Effectiveness of green-tree retention in the conservation of ectomycorrhizal fungi

Habitat fragmentation stresses may reduce the long-term effectiveness of green-tree retention as refugia for ectomycorrhizal fungal (EMF) species. We tested for a minimum retention patch size where EMF species abundance (morphotyping with molecular analysis), richness and reproduction (epigeous sporocarps) aligned with interior Pseudotsuga menziesii habitat on Vancouver Island (Canada). Ten years after logging, species richness was altered along the entire gradient of patch sizes (single trees to 0.12 ha), while % abundance and fruiting had significantly declined for some prevalent EMF species. Retention patches 20 m in diameter, on average, were therefore insufficient in size to ensure the continuity of mature-forest dependent EMF species. Refugia effectiveness would also correspond with habitat extent, and α and γ diversity estimates indicated retention patches approximately 0.2 ha in size, and culminating in at least 3 % of the cutblock area, would capture much of the spatial heterogeneity and species diversity of this EMF community.