POLLEN REPRESENTATION OF FORESTED WETLAND PLANT COMMUNITIES, ATLANTIC COASTAL PLAIN RIVERS (USA)

We examine the relationship between source vegetation and pollen assemblages in Atlantic Coastal Plain forested wetlands by analyzing pollen deposited in surface sediments, annual accumulation on clay pads, and annual influx in pollen traps in transects along the Roanoke River in North Carolina and five rivers in the Chesapeake Bay watershed. These represent several types of forests including: levee or upland forests with short durations of flooding; seasonally flooded forests between levees and backswamps; and swamp forests with seasonal to permanent standing water. Pollen assemblages from levee or upland sites have the highest percentages of Carya, Ulmus, Fraxinus, Ilex, and other hardwood pollen, with relatively low abundance (<5%) of Liquidambar. In seasonally flooded forests, Liquidambar and Acer pollen are more abundant, and Taxodium, Nyssa, and hardwood pollen are present. Swamp forests with long hydroperiods have the highest proportions of Taxodium and Nyssa pollen.

Pollen assemblages from the surface centimeter of sediment and one year's accumulation on adjacent clay pads have very similar composition, indicating that surface sediment samples are representative of recent pollen accumulation. Comparison of clay pad and pollen trap data will clarify the relative roles of fluvial and atmospheric pollen transport in these forested wetland communities. Down-core and surface assemblages were compared statistically to reconstruct past hydroperiod and vegetational trends throughout the late Holocene; these results document the impact of Colonial land clearance and subsequent land-use changes on riparian vegetation in the Atlantic Coastal Plain of the United States.