Occurrence of epiphytic macrolichens in relation to tree species and age in managed boreal forest

For the maintenance of biodiversity some epiphytic macrolichens have been used to identify forests with high conservation value. To understand what these macrolichens indicate, we studied the relationships of tree species and age with the abundance of a set of 33 macrolichens (20 of them in use as indicator species) at 90 localities in a 150 km 2 area in south‐central Sweden. We sampled the four most common tree species Scots pine Pinus sylvestris. Norway spruce Picea abies , birch Betula spp, and aspen Populus tremula for macrolichens at 0‐2 m from the base. Of the 33 target species we found 17, six of them were indicators in use for this region. In 30, out of 40 tested, cases there was a positive relation between lichen abundance and age of the tree. On all tree species the number of the studied lichen species increased with age. The colonisation rate of the species was fastest on birch. All species occurring on birch were also found on at least one of the coniferous trees, while aspen had six species not found on other trees. Pine and spruce with a slow growth rate had more signal lichen species than fast growing trees. We could not detect a competitive situation between common and rare species as the most abundant or largest lichens did not exclude other species. The length of the longest fruticose lichen was positively correlated with the number of species on the tree. Shade had a negative effect on the number of species. We conclude that the indicator macrolichens encountered in this study showed a preference for old trees or aspens. This result, and the low number of indicator species, points at the importance of promoting these trees for the preservation of biodiversity in the boreal forest.