Strong reasons to worry about the long-term health of Northeast forests are coming from new, detailed studies of the effect of chronic pollution on mature trees, scientists report.
After 11 years of experiments and surveys in three Northeast forest areas, researchers conclude that near-constant exposure to nitrogen-rich chemicals, from sources such as acid rain, reduces the vigor and growth of evergreen trees. Some evergreens are killed. Airborne ozone also is detrimental, they said.
Although the extra nitrates contributed via pollution act as a fertilizer, initially spurring tree growth, long-term additions of nitrates eventually saturate the ground, causing nutrients such as calcium, manganese and potassium to become mobile and leach out of the soil.
The soil becomes poor, less able to support tree growth.
Worse, as nitrate pollution continues, aluminum is mobilized in the soil, poisoning fish, such as trout, by disrupting normal function of their gills.
Ozone, a common pollutant that flows through Northeast forests, also has large impact. The latest estimates are that primary forest production -- the growth of wood -- is being reduced by about 10 percent, on average. Ozone is harder on deciduous trees, including hardwoods such as oak, maple and birch, because of their relatively fast rates of respiration.
The studies were conducted by forest ecology specialists at the universities of New Hampshire, Maine and Minnesota, the Woods Hole Marine Biology Laboratory and the U.S. Forest Service.
Pub Date: 2/04/99