News Forestry

An old spruce-dominated forest can have close to two thousand species of fungi, and a third of them are found in both soil and dead wood. A third of all fungal species live only in dead wood.

Considerably more species of fungi were found in soil than in dead wood on average. As wood decays, the species’ richness increases, and dead wood in the late stages of decay with a layer of moss on top has as many species as soil.

Dead wood had a local impact on soil fungal community, and a few species were only found in soil in the immediate vicinity of dead wood.

Photo: Erkki Oksanen / Luke

– Isotope analyses indicated that mycorrhizal species colonising dead wood in the late stages of decay actively transfer nitrogen and carbon between soil, dead wood and plants. Large volumes of mycelium of symbiotic species of fungi, such as Piloderma sphaerosporum and Tylospora, which are important for facilitating nutrient uptake for trees, were found in dead wood, explains Dr. Raisa Mäkipää from the Natural Resources Institute Finland.

Species of fungi found in dead wood and soil interact with each other

The study indicated that wood decomposing fungi and fungal communities found in soil interact at all stages of wood decay. This interaction is hugely important for the development of fungal communities and the wood decay process.

– The prevalence of dead wood does not affect the number of fungal species found in soil, but a third of all species of fungi would be locally extinct without dead wood, Mäkipää explains.

The fungal species present were determined by means of molecular biology, by isolating fungal DNA from samples taken from dead wood and soil and by identifying the species or taxons on the basis of the sequences found in the samples. The material for the study was collected from an unmanaged spruce-dominated forest in Sipoo, southern Finland.

This was the first study that compared the fungal species found in soil and the species found in dead wood on the basis of mycelium and not just visible sporocarps. The results indicate that 600 of the species of fungi found in dead wood also live in soil and can survive in a forest regardless of whether or not there is dead wood present. The almost 600 species that only colonise dead wood will disappear if the continued presence of dead wood is not ensured when managing forests.

The study was conducted by the Natural Resources Institute Finland in cooperation with the University of Helsinki. The main sponsor of the study was the Academy of Finland.

The number of fungal species increases as wood decays, and the composition of fungal communities becomes very similar to those found in soil. Decaying logs have an impact on the species of fungi found in soil locally but not the number of species.

Publication: Mäkipää, R, Rajala, T, Schigel, D, Rinne, KT, Pennanen, T, Abrego, N, Ovaskainen, O. 2017. Interaction between soil- and dead wood-inhabiting fungi of an unmanaged Norway spruce stand. ISME Journal, http://doi.org/10.1038/ismej.2017.57