Résumé - CAFD

Edge effects on epiphytic lichens in managed black spruce forests of eastern North America.

Héloise Rheault, Pierre Drapeau, Yves Bergeron, Per Anders Essen.

We studied the spatial and temporal response of three epiphytic lichens (Bryoria spp., Evernia mesomorpha Nyl., and Usnea spp.) to edge effects in conifer forests of northwestern Quebec. Lichen abundance and substrate variables were sampled at four distances (5, 25, 50, and 100 m) from the edge in 15 edge-interior transects in managed black spruce (Picea mariana (Mill.) BSP) forests. Responses to edge effects were assessed for short-term (1-3 years) and long-term (8 and 16-23 years) periods. We also assessed the effect of forest fragment size on lichen abundance in 27 forest fragments ranging in size from 0.03 ha to >4 ha. We found a significant effect of distance to edge on mass of E. mesomorpha and Usnea spp. Lichen mass was lower in the first 50 m of edge compared with the forest interior (100 m). Size of forest fragments had no significant effect in any of the three lichens. However, mass of Usnea spp. was low in the seven smallest (<0.5 ha) fragments. Our results suggest that the response of epiphytic lichens to edge conditions could be used by forest managers as an indicator in determining the size of remnant stands that should be left to increase the proportion of interior forest habitat in harvested forest landscapes. ©2003 NRC Canada