Fungal trait-environment relationships in wood-inhabiting communities of boreal forest patches

Fungal traits can provide a mechanistic understanding of how
wood-inhabiting fungi interact with their environment and how that
influences community assembly in deadwood. However, fungal trait
exploration is relatively new and almost no studies measure fungal traits
in their environment. In this study we tested species- and
trait-environment relationships in reproducing fungal communities
inhabiting 571 Norway spruce (Picea abies) logs in 55 isolated forest
patches (0.1-9.9 ha) of different naturalness types, located in Northern
boreal Sweden. The studied patches were (1) semi-natural set-aside patches
within highly managed landscapes, or (2) old-growth natural patches
located in an unmanaged landscape. We tested species and trait
relationships to deadwood substrate and forest patch variables. We
measured mean fruit body size and density for each of the 19 species
within communities. Traits assembled in relation to log decay stage and
forest patch naturalness, illustrating the important role of deterministic
environmental filtering in shaping reproducing wood-inhabiting fungal
communities. Early decay stage communities had larger, less dense, annual
fruiting bodies of half-resupinate type and were more often white-rot
fungi. Species rich mid decay stage communities had mixed trait
assemblages with more long lived perennial fruit bodies of intermediate
size, and both brown- and white-rot fungi equally represented. Finally,
late decay stage communities had smaller, denser and perennial fruit
bodies, more often of the brown-rot type. The relationships between the
studied traits and decay stages were similar in both set-aside and natural
patches. However, set-aside semi-natural patches in highly managed
landscapes more frequently supported species with smaller, perennial, and
resupinate fruit bodies compared to natural patches in an unmanaged
landscape. Synthesis We found that log decay stage was the primary driver
of fungal community assembly of species and traits in isolated forest
patches. Our results suggest that decay stage filters four reproduction
traits (fruit body density, size, lifespan and type) and one resource-use
trait (white or brown rot). Our results highlights, for the first time,
that communities with diverse fungal reproductive traits are maintained
foremost across all deadwood decay stages under different forest
naturalness conditions.