Habitat type and primary colonisation of annual shoots of conifer saplings by epiphytic lichens

The ability of single lichen species to colonise annual shoots of Scots pine ( Pinus sylvestris ) and Norway spruce ( Picea abies ) under a variety of microclimatic conditions was assessed. Lichens were found to colonise the annual shoots of conifer saplings relatively slowly. Hypogymnia physodes is almost invariably the first sorediate species to attach to the bark whereas the other sorediate species appear only exceptionally on shoots in their first couple of years. The age of the substrate seems to be less important to pendulous species, however, probably due to their ability to reproduce also by thallus fragmentation and not only by soredia or spores as most other species do. The majority of the species colonise the annual shoots of spruce faster than those of pine, which suggests that bark exfoliation can effectively hinder colonisation. The colonisation rate of most of the species is clearly reduced under open canopy emphasising the importance of diaspore supply from lichens growing on mature trees.