Edge effects on epiphytic lichens in remnant stands of managed landscapes in the eastern boreal forest of Canada

In the managed boreal landscapes of Quebec (eastern Canada), corridors of riparian buffers and upland strips are often the only remnants of productive mature and overmature forests left in the harvested landscape. Because corridors are narrow and have multiple edges, edge effects on forest structure and on epiphytic lichens may be proportionally stronger in these linear remnant habitats than in patchy forest remnants. In this study, we compared the overall biomass of different epiphytic lichen taxa (Bryoria spp., Usnea spp., and Evernia mesomorpha) in four different forest types (linear cutblock separators, riparian buffers, large forest remnants, and control interior forests). We also examined whether edge effects on lichen biomass were present in two types of forest remnants (linear cutblock separators and large forest remnants). Epiphytic lichens were sampled along one transect perpendicular to clear-cut edge in 10 sites within each forest type. We used nested ANCOVA to compare lichen biomass among distance from edge classes and remnant forest types. Bryoria biomass was higher in large forest remnants and interior forests than in riparian buffers and cutblock separators, whereas Evernia biomass was higher in riparian buffers than in other forest types. Usnea biomass did not vary among forest types. On a transect into the forest, Bryoria biomass at 0 and 15 m from the edge was significantly lower than at 30 m. The biomass of Evernia and Usnea was significantly lower at the edge of the clear-cut (0 m) compared to interior plots (30 m). Our results suggest that a landscape where only cutblock separators and riparian buffers are left as remnant mature and overmature forests will not maintain epiphytic lichen communities of mature and overmature interior forests anywhere in the landscape, especially the high biomass of Bryoria observed in interior forests. Wider cutblock separators would be required to maintain core habitat conditions for species associated with late seral stages.