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Deadwood

Featuring:Mikko Pirilä, UPM

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Deadwood

sustainable forestry

Deadwood is one of the key elements for biodiversity.

Deadwood refers to dead, decaying wood biomass in forest environment. The deadwood spectrum includes different tree species and parts of a tree of different diameters. In forestry, deadwood usually means trunks with diameters of over 10 cm. This kind of coarse deadwood is formed through natural processes when trees die because of age, competition for resources, severe weather conditions or biotic damages, such as insect infestation. Based on how a tree died deadwood can remain standing until it decays further or already have fallen to the forest floor.

Deadwood is an important structural element of forest ecosystems. It plays a key part in promoting forest biodiversity. Many forest species use decaying wood as a habitat or for food during their lifecycle. There is a wide range of wood-inhabiting fungi and insect species. Epiphyte mosses and lichens live on deadwood. Standing deadwood offers nesting and feeding habitats for many birds. Small-diameter deadwood, such as branches, is inhabited by numerous sac fungi species while polypores are typically found on decaying stems. It has been estimated that one-fourth of forest species in Finland, about 4000 to 5000 species, are somehow dependent on deadwood.

The volume of deadwood in Finnish forests has decreased in the past decades. In the past, the common view was that deadwood had to be taken out of the forest to prevent damage caused by fungi and insects. Deadwood has been integrated into sustainable forestry practices for about 20 years now. Modern guidelines for forest management include instructions aimed at increasing deadwood. The effect of these measures cannot be seen immediately. Inventory results show, however, that deadwood volumes in our forests are on an upward trend again. By saving existing deadwood and leaving retention trees, the future forest stand will have higher amount of deadwood that consists of many tree species in different stages of decay. This will have a positive impact on forest biodiversity.