Bryophytes associated with two tree species and different stages of decay in a natural fir-beech mixed forest in the Czech Republic.

Species richness and composition of bryophyte communities on two species of trees at different stages of decay were studied on 57 logs of Abies alba and Fagus sylvatica in the natural montane beech-fir forest reserve Salajka (Czech Republic). There were 68 species of bryophytes. At the stand level, the species richness recorded on Fagus was higher than that on Abies. This is due to a higher diversity of epiphytic species on Fagus in the early stages of decay, when the conditions of logs are more heterogeneous and there are more microhabitats than on Abies. The log-level species richness was higher on Abies in later stages of decay because it is more favourable for epixylic species occurring on very acid and constantly moist substrates. Both at the stand- and log level, the highest species richness was recorded at intermediate stages of decay, which constitute a transitional phase in the decay succession in which species associated with all stages of decay overlap and therefore the overall number is relatively high. Species composition differed significantly on the two trees, with two clearly defined groups of indicator species. In contrast, the different stages of decay were not so sharply distinguished in terms of indicator species. We also found significant differences in pH both between the two trees and stages of decay, which may also affect compositional patterns on the logs studied. In conclusion, the species richness and composition of bryophytes on dead wood is associated with both stage of decay and species of tree and their various combinations, which further increase the total diversity. Therefore, successful bryophyte conservation should be focused on the preservation of mixed stands and the continuity of dead wood in the montane beech-fir zone of Europe.