Thinning of young spruce stands in conditions of air pollution : Treatment of young forest stands. IUFRO-Proceedings

1989

S. 66-73

2 Abb., 3 Tab., 9 Lit. Ang.

Unselbständiges Werk

200086088

In Bohemia there are 52 % of forest stands affected by air pollution. More than 85 % of all these air polluted stands belong to the slithtly affected areas. Growing conditions of these forest stands make possible to use specific silvicultural traetments in order to achieve appropriate production. Thinning in relatively slightly polluted spruce stands are rather problematic because these stands grow mainly in areas subjected to frequent snow damage. In order to increase the static stability of spruce stands, the concept of growing in loose canopy was accepted in silvicultural practice in the last 20 - 30 years. This concept is based on the ability of spruce to respond to loose canopy by more intensive growth of dbh and by increased resistance to snowbreak. The loose canopy, at the same time, leads to the risk of more intensive penetration of air poolution into the forest stand and to consequent damage of crowns by sulphur dioxide. The problem of thinning of young spruce stands in air polluted areas under the risk of snow damage was investigated by classical comparative methods during the period of ten years. Attention was paid to the growth of trees and their health condition and to the content of sulphur in needles. The results of this investigation show that the sulphur content of upper parts of crowns in heavy thinned young spruce stand increased nearly by 20 %. In spite of this, the growth of dbH was the same as in the stands without air pollution and the health condition of trees was not getting worse. The results of the experiments allow to recommend the heavy thinnings as a method suitable for young spruce stands slightly damaged by air pollution.