Current issue: 54(5)
Under compilation: 55(1)
The article discusses the adaptation mechanisms of the trees against storms or stormy winds. Two main aspects are revealed: the adjustments of stem and crone and the adjustments of the root system.
The shorter the stem the lower the danger of windfall or windbreak. The wind load of a tree depends on where it is situated; on the open field the wind is much stronger than in closed stand. The tree adjusts its height on the situation: where the wind load is high the trees remain smaller. A tree adjusts its crone also depending on the wind. The branches of spruce are relatively thin and very flexible. An alone standing trees have a flat or umbrella-like crone. Trees with a deep-going main root (tap root) are best protected against windfalls. When there is no tap root, the horizontal roots need to strengthen to offer the needed support.
The protection from windfalls is an important question in the practical forestry. Knowing the factors affecting the wind tolerance of a tree the forest management can be planned to support them.
The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.
There are three theories regarding the stem form of trees. The stem form plays a role in ability of the tree to resist wind and wind breaks. This article presents the theory and experiments about mechanic stem form theory. The wind velocity in a forest stand and the coefficient of resistance at the tree crone and at the tree stem are calculated. The hypothesis about the point when the tree stem breaks is discussed. The approximate values of different calculations are presented.