HR: 1400h
AN: PP43C-01    [Abstracts]
TI: Lake-Sediment Evidence for Variation in Mid-Holocene Climate and Vegetation in Western Massachusetts
AU: * Truebe, S A
EM: struebe@pangea.stanford.edu
AF: Earth Systems Program, Stanford University, 397 Panama Mall Mitchell Building 138 Mail Code 2210, Stanford, CA 94305, United States
AU: Oswald, W W
EM: woswald@fas.harvard.edu
AF: Department of Communication Sciences and Disorders, Emerson College, 216 Tremont Street, Boston, MA 02116, United States
AU: Foster, D R
EM: drfoster@fas.harvard.edu
AF: Harvard Forest, Harvard University, 324 North Main Street, Petersham, MA 01366, United States
AU: Doughty, E
EM: doughty@fas.harvard.edu
AF: Harvard Forest, Harvard University, 324 North Main Street, Petersham, MA 01366, United States
AB: A growing body of evidence indicates that significant, worldwide variations in climate occurred during the middle Holocene. Awareness of mid-Holocene climate change in eastern North America has implications for interpreting the vegetation history of the region. The range-wide decline of eastern hemlock (Tsuga canadensis) at 5400 cal yr BP has been interpreted by many as a pest or pathogen attack, though recent evidence attributes the event to an abrupt change in climate. A new sediment record from the Berkshire Hills of western Massachusetts, a region of historically high hemlock abundance, helps to address questions relating to the Holocene environmental and ecological history of eastern North America. Analysis of fossil pollen yields a record of changes in vegetation, while down-core variations in organic content (loss-on-ignition; LOI) serves as a proxy for changes in water depth and subsequently climate. Hemlock first arrived at Benson Pond 11,000 cal yr BP, when it abruptly increased in abundance. Hemlock abundance was relatively high between 9000 and 6600 cal yr BP, though there was some variability, relatively low from 6600 cal yr BP to 5900 cal yr BP, and then very high from 5900 until the abrupt decline at 5400 cal yr BP. Abundance remained low until 3700 cal yr BP. Variations in LOI indicate that the 6600 and 5400 cal yr BP declines in hemlock may have been associated with dry climatic conditions. Intervals interpreted as being relatively dry include 13,000-11,600 cal yr BP (the Younger Dryas event), 9500-9000 cal yr BP, 8500-8300 cal yr BP (perhaps representing the 8200 cal yr BP event), 6600-6000 cal yr BP, 5400-4700 cal yr BP, and 3900-3700 cal yr BP. Increased abundance of aquatic taxa during some of these intervals provides further evidence for lower lake levels, in particular during the hemlock decline beginning at 5400 cal yr BP. These data suggest climatic control of eastern hemlock abundance throughout the Holocene, but further research on high-resolution records is needed to better understand the role of short-term, abrupt climatic variability on the vegetation history of eastern North America.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1637 Regional climate change
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly