Abstract

The decrease in old-growth forests threatens the diversity of a range of organisms. Only a small portion of the forested area in Sweden is formally protected and the majority of unprotected forests are young (<70 years). The objective of this thesis is to provide a deeper understanding of the production forest landscape, with special focus on young forests and to increase the knowledge about man-made substrates. Moreover, this thesis investigates the long-term survival chances of forest bryophytes and lichens, and gives insight into the dispersal biology of bryophytes. After clear-cutting, the remaining dead wood consists of logging residues (slash), logs, snags and man-made high and low stumps. Results from this thesis show that the effect on dead wood supply of harvesting slash for biofuel is most significant for slash and logs. Sixty-five percent of the lying dead wood volume left after clear-cutting was piled for extraction. In addition, 36 % of the remaining dead wood was removed, including a significant volume of coarse dead wood. On stumps in different age classes, bryophytes showed a tendency to increase in richness over time, whereas lichens colonized stands in early succession more rapidly and had an earlier peak in species richness. As a dispersal mechanism for bryophytes living on stumps, ants inhabiting the same substrates were shown to passively carry bryophyte diaspores for a significant period of time. This result sheds light on the complexity of species dispersal. In adjoining young and old forest stands, red-listed bryophytes and lichens were more abundant in the old stands. This difference disappeared when the amount of substrate available was taken into account. When the young stands were positioned north of the old, the bryophytes were equally frequent in both forest stages, indicating that the aspect of a clearcut matters. In conclusion, young forests have the potential to host a high diversity of species. Research on young natural and managed forests is needed to formulate science-based conservation strategies in managed forest landscapes.