Epiphytic lichen response to the edge environment in a boreal Picea abies forest in central Norway

This study has shown a clear edge effect on the green-algal lichen community on spruce branches in a middle boreal spruce forest. Measurements of the following parameters from lower tree branches were carried out at five transects parallel to the SE facing forest edge: species richness, lichen cover, proportion of morphologically aberrant thalli, and size distribution of Platismatia glauca, and length and number of pendulous thalli. The transects were located at 0, 8, 16, 32, and 64 ins distance fromthe edge. The intensity of edge effects are found to be species specific as some species showed pronounced edge response e.g., Cavernularia hultenii, Hypogymnia tubulosa, and Platismatia glauca. In general, the lichen pioneer community distributed on the outermost part of the spruce branches are most affected by the edge environment. A low frequency of small thalli of P glauca and Bryoria spp. at the edge, compared to forest interior, may indicate unsuccessful colonization, depressed growth, or low supply of diaspores at the edge. Wind and snow abrasion at the edge are probably important factors explaining the observed lichen response.