Hemlock Mapped Tree Plot at Harvard Forest since 1990

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.