Forest fire drives long-term community changes of wood-decaying fungi in a boreal forest archipelago

Abstract: Conservation of wood-decaying fungi requires improved knowledge about the long-term effects of forest management; regarding habitat loss, fragmentation and fire suppression. To better understand such effects, I examined the influence of area, isolation, fire history and forest stand characteristics on communities of wood-decaying fungi. Species richness and composition were studied along a gradient of 22 forested islands varying in size (0.16 to 17.58 ha) and fire history (spanning 5000 years) in a boreal forest archipelago in northern Sweden. A total of 490 records of 41 polypore species were found in 33 circular plots, each 0.1 ha in size. Species richness and the number of red-listed species were analyzed using generalized linear models (GLMs), while species composition was examined using non-metric multidimensional scaling (NMDS) ordination. The species composition was clearly different between recent-fire (< 300 years since last fire) and old-fire (≥ 300 years since last fire) islands, mirroring the shift in tree species composition as pine-associated fungal species were replaced by spruce-associated fungal species. The volume of logs was the only variable influencing the species richness, although the diversity of logs showed a clear trend of also influencing species richness positively. The results demonstrate the importance of having both recent-fire and old-fire forests as landscape-level habitats and species pools, where fire naturally would constitute a key role for maintaining forest biodiversity in the boreal forest landscape. The results also stress the importance of dead wood for species richness at the individual forest stands.