Permanent Plots at Pisgah State Forest in Wincester NH since 1984

There are relatively few studies that have examined forest structure and composition both before and after a catastrophic wind disturbance has altered the forest. On a twenty acre parcel of old-growth forest located in the Pisgah State Forest in southwest New Hampshire, the collection of a long term data set from 1907-1995 has made it possible to consider how the hurricane of 1938 altered forest structure, species composition, and subsequent forest development in the stand. Various types of information were gathered throughout the century that allowed the quantification of forest structure and composition: species identification, diameter measurements, tree status (living or dead), tree cores, and individual tree growth and mortality have recently been tracked. The old-growth forest before 1938 was dominated by a Pinus-Tsuga-Hardwood mix. The hurricane left the forest devastated and incredibly altered. The total basal area of the forest was drastically reduced from approximately 70m2/ha to about 5m2/ha after the disturbance. White pine was effectively lost from the stand while many large Tsuga were also blown down. A large increase in density was subsequently recorded as many post-disturbance species took advantage of the resources that had been made available, especially light. Although there was a high level of destruction, a good amount of Tsuga and Fagus that had previously existed in the understory was released from suppression and grew to fill in parts of the overstory. Both the forest structure and the species composition changed from a relatively homogeneous state before the hurricane to an extremely heterogeneous one after the hurricane. The overall development of the stand followed the typical path of a recently disturbed area: after the initial increase in density in the few years after the storm, basal area has been steadily increasing while density has steadily decreased. It has also been possible to observe differences in the ability of individual species to react to the hurricane. Tsuga and Fagus are exhibiting a much-increased ability to remain in the stand while other post-disturbance species such as Betula and Acer are suffering much higher mortality. Although the forest already has very low tree species diversity, it will continue to drop with time as more and more of the post-disturbance hardwoods are lost to mortality.