Dead wood and fungi : detection, diversity and conservation in boreal forests

Abstract

Dead wood and associated fungal communities are a crucial part of boreal forest ecosystems, and severely affected and threatened by human actions like commercial timber harvesting. Despite their importance for forest functioning, most wood-inhabiting fungal species, especially those producing small fruit bodies, are still ecologically and taxonomically poorly known. In addition, studies on dead wood profiles have neglected fine woody debris. This thesis includes detailed investigations of fruiting phenology of different morphological groups and complete dead wood profile of one semi-natural boreal forest. In addition, the diversity patterns of wood-inhabiting fungal communities according forest continuity and naturalness as well as dead wood quality were studied in 14 semi-natural forests. In addition to species richness the relationship between species traits and substrate quality was explored. The fruiting phenologies and dead wood profiles differed between fungal groups and dead wood tree species, respectively. Forest continuity and naturalness had a positive but weak effect on species richness, substrate continuity being important for Micarea lichens. Tree species had strong influence on fungal community composition. Broadleaved dead wood hosted the highest species richness, especially discomycetoid and pyrenomycetoid fungi specializing on it. Pileate fungi were found specializing on spruce and were the only group having positive response to forest naturalness at the substrate level. Especially discomycetoid and pyrenomycetoid fungi inhabiting pine had positive relationship with forest naturalness at the site level. Species had on the average larger spores on broadleaved than conifer dead wood, and the spore size increased with log size. In conserving dead wood and its fungal inhabitants, the tree species- and fungal group-specific responses need to be taken into account. Standing and downed dead pine is a special case as considering species inhabiting it in management planning requires time scale of a millennium rather than centuries.