The wood-inhabiting fungal community on standing dead birches : a comparison of ring-barked and naturally dead trees

Abstract: Dead wood is an important part of forest ecosystems, especially since so many organisms depend on it for nutrients or as substrate for breeding or foraging. Since forestry intensified in northern Europe during the mid 1900s, the amount of dead wood in Fennoscandian forests has drastically decreased. For wood-inhabiting organisms such as fungi, this has led to changes in the community composition with many species becoming rare and threatened by extinction. To increase the volume of dead wood, restoration actions aim to create dead wood artificially by for example prescribed burning or by ring-barking trees. In coniferous forests, artificially created dead wood is known to be colonized by many wood-inhabiting fungi, indicating that it can work as a substitute of naturally dead wood. There is, however, a shortage for similar studies in deciduous forests and especially birch dominated ones. In this study, we examine the wood-inhabiting fungal community composition on standing dead wood of birches in east central Sweden. Data was collected with single surveys of fruitbody presence on both ringbarked and naturally dead trees during late autumn. We found that there is a difference in the fungal community composition between the dead wood categories, with form groups of Corticoids and Pyrenomycetes being significantly more abundant on ring-barked birches thanon naturally dead birches. This includes species such as Stereum rugosum and Jackrogersella multiformis. A total of 41 fungal species were observed in this study, out of which 30 species were observed on ringbarked trees and 31 species observed on naturally dead trees. The most observed species was Fomes fomentarius, which appeared numerously on trees of both deadwood categories. Our results indicated that the presence of Fomes fomentarius correlate with lower foraging activity of woodpeckers. However, further research is needed to evaluate if fungal species can be used as indicators for successful restoration actions in relation to the activity of insects and foraging woodpeckers. We conclude that ring-barked birches work well as suitable substrate for many fungal species and that ring-barking as a restoration action is useful for the community of wood-inhabiting fungi.