Résultat de la recherche
Ecological determinants of fungal diversity on deadwood in European forests
The fine-scale ecological determinants for wood-inhabiting aphyllophoroid basidiomycetes were investigated with statistical analyses of the occurrence of fruit bodies on woody debris collected in Switzerland and Ukraine. Three substrate descriptors were considered: diameter, degree of decomposition to those local environmental descriptors were detected. Three classes for diameter, as well as for degree of decomposition were thus delimited. They revealed the importance of very small sizes, which were not reported in the literature so far: the relevant diameter class limits were about 0.72 cm and 1.35 cm. Within the host tree species, a clear distinction between coniferous and broadleaf species was found. The next splits followed rather climatic determinants of tree distribution than taxonomical entities such as families or genera. The fidelity of the 59 fungal species to diameter classes, decomposition classes and host tree species was measured by the Dufrene-Legendre index and only significant responses after permutation tests were retained. This brought new insights on the ecology of many wood-inhabiting aphyllophoroid basidiomycetes. Redundancy Analysis was applied to investigate the response of fungal species to diameter and degree of decompostion of woody debris from the most common host tree species, Fagus sylvatica. This direct gradient analysis made it possible to reconstruct the succession of fungal species along the wood decomposition process.
Wood-inhabiting aphyllophoroid basidiomycetes: diversity, ecology and conservation
Wood-inhabiting aphyllophoroid basidiomycetes are a species rich and ecologically significant group in nemoral and boreal forests. They are divided in three major morphological groups: corticioid, poroid and thelephoroid basidiomycetes. The species richness and species distribution depend on several features on different scales: the diversity of the provided substrate, i.e. dead wood, is of vital importance on a smaller scale. On a larger scale the direct (i.e. amount of dead wood, natural likeness) and indirect (i.e. forest fragmentation, distance between fungal populations) impact of forestry highly influences the fungal species richness, additionally to site specific (i.e. altitude, exposition, slope) and regional (i.e. biogeographical region) characteristics. For the quality of dead wood as substrate for wood-inhabiting fungi, three features are most essential: size of dead woody debris, degree of decomposition and host tree species. These characteristics and their combinations create a wide variety of niches subsequently colonised by a great number of fungal species. Especially the often neglected smallest fraction of dead woody debris, i.e. thin branches and twigs, are rich in species. Woody shrub species and thermophilic tree species host a particularly rich fungal species set, as many aphyllophoroid species are host-selective. Additionally, the amount of dead woody substrate is equally important, especially in managed forests. Evidently, the amount and the composition of dead woody substrate are strongly influenced by forest management practices, where most dead wood is cleared and a siteadapted tree cover is often ignored. On a larger scale, the management history of a forest is very important: the time since the last forestry intervention seems a good indicator to predict fungal species richness, at least when dealing with strongly managed Central European forests. Furthermore, if intensive forest management results in habitat fragmentation, the fungal species richness is heavily affected. Fragmentation may not only occur spatially, but also temporally: a break in the availability of the dead woody substrate disrupts the continuity of the fungal life cycle and so causes the local disappearance of populations. When considering the high degree of substrate specialisation of most fungal species, this temporal break in the substrate availability is a major threat for fungal populations in managed nemoral forests. Considering these findings, the remnant patches of natural forest in Central Europe should harbour a considerably higher amount of wood-inhabiting aphyllophoroid basidiomycetes. However, the results of this study are equivocal. Despite the presence of a higher quantity of dead wood and of more diverse dead wood as substrate, which clearly favours the woodinhabiting basidiomycetes, the analyses could not reveal statistically relevant differences.