Fungi and bryophytes on dead wood
Peter Ódor and Jacob Heilmann-Clausen
A major goal in Nat-Man was to investigate the importance of dead wood for biodiversity in European beech forest. A recent report gives a detailed account of the main results of the studies carried out on this subject.
The studies were concentrated on macrofungi and bryophytes since these two organism groups were judged to reflect different aspects of habitat quality. In addition, fungi are main agents of wood decay and are hence of key importance for other saproxylic organisms,
e.g. insects. Altogether 1009 dead beech trees were inventoried for bryophytes and fungal sporocarps in 19 beech-dominated forest reserves across five European countries (Slovenia, Hungary, The Netherlands, Belgium and Denmark).
In total 456 fungal species and 161 bryophytes were identified from the studied trees, showing dead beech wood to be a species-rich substrate. The two most important factors influencing the composition of both fungal and bryophyte assemblages were 1) decay stage of the trees and 2) geographic region. In the case of fungi the effect of decay stage exceeded the effect of geographical difference, while the opposite was the case for the bryophytes. In both organism groups species richness per tree was found to increase with tree size, and to vary with decay stage and between countries. Bryophyte communities were composed of species belonging to widely different ecological groups. The proportion of true epixylic species was highest in Slovenia, somewhat lower in Hungary and very low in the Atlantic region (Denmark, Belgium and the Netherlands). Fungal species considered to be rare and threatened on the European scale (classified as Species of Special Interest) were recorded most frequent in Hungary, slightly less frequent in Slovenia, while they were very infrequent in Belgium and the Netherlands.
Denmark showed intermediate scores. In summary, the Slovenian sites were found to be a
hotspot of bryophyte diversity characterized by high alpha (species richness per tree), and beta (species turnover) diversity, and a high fraction of rare and threatened species. Fungal alpha diversity was low, while beta diversity was high with rich occurrences of rare species. The high value of the Slovenian sites for biodiversity most likely reflects a combination of high air humidity and a very high degree of naturalness. 
Dentipellis fragilis is a fungi species which shows a considerable preferences for the virgin forst in central and southeastern.Europe. In Belgium and The Netherlands the species is missing and in Denmark it is very rare.
The Hungarian stands were characterized by intermediate levels of fungal alpha and beta diversity, intermediate to rather high levels of bryophyte alpha and beta diversity, and very high fractions of rare and threatened fungal species. These characteristics probably reflect the relatively high naturalness of the study sites, as well as the rather continental climate.
In the Danish sites alpha and beta diversity of fungal assemblages were high, while the number of threatened species was intermediate. For bryophytes, alpha diversity was low, while beta diversity was intermediate. These characteristics probably reflect a combination of forest history, present forest structure and climatic traits. Especially the bryophyte mmunities appeared to be impoverished due to lack of forest continuity and forest fragmentation, but still the Danish beech forests seem to have a good potential for restoring rich bryophyte and
fungal communities if more or bigger forest reserves are declared.
The Belgium stands was characterized by high alpha, but low beta fungal diversity, and intermediate alpha, but low beta bryophyte diversity, and a rather low frequency of threatened fungal species. This seem to reflect the favourable climate for growth of both bryophytes and fungal sporocarps in combination with severe impact from past human disturbance.
The Dutch sites are characterized by low fungal alpha and beta diversity, and low bryophyte alpha, but intermediate beta diversity, and very low frequencies of threatened species in both groups. These characteristics clearly relate to the low degree of naturalness of the beech forests in The Netherlands. In both Belgium and The Netherlands the studied saproxylic communities seem to be clearly impoverished as a result of past forest history at the landscape scale, and restoration of communities rich in rare specialist species may be a slow process.
Futher reading
Ódor, P., Heilmann-Clausen, J., Christensen, M., Aude, E., van Dort, K.W. , Piltaver, A. , Siller, I., Veerkamp, M.T., Walleyn, R., Standovár, T., van Hees, A.F.M., Kosec, J., Matocec, N., Kraigher & H., Grebenc, T. 2004. Diversity and composition of dead wood inhabiting fungal and bryophyte
communities in semi-natural beech forests in Europe. Nat-Man Working Report 32.
Variable Slovenia Hungary The Netherlands Belgium Denmark Whole data
number of trees 213 207 197 192 200 1009
Fungi
number of species 207 227 155 190 257 457
number of occurrences 1819 2635 2300 3264 2938 12965
number of species/tree 9.08±8.03 13.11±7.74 11.62±7.40 16.74±8.75 14.69±9.13 12.79±8.65
mean±st.dev
Bryophytes
number of trees 213 207 197 192 200 1009
number of species 103 65 56 48 69 161
number of occurrences 3397 1928 1170 1525 966 8986
number of species/tree 15.95±9.81 9.31±5.31 5.94±4.76 7.94±4.11 4.83±3.66 8.91±7.21 mean±st.dev
Species richness of fungi and bryophyte communities in different countries. Number of species per tree significantly differed among countries for both organism groups.