Current issue: 54(3)
The distribution and occurrence of plant species, including trees, in the nature show that living and splendor of them is constrained by climatic factors. They have their minimum, optimum and maximum for the temperatures they can survive in. The tree species, at least mostly are divided into different varieties in different areas of the world so that the species are most suitable for the climatic conditions of their site.
The article presents the main climatic zones with their tree species according L. Ilvessalo and they suitability to Finland. More accurate areas of suitable species are also listed.
The referred results show that alongside the climatic conditions, the conditions of soil and relief must be taken into account when using exotic tree species for forestry purposes.
The most abundant tree species occur in different variants in different geographical regions. They differ in their genetic, biological and partly also in morphological characters, however making clear difference between these subspecies is not possible. The different subspecies have developed according the respective areas' climatic and soil conditions, developing adaptive characters. These subspecies play a great role in practical forest management, since they differ in for forestry important characters, such as cold tolerance or stem form.
The subspecies hybridize with each other in areas where their distribution areas overlap. In these areas the subspecies cannot be always clearly defined.