Determinants of Deadwood-Inhabiting Fungal Communities in Temperate Forests: Molecular Evidence From a Large Scale Deadwood Decomposition Experiment

Abstract

Despite the important role of wood-inhabiting fungi (WIF) in deadwood decomposition, our knowledge of the factors shaping the dynamics of their species richness and community composition is scarce. This is due to limitations regarding the resolution of classical methods used for characterizing WIF communities and to a lack of well-replicated long-term experiments with sufficient numbers of tree species. Here, we used a large scale experiment with logs of 11 tree species at an early stage of decomposition, distributed across three regions of Germany, to identify the factors shaping WIF community composition and Operational Taxonomic Unit (OTU) richness using next generation sequencing. We found that tree species identity was the most significant factor, corresponding to (P < 0.001) and explaining 10% (representing 48% of the explainable variance) of the overall WIF community composition. The next important group of variables were wood-physicochemical properties, of which wood pH was the only factor that consistently corresponded to WIF community composition. For overall WIF richness patterns, we found that approximately 20% of the total variance was explained by wood N content, location, tree species identity and wood density. It is noteworthy that the importance of determinants of WIF community composition and richness appeared to depend greatly on tree species group (broadleaved vs. coniferous) and it differed between the fungal phyla Ascomycota and Basidiomycota.

Keywords: BELongDead; fungal community composition; fungal richness; microbial ecology; next generation sequencing; wood-physicochemical properties.

FIGURE 1

Wood physicochemical properties of deadwood logs decomposing for 3 years across 11 tree species (green = broadleaved tree species and red = coniferous tree species) in 27 forest plots (mean ± SE, n = 27). The maximum and minimum values are represented by the orange and blue dotted lines, respectively.

FIGURE 2

Variation partitioning analysis for evaluating the most important factors explaining the variations in wood-inhabiting fungal community composition (A,D,G = all fungi, B,E,H = Ascomycota, and C, F, I = Basidiomycota).

FIGURE 3

The overall architecture of tree family–fungal associations illustrates how wood-inhabiting fungal OTUs that show preferences for particular tree species (detected in no more than two tree species, in total 617 OTUs) were distributed within a web of wood-inhabiting fungi. Different node shapes represent different organismic groups: square nodes = plant families (number of tree species in each family is shown in the middle of each node) and circular nodes = fungi (yellow nodes = fungal OTUs associated with Pinaceae and white nodes = fungal OTUs associated only with broadleaved tree families; the numbers of fungal OTUs associated with each family and tree species are shown in brackets).