Old growth forest in New England

The rock walls found in every part of the woods in all of New England except northern Maine, are a reminder that virtually all of New England was used for field or pasture at one time in the not too distant past. Only a few parts of New England have what could be considered ``old-growth'' forest, meaning forest that has never been cleared for agriculture or for timber production. One might hope that analysis of these forests would provide a stable endpoint for conservation choices, but the old-growth forests of today are quite different from those of the past.

Foster's [4] analysis of the Pisgah Forest in southwestern New Hampshire provides an instructive example.

• Period of establishment 1635 to 1790 - There were two major establishment episodes in the Pisgah Forest in the last 400 years, one about three and a half centuries ago, from about 1635 to 1700, that accounts for nearly 90% of the pine and hemlock in the forest, and a second, from about 1725 to 1790, that accounts for nearly 90% of the hardwoods in the forest. In most cases, peaks of establishment closely follow known disturbances: fire, hurricanes, or windstorms.

• Period of growth and evelopment 1790 to 1910 - Overstory trees were established by the beginning of this period. Disturbances in the area affected primarily the how rapidly the overstory stems grew.

• Period of extensive disturbance 1910 to 1938 - Chestnut blight entered the area by 1913 and there was extensive mortality by 1915. Windstorms uprooted individuals in 1909, 1915, and 1921. In the 1920's hemlock suffered from a bracket fungus, Armillaria mellea, while porcupines caused extensive damage to beech and birches.

• The hurricane of 1938 - Following 23cm of rain in eight days, about half of the area was moderately damaged. Of the remainder about half was relatively undisturbed and about half was severely damaged, with the severity of damage controlled largely by local topography.
  • The pre-hurricane forest consisted of 300-400 trees ha$^{-1}$ with a basal area 70-90m$^2$ha$^{-1}$ (dbh ca. 1.5-1.9m). Pinus strobus was responsible for 40% of the basal area.

  • In 1984 the density of trees was almost three times higher (1100 trees ha$^{-1}$), but the basal area was less than half of that in the pre-hurricane forest (35m$^2$ha$^{-1}$, dbh 0.6m), and Pinus strobus is almost completely lacking.