PALEOECOLOGY OF EASTERN NEW YORK’S RENSSELAER PLATEAU AND IMPLICATIONS FOR LATE PLEISTOCENE AND HOLOCENE CLIMATE CHANGE

Sediment cores from Dyken and Shaver Ponds on the Rensselaer Plateau of eastern New York state were analyzed for sediment chemistry, pollen, plant macrofossils, and diatoms to reconstruct the vegetation and climate history since Laurentide ice sheet retreat of this previously unstudied region. The Plateau hosts a diverse assemblage of ecological communities, including hemlock-northern hardwood forest, beech-maple mesic forest, appalachian oak-pine forest, maple-basswood rich mesic forest, and spruce-northern hardwood forest, among others, allowing for a sensitive response to variations in temperature and precipitation over time. Furthermore, the Plateau lies near the boundary between two climatic regimes that show different histories over the Holocene. Both cores record many of the classical features of pollen records throughout the Northeast, including expansion of Alnus during Younger Dryas cooling, followed by a Pinus maximum that indicates the onset of Holocene warming. Both also show the classical mid-Holocene hemlock decline that has been widely attributed to drought, though neither contain other indicators of drying. Dyken Pond shows a sharp decline in organic carbon content and increase in Najas seeds close to the time of the 9.2 ka event, which may signify drier conditions at that time. Shaver Pond shows a similar decline in LOI. Reappearance of Abies and Picea pollen along with Larix needles toward the top of both cores is consistent with a return to cooler conditions at the end of the Holocene.

The diatom flora of both ponds are typical of low-alkalinity waterbodies throughout the Northeast and seem to reflect late glacial to early Holocene watershed acidification followed by additional pulses of acidity associated with variations in the abundance of Tsuga. Discostella stelligera is a prominent taxon in both records. At Shaver Pond it is found throughout the nearly 10,000-yr-long record, but at Dyken Pond it is largely restricted to the early Holocene. In addition to this taxon, Lindavia and Melosira species dominate the record at Shaver Pond whereas Aulacoseira species are abundant at Dyken Pond, likely reflecting differences in nutrient inputs to both ponds. Both the pollen and diatom records from the Rensselaer Plateau suggest wetter conditions during the Holocene than in New England.