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DO NOT HIDE FROM RAIN UNDER A FIRTREE

December 15, 2000

Russian scientists have found out that industrial contamination of atmosphere has more impact on flora and soil under the trees and the trees as such than on the space between the crowns. The study has been funded by the Russian Foundation for Basic Research and the President~s grant.

We normally consider a tree as a natural umbrella. It is particularly good to hide from rain under a branchy firtree that is able to hold up to a half of all the water pouring from the sky. However, in industrial zones you should not use a firtree as an umbrella. Rain is contaminated enough there, and after it goes through the crown, it gets even more polluted. This is the conclusion made by V. Nikonov and N. Loukina, researchers of the Institute of Industrial Ecology Problems of the North, Kolsky Scientific Center, Russian Academy of Sciences.
From 1991 to 1997, the scientists were investigating acidity and composition of atmospheric precipitation in the pine and fir tree forests of the Kolsky Peninsular where the SEVERONIKEL copper-nickel industrial complex is located. This industrial complex is one of the most significant sources of industrial air contamination in Northern Europe. Due to its impact, a major part of northern coniferous forests has been affected by acid precipitation, and the dust containing heavy metals, copper and nickel mainly, spreads afar and accumulates on the trees~ crowns.
Rainwater normally changes its composition when flowing through a crown. Water washes away dust, insects~ excrement and plants~ egesta from the crown. Different chemical elements (for instance, carbon, calcium, manganese) are also washed out of it. Thus, precipitation under spruce trees is more acidic and contains more various chemical elements as that in the open spaces among the trees. The level of chemicals is up to ten times higher. In pine tree forests the difference is not so marked.
However, frequent acid rains falling down onto the forests in the vicinity of industrial centers corrode conifer needles and wash out even more ions of calcium, magnesium and manganese. Consequently, the rain becomes more acidic after it has passed through spruce trees branches, and nickel and copper content is increased by 50 to 100 times. Therefore, vegetation and soil under the trees are contaminated to a higher extent, than those in the open spaces among the trees. That is why the most heavily polluted areas have been found under the trees, especially under spruce trees. For this reason the trees are gradually dying, and the forests are getting sparse.
Besides rain, snow is another form of precipitation falling on the northern coniferous forests. Snow covers the trees for 100 to 200 days a year and accumulates and concentrates all atmospheric pollution. Nevertheless, rain has the most negative effect on the trees.
As usual ecologists examine and analyze only open spaces when studying the precipitation effect on the northern coniferous forests. Nikonov and Lukina believe that such analysis produces inaccurate results. In their opinion, it is the soil under the tress that the research should focus on.
The study has been funded by the Russian Foundation for Basic Research and the President~s grant.

Informnauka (Informscience) Agency