Postglacial history of a marl fen: vegetational stability at Byron-Bergen Swamp, New York

Byron-Bergen Swamp, an 800-ha mire complex in western New York, is a mosaic of hardwood–conifer forest, white cedar swamp, and open nonforested fens dominated by sedges, other herbs, and shrubs. The mire is a sloping, spring-fed rich fen in which marl deposition occurs in the open fens but not under forest. Two cores, 120 m apart, one in a marl fen and the other in a hardwood–conifer swamp, were taken to investigate the history of the mire. Sediment, pollen stratigraphy, and 14C chronology show that the Holocene record of local vegetation at each coring site was very different. One site was first a shallow marl pool (10 700 – 5600 years BP), then an open shrub–conifer vegetation, and finally a closed hardwood–conifer swamp. The other site progressed from a pine–spruce–tamarack swamp (10 700 – 8000 years BP) to a white cedar swamp (7500–3500 years BP) and then to a marl sedge fen (3500 years BP – present). The spatial arrangement of swamp forest and marl fen changed through time, responding to marl accumulation and lateral shifts in drainage pathways. Marl deposition occurred continuously at each site, although at different times, for several thousand years. The pattern of vegetation change that we found is not congruent with that predicted from classical hydrarch succession.Key words: marl, mire development, pollen stratigraphy, rich fen.

14,000 Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southeastern Massachusetts

Data from a transect of four cores collected in the Makepeace Cedar Swamp, near Carver, Massachusetts, record past changes in deposition, vegetation, and water level. Time series of palynological data provide a 14,000-yr record of regional and local vegetation development, a means for biostratigraphic correlation and dating, and information about changes in water level. Differences in records among cores in the basin show that water level decreased at least 1.5 m between ∼10,800 and 9700 cal yr B.P., after which sediment accumulation was slow and intermittent across the basin for about 1700 yr. Between 8000 and 5600 cal yr B.P., water level rose ∼2.0 m, after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 ± 200 cal yr B.P. Dry conditions may have continued after this time, but by 3200 cal yr B.P., the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level, where it is today. Peat has accumulated across the whole basin since 3200 cal yr B.P. Data from Makepeace and the Pequot Cedar Swamp, near Ledyard, Connecticut, indicate an early Holocene dry interval in southern New England that began 11,500 yr ago near the end of the Younger Dryas interval. The dry conditions prevailed between 10,800 and 8000 cal yr B.P. and coincide with the arrival and later rise to dominance of white pine trees (Pinus strobus) both regionally and near the basins. Our results indicate a climatic cause for the “pine period” in New England.