Epiphytic communities of retention trees of Fagus sylvatica, a case study of SW Germany

Retention trees and retention tree groups are of great value for the conservation of biodiversity: They are home to plant and animal species that have almost disappeared from commercial forests due to forest management interventions. The common beech (Fagus sylvatica L.) is of particular importance here, as it is one of the most dominant deciduous tree species in Central European forests. The present study analyses the contribution of the different tree zones for the epiphytic biodiversity of old beech trees in the montane altitudinal belt zone in the southern Black Forest, SW Germany. Twenty-four large beech habitat trees from 24 different plots were systematically sampled from the base of the trunk to the canopy. All epiphytic plant species (bryophytes and lichens) as well as relevant environmental data were recorded representatively on sample plots of 20 x 30 cm in size, selected by means of specific criteria. A total of 170 species of epiphytes were recorded, including 88 lichens and 82 bryophytes. Using numerical classification, the sample areas were divided into six cluster groups. Five plant communities/associations could be identified: (1) Ulotetum crispae Ochsn. 1928, (2) Dicrano scoparii-Hypnetum filiformis Barkm. 1958, (3) Antitrichia curtipendula community - within the alliance Lobario-Antitrichion Wirth 1968, (4) Usnea dasopoga-Platismatia glauca community - within the alliance Usneion dasypogae Barkm. 1958, (5) Parmelietum furfuraceae Hilitzer 1925. In addition, there were sample plots of dominant bark. This study thus makes a holistic contribution to the knowledge of epiphyte species and their communities on old beech trees, especially by including the little-researched tree crowns.