ANALYSIS OF THE LICHEN COMMUNITIES OF 2 D IFFERENTLY DIEBACK-AFFECTEDPLOTS IN A MAPLE FOREST STAND NEAR QUEBEC-CITY, CANADA

The lichen communities of two differently dieback-affected plots in a maple forest stand at Duchesnay, near Quebec city (Canada), were ident ified and compared together. Cluster analysis of the 44 species found on 17 maple trees (Acer saccharum Marsh.) revealed the presence of two types of lichen communities composed of six different groups. Ordinat ion in reduced space of both communities showed a significant correlat ion between the dieback rate of trees and the species composition of t heir lichen communities. Moreover, the lichen diversity was more impor tant in the most dieback-affected plot where some heliophilous and man y acidophilous species, usually absent on healthy maple trees, were pr esent. The canopy breakdown, associated with the dieback, could be res ponsible for the establishment of these species following the increase of light and the loss of the foliage buffer action.