Holocene Development of a Forested Wetland in Central Massachusetts

• Investigators: David Foster, Tad Zebryk
• Contact: David Foster
• Start date: 12500 BP
• End date: present
• Location: Prospect Hill Tract (Harvard Forest)
• Latitude: +42.539330
• Longitude: -72.179720
• Elevation: 355 meters
• Taxa: Acer rubrum (red maple), Acer saccharum (sugar maple), Betula (birch), Castanea (chestnut), Fraxinus (ash), Nyssa (black gum), Picea (spruce), Pinus (pine), Populus (aspen), Quercus (oak), Tsuga canadensis (hemlock)
• Keywords: disturbance, fire, forest history, pollen analysis, vegetation dynamics
• Release date: 2003
• EML version: knb-lter-hfr.100.2
• Revisions:
• Abstract:

  The post-glacial history of two adjacent sites in the Harvard Forest, a 10-ha swamp (Black Gum Swamp) and a 0.006-ha hollow (Hemlock Hollow) in a Tsuga canadensis forest were investigated using pollen analysis. The sites were selected in order to contrast the regional vegetation history revealed from the swamp sediments with the local history of the Tsuga forest reconstructed from the Hollow sediments. Specific objectives were (1) to document the natural and anthropogenic disturbance history, (2) to examine the long-term vegetation dynamics of the two sites resulting from environmental change, species migration, and disturbance, especially with respect to Tsuga, and (3) to contrast the pre-and post-settlement vegetation and environments. The Swamp and Hollow cores contain continuous sediment records covering the past 12,300 and 9500 yr, respectively. Regional vegetation changes are delimited in six pollen zones: I, Herb zone, (12500 – 11800 yr BP); II, Picea zone (11800 –9350 yr BP) III, Pinus-Quercus zone (9350-8350 yr BP); IV, Tsuga-northern hardwoods zone (8350-1750 yr BP); V, Tsuga-Castanea-hardwoods zone (1750-200 yr BP); and VI, Post-settlement zone (200 yr BP-present). No disturbances are detected in the periods of tundra or boreal vegetation from 12500 to 8350 yr BP. Since 8350 yr BP three distinct disturbance processes are detectable: (1) fires recorded in discrete charcoal horizons, (2) the apparent pathogenic decline of Tsuga (4700-3500 yr BP) and the blight of Castanea (~1915 A.D.), and (3) post-settlement forest cutting, burning, land clearance an cultivation (1750 A.D. to present).

• Methods:

  Morphometric maps of the sites were constructed by probing with thin steel rods across a 25-m grid at Black Gum Swamp (BGS) and 1-m grid at Hemlock Hollow (HH). A total of 500 cm of sediment core length was obtained with a 5 cm diameter Russian corer from the deepest part of the BGS basin, and 72 cm of sediment was recovered at HH with a piston corer.

  Cores were sub-sampled volumetrically for pollen and charcoal analysis at measured stratigraphic intervals, spiked with eucalyptus-glycerin solution and processed using the method of Faegri and Iverson (1975). A minimum of 300 arboreal grains was identified at each level. Charcoal (greater than 15 μm longest dimension) was tallied for the entire core at BGS and the last 3000 yr at HH using the point-intercept method (Clark 1982). Organic carbon content was determined by loss-on-ignition at 550° C at 10-cm intervals at BGS and 1-cm intervals at HH (Dean 1974). The chronostratigraphy at HH is based on an accelerator 14C date of the basal sediments and pollen-stratigraphic correlation with the dated BGS core.

  Pollen data from each site were ordinated separately using detrended correspondence analysis (DECORANA; Hill and Gauch 1980) to analyze relationships among species and samples.

• Use:

  This dataset is released to the public and may be freely downloaded. Please keep the designated Contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement. For more information on LTER Network data access and use policies, please see: http://www.lternet.edu/data/netpolicy.html.

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