Ecology and conservation of bryophytes and lichens on Fagus sylvatica

Environmental factors related to the occurrence of epiphytic bryophytes and lichens were examined in beech (Fagus sylvatica) forests in the Province of Halland, Sweden. Patterns in species composition and species number at different temporal and spatial scales were analyzed with emphasis on species of conservation concern (i.e. red-listed and indicator species). (I) At stand level, the availability of substrate, a high stand age and forest continuity were the most important factors explaining high species number of epiphytes of conservation concern. The difference in species number between stands with and without forest continuity was probably related to the presence of old trees and the time available for species colonization. (II) Within stands, plots containing old trees, at the base of slopes and with low recent forestry impact had the highest species number. At tree level, age, size and moss cover were primary factors in explaining both species number and species composition of all species. Red-listed lichens were associated with damaged beech trees older than 180 years, whereas the few red-listed bryophytes were also recorded on younger stems in dense stands. (III) The vertical distribution of epiphytes, recorded on newly fallen beech stems, could also be related to tree age. Some red-listed lichens were recorded only from above 2 m in height on trees older than 250 years. The presence of any species of conservation concern at 2-5 m height on standing living beech trees correlated positively to moss cover and bark structure, which in turn was dependent on tree age. (IV) The effect of bark and tree characteristics on species occurrence was studied. It was found that the combination of high bark pH, high tree age and damaged stem best explained the number of species of conservation concern. The link between old beech trees and high bark pH was partly explained by a positive effect of tree age on stemflow pH. (V) At microhabitat level, the type of stem damage rot hole was found to positively influence bark pH and the occurrence of species of conservation concern. Old and slow-growing trees with rot holes are, however, often removed from managed beech forests. A spatial separation between managed and retention areas is therefore recommended in shelterwood forestry.