Acid Rain Effects Acid Rain  Elmhurst College
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Acid Rain Effects on Forests

Effects on Forests:

Some of the most dramatic effects on forests have been observed in Europe. In 1983, a survey in West Germany showed that 34 % of the country's total forest is damaged by air pollution. This included about one half of the famous Black Forest. Switzerland has recorded damage to 14 % of her forest trees.

Red spruce and Fraser firs are dead and dying on top of Mount Mitchell, North Carolina. There are few signs of any plant life reproduction there.

A large number of trees are falling prey to insect and disease attack resulting in die back of trees in New England states as shown in the graphic on the left.

On Camels Hump in Vermont's Green Mountains, Dr. H. Vogelmann, professor of botany at the University of Vermont, has reported startling evidence of tree damage. Conifers are most effected because the needles are bathed in acid droplets all year around.Other trees drop their leaves. Measurements of the total biomass in the balsam fir has declined 20 % from 1965 to 1983. The red spruce has declined a dramatic 73 % in the same time period. Lower on the mountain sugar maples and beech trees biomass dropped 25 %.

Forests at high altitudes maybe enshrouded by clouds or fog for much of the time. The pH of lower cloud droplets may average 3.6, which is a much lower pH than the final rain of pH 4.2.


Forest Damage:

The graphic on the left is a special infrared photo of Mount Marcy, N.Y. Dying trees are blue gray, healthy are red.

Vogelmann, measured the reproductive capacity of the forest by counting the total trees in an area. Red spruce dropped from 6,000 trees to 1,000 trees, a decline of 80 % from 1965 to 1983. Very few pine cones and young trees were found. Sugar maple tree counts dropped 84 % and Beech tree counts dropped 63 % over the same time period.


Tree Ring Analysis:

Scientists from the University of Vermont bored hundreds of trees of different species. They found that the growth rate of the trees began to decline in the late 1950's. The closer spacing on the right shows less growth as seen in the graphic on the left.

Chemists have analyzed the wood cores of a 100 year old sugar maple and a 200 year old red spruce. The analysis was designed to find changes in various metal ion concentrations over the long period of time.

In the 1950's aluminum begin to increase until it is now three times higher than in the pre-1950 era.

Nutrient Leaching:

Acid rain or acid cloud droplets that fall on the leaves and needles of trees leaches the nutrients from them. Calcium, magnesium, and potassium ions may be removed from the leaves faster than the roots can resupply them. Acid rain in combination with ozone may damage the waxy coating on leaves and needles. This may weaken, damage them, and provide opportunities for diseases to enter the tree.