Hemlock Mapped Tree Plot

• Investigators: Audrey Barker-Plotkin, David Foster, Ann Lezberg, David Orwig
• Contact: Audrey Barker Plotkin
• Start date: 1990-01-01
• End date: ongoing
• Location: Propect Hill Tract (Harvard Forest)
• Latitude: +42.54
• Longitude: -72.18
• Elevation: 355 meters
• Taxa: Tsuga canadensis (eastern hemlock)
• Keywords: forest dynamics, hemlock, land use, tree maps
• Release date: 1999
• EML version: knb-lter-hfr.31.4
• Revisions: data updated 2007-05-24
• Abstract:

  Most of the central New England landscape was cleared for agriculture in the mid-19th century and then naturally reforested into "secondary forests" with the abandonment of agricultural land. Some sites, often poorly drained, remained forested, but were usually subjected to intensive fuelwood cutting or logging and are termed "primary forests." The Hemlock Woodlot was never cleared for agriculture, but has a history of cutting and natural disturbance. The hemlock woodlot is located in the center of Harvard Forest's Prospect Hill Tract, adjacent to a spruce-blackgum swamp. Soils are moist and rocky, with a thick organic layer. Hemlock dominates tree species composition (62% by basal area), with hardwoods and scattered large white pine comprising the remainder. Most of the trees are 100-150 years old, with a few hemlock trees up to 230 years old. While the site was never cleared for agriculture, it was logged several times and chestnut blight removed a chestnut-dominated overstory in the 1910s. The 0.72 ha stem-mapped plot is at the center of a 4-ha hemlock-dominated forest. This plot serves as a major reference site and is part of a network of hemlock forests that are being intensively sampled as the hemlock woolly adelgid arrives.

• Methods:

  In 1990, the 120m x 60m plot was established with a 10m x 10m grid. The long axis of the plot runs approximately East-West and the 0,0 point is the northwest corner. All trees greater than or equal to 5 cm dbh were mapped using a technique in which inter-tree distances were measured to the nearest centimeter (Boose, E.R., E.F. Boose and A.L. Lezberg. 1998. A practical method for mapping trees using distance measurements. Ecology 79:819-827). For each tree, species, canopy position, health, and diameter were recorded. Trees with multiple stems originating from a single base were measured as separate individuals if the stems forked at less than 1.3m high. Tree diameter and condition was re-measured in 1999; hemlock vigor was also recorded at this time.

  In 2002, sapling density and understory cover was sampled in three 20x20m subplots in or adjacent to the stem-mapped plot. Saplings (a tree greater than 1.3m tall but less than 8cm in diameter) were tallied by species across the site. They were rated as live or dead. We set up two transects running north-south through each 20m x 20m plot for understory vegetation sampling. Five 1 m2 plots were spaced evenly along each transect. 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. We also searched each 20m x 20m plot and compiled a species list. In 2002 a nitrogen cycling study was initiated in the same three 20m x 20m plots.

• 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: HF029