Hemlock Understory Vegetation Plots

• Investigators: Audrey Barker Plotkin, David Foster, David Orwig
• Contact: Audrey Barker Plotkin
• Start date: 2002-01-01
• End date: ongoing
• Location: Prospect Hill Tract, Slab City Tract (Harvard Forest)
• Latitude: +42.45 to +42.55
• Longitude: -72.22 to -72.18
• Elevation: 250 to 350 meters
• Taxa: Tsuga canadensis (eastern hemlock)
• Keywords: hemlock woolly adelgid, Tsuga canadensis, understory vegetation
• Release date: 1999
• EML version: knb-lter-hfr.48.2
• Revisions:
• Abstract:

  Hemlock (Tsuga canadensis) forests in New England are changing rapidly with the invasion of the hemlock woolly adelgid (HWA, Adelges tsugae), an exotic insect pest that kills hemlock trees. The adelgid is just beginning to be observed at Harvard Forest, making this the right moment to begin intensive physiological, ecological and monitoring studies of our hemlock forests. We gathered detailed baseline information for several hemlock stands across Harvard Forest. We surveyed community vegetation structure and composition, and began to monitor soil nitrogen cycling. These measurements will allow us to link the long-term history of these hemlock stands to other current studies of hemlock response to adelgid infestation, and will provide the basis for intensive study of hemlock dynamics with the stands' anticipated decline.

  Nearly all saplings were hemlock; sapling densities ranged from 183-1645 stems/ha. Understory flora characteristics were sampled in 10- 1m2 subplots within each overstory plot. Across all sites, herb and shrub cover was very low, reflecting the dense shade and deep organic layer present in these hemlock stands. Species richness ranged from 6-15 understory species found in each 20x20 or 30x30m plot.

• Methods:

  In 2002, we set up two transects running north-south through each of the following plots for understory vegetation sampling. Five 1 m2 subplots were spaced evenly along each transect. We labeled the NW corner, unless otherwise marked. Transects are marked with string and yellow tent stakes (no string at Jenkins plots), and plots are marked with pink flags.

  We estimated percent cover for herbs, shrubs, and seedlings to the nearest one percent. We counted the number of seedlings by species. A seedling is a tree less than 1.3m tall. If rocks or coarse woody debris covered a significant portion of the plot, their percent cover was recorded. In addition, the depth of the organic soil layer was measured to the nearest 0.5 cm at the NW corner of each subplot. We searched each plot and compiled a species list for the entire 20m x 20m or 30m x 30m area.

  Saplings were tallied by species across the plot. A sapling is a tree greater than 1.3m tall but less than 8cm in diameter. They were noted live or dead.

• 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.

• Related datasets: HF036 HF053 HF083