differences between wetlands in disturbance from human construction and beaver activity may have affected also the rate of succession.

Key words: beaver disturbance, flooding, Phalaris arundinacea, soil seed bank, spring and autumn germination, urban wetlands