Assessment of the health and sustainability of New York forests based on forest structure, mortality, and disease.

摘要

The health of a forest is its ability to sustain itself if left undisturbed, or to recover rapidly if disturbed. Forest health is best addressed on a relatively large spatial scale. Although individual trees or stands of trees within a region may be undergoing change or disturbance, they do not impact forest health significantly if they are compensated for by complementary changes elsewhere. One method of assessing the health of forest populations is to calculate the baseline mortality rate per diameter class that would sustain the current size-class structure based on the slope of a regression line fit to the natural logarithm of stem density across diameter classes. Chapter 1 shows that in mature forested regions it is likely that such a diameter distribution will be negative exponential, meaning that the baseline mortality per diameter class will be constant across diameters. Chapter 2 evaluates the potential effect of a large 1998 ice storm in northern New York by testing the shape of diameter distributions, immediately after the storm and then with simulated storm-related mortality. Seven of ten species analyzed had negative exponential diameter distributions initially, and simulations indicated that the shape of two of those might be altered significantly by the ice storm. In Chapter 3 an index of actual mortality was developed for two populations of Acer saccharum and one of Fraxinus americana, based on the cumulative effect of different disease and injury liabilities on a tree. For the Adirondack Park population of A. saccharum the index exceeded baseline mortality rates in large diameter classes. It was consistent with baseline mortality rates in other populations. Chapter 4 defines and describes community types throughout New York based on the tree species composition of a large random sample of inventoried state-owned forest stands. The sustainability of each community type was assessed based on simulated past and future mortality. State-owned land in New York is composed mostly of northern hardwood, disturbance, and plantation forest communities. Planted stands transitioned toward species characteristic of the disturbance community group, and the disturbance stands transitioned toward species characteristic of the northern hardwood group.