Current issue: 54(2)
Herb-rich forests are often considered biodiversity hotspots in the boreal zone but their fungal assemblages, particularly those of wood-decaying fungi, remain poorly known. We studied herb-rich forests as habitats for polypores, a distinct group of wood-decaying fungi, and assessed the importance of tree- and stand-scale variables for polypore species richness, abundance, and diversity, including red-listed species. The data include 71 herb-rich forest stands in Finland and 4797 dead wood items, on which we made 2832 observations of 101 polypore species. Dead-wood diversity was the most important variable explaining polypore species richness and diversity, whereas increasing latitude had a negative effect. Red-listed species showed a positive response to the abundance of large-diameter dead wood, which, especially birch, supported also high general abundance of polypores. The composition of polypore assemblages reflected their host-tree species. The red-listed species did not show explicit patterns in the ordination space. Compared to old-growth spruce forests, herb-rich forests seem to host lower polypore species richness and less red-listed species. However, because of high proportion of deciduous trees in the dead wood profile, herb-rich forests have a clear complementary effect on polypore assemblages in boreal forest landscapes.
A field data set representing boreal forest-floor vegetation in Southern Finland was analysed using a simultaneous equation model. Some physical and chemical characteristics of the soil and some structural characteristics of the tree stand were treated as predictors in such a way that the tree stand factor was specified to be dependent on the soil variables. Alpha diversity, measured as the total number of species per plot, was treated as a criterion variable.
The model explains 60% of variance in the alpha diversity indicating markedly strong relationships with the site characteristics. Alpha diversity appears to increase with increases in site fertility characteristics. On the other hand, measured characteristics of the tree stand indicate no significant independent effects on the alpha diversity.
The PDF includes a summary in Finnish.