Periodic cover silviculture

In periodic cover silviculture forests are managed in cycles which end in a regeneration phase and which are called rotation periods. The purpose is to simulate the natural development of a forest, in which various phases and habitats succeed each other. In southern Finland, the rotation period is 70–80 years, in the north it is longer. At the end of the rotation period the forest is said to be mature for felling or regeneration.

Regeneration begins with a final felling – also called regeneration felling. A final felling can be clear-felling, seedling felling or shelterwood felling. In clear-felling almost all the trees in the forest are felled. In seedling felling, 50–150 seedling trees are retained per hectare; the purpose is that a new forest will grow from the seeds of these after the final felling. In shelterwood felling, trees are left standing to protect the seedlings of a new generation.

After a final felling a new forest is set up either through cultivation – in other words, sowing or planting – or through natural regeneration, if seedling trees were retained during the final felling. After the new seedlings have taken root, the seedling or shelter trees (called hold-overs) are felled. The purpose of setting up a new forest is to shorten the forest's rotation period, which will increase the forest yield.

Only one quarter of the Finnish forests are the result of forest cultivation. The rest have grown up through natural regeneration. It has also been estimated that 80 percent of Finland's current tree stock are the result of natural regeneration. Even in cultivated forests, an average of nearly a third of the seedlings are naturally regenerated.

During the rotation period, seedling stands are managed and thinning is carried out. In thinning, the weaker specimens are generally removed from the forest in order to give more space to the sturdier ones. Thinnings are undertaken 2–3 times during the rotation period, and they increase the financial profit of a forest by as much as 50 percent. In many cases they are also indispensable in safeguarding the biodiversity of commercial forests.

	3. Development of the standing timber stock, distribution of species.
	8. Felling methods, regeneration methods

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