Paper No. 5
Presentation Time: 2:55 PM
ENVIRONMENTAL CHANGES OF THE MID- HUDSON ESTUARY IN THE LAST MILLENNIAL
The Hudson River serves many significant roles in the regional environment. It is important to understand how humans and climate have changed the ecosystems within such an important estuary. We use multiple proxies, including microfossils, to study the paleoecology and paleoclimate of two fresh tidal marshes -Tivoli North Bay (42º 02′N, 73º 55′W) and Stockport Flats (41º 19′N, 73º 47′W). These wetlands are two of four Hudson River National Estuarine Research Reserve (HRNERR) sites. Pollen, spores, macrofossils, charcoal, organic matter content, and radiometric chronologies at these sites reveal significant vegetation changes which reflect local and regional ecological and landscape alternation due to anthropogenic and climatic changes over the last 1000 years. European settlements are marked by a very abrupt shift in vegetation and sediment composition as a result of deforestation, invasive species introduction, land clearance, and infrastructure construction. Our data indicate that land use changes after European settlement significantly affected sedimentation patterns, resulting in the alteration of wetland hydrology and vegetative composition. At Tivoli, higher inorganic input appears to contribute to marsh composition changes from wetland herbaceous species to woody taxa throughout the most recent centuries. The structure of the upland forest slightly changed through time. After the 17th century, Betula dominates the forest in addition to Quercus and Pinus. Weedy and invasive species including Typha, Phragmites australis, Ambrosia, Lythrum salicaria, Impatiens, Chenopodiaceae and Gramineae drastically expand, replacing native ferns and sedges as human impact increases at both sites. At Stockport Flats, the area was not a marsh prior to the European settlement based on pollen, seeds, and LOI. At Tivoli, microscopic charcoal increases reflects drought during the Medieval Warm Interval which is recorded at other sites in the Northeast. We will present our data and discuss the relationship among human activities, ecosystem changes, and sedimentation pattern changes based on these microfossil records in comparison with other proxies.