Disturbance and diversity of wood-inhabiting fungi: effects of canopy gaps and downed woody debris

Experimental canopy gap formation and additions of coarse woody debris (CWD) are techniques intended to mimic the disturbance regime and accelerate the development of northern hardwood forests. The effects of these techniques on biodiversity and ecosystem functioning were investigated by surveying the abundance and diversity of wood-inhabiting fungi in six treatments: (i) unharvested control, (ii) control + fenced to exclude deer, (iii) gap creation + fenced to exclude deer, (iv) gap creation, (v) gap creation + CWD addition, and (vi) CWD addition under closed-canopy. A total of 1,885 fungal occurrences (polyporoid and corticoid fruiting bodies) representing 130 species were recorded on 11 tree species, with eight fungal species accounting for 52 % of all observations. A linear mixed model demonstrated significant differences in the abundance and diversity of wood-inhabiting fungi by treatment, with the gap creation + CWD addition treatment supporting the highest abundance and richness of fungal species. Non-metric multidimensional scaling demonstrated that stumps, sugar maple substrates, medium (20 to < 25 cm) and large-diameter (> 40 cm) substrates most strongly influenced fungal species occurrences. Rarefaction curves indicated that smaller diameter substrates (< 20 cm) supported a rich fungal community, yet substrates in the largest diameter class (> 40 cm) supported nearly 25 % of all fungal species detected. Rarefaction curves also highlighted the importance of well-decayed substrates and minor host tree species. A subset of fungal species was significantly more abundant in gap treatments. The results indicate that wood-inhabiting fungi are responsive to forest management intended to promote the structural attributes of old-growth northern hardwood forests.