Author: Student

Acknowledgments
First I would like to thank my supervisors Professor Per Milberg and Dr Karl-Olof Bergman for all their support during this study. I would also like to thank PhD student Håkan Lättman for educating me in identifying difficult species. I would also like to thank the land owners Henric Falkenberg of Brokinds gods and the municipality of Linköping for letting me work on their land. And last but not least a large thanks to Stiftelsen Oscar och Lili Lamms Minne for the financial support to this study.

Tree and site quality preferences of six epiphytic lichens growing on oaks in south eastern Sweden

Contact information
Email: vicjo977@gmail.com
Homepage: http://cms.ifm.liu.se/edu/biology/
master_projects/2007/victor-johansson/

Final thesis
Victor Johansson
International masters programme in Applied biology 2007

Background

Results

Old deciduous trees have become scarce all over Europe, both in forests and wooded grasslands. Groups of species associated to these trees are today restricted to small fragments in the modern landscape where they have trouble surviving because the dispersal possibilities are reduced.
Lichens confined to old oaks (Quercus robur) are one such group of species. Today, one of the most important oak areas in Europe is situated in south eastern Sweden.
Oaks offer a constantly changing environment and a good example of that is the bark going from being smooth on young trees to rough with deep fissures on old. This changes the suitability for different lichen species over time.
Aim:
Describe the tree size preferences of six lichens species growing on oak.
Investigate the effects of other environmental factors: Site quality, light condition, inclination and fissures depth.

Tree size was the overall most important factor. Four species had a positive relationship to increasing tree size and one a negative.
Light affected three species in a positive way.
Inclination had a negative affect on two species.
For two species, site quality affected the colonisation probability and both were found on smaller trees at the site with a larger number of old trees.

Probability of occurrence, in relation to tree size, for one of the species affected by site quality.

Conclusions

Different lichen species have different tree size preferences and also respond differently to the other environmental factors.
The oak has to reach a considerable size/age before several lichen species are able to establish.
A large number of old trees, as potential dispersal sources, could increase the colonisation probability.

Conservation implications

The probability of occurrence and different degrees of lichen cover, in relation to tree size, for two species without site differences.

This study highlights the importance of long-term management plans, that consider the age structure within stands. Trees of different sizes are important to maintain a certain amount of old trees, which are needed for survival of the most demanding lichen species.