Abundance and diversity of fungi in oak wood

Deadwood is an important functional and structural component of forest ecosystems since it regulates nutrient cycling, serves as a carbon (C) pool, increases the C content in the soil, and is a source of resources, including water, for a wide range of saproxylic and non-saproxylic organisms. The abundance and diversity of wood-inhabiting fungi in six fallen, horizontally lying logs of Quercus petraea, in the 1st, 2nd and 3rd decay classes, in the Drawa National Park in Poland in 2015, were studied using the Illumina se- quencing technique. The total number of OTUs obtained (264 307) included sequences of culturable fungi (242 369 = 91.70%) and non-culturable fungi (7 056 = 2.66%). The dead oak wood was colonized by 277 taxa. Culturable fungi of Zygomycota, Ascomycota and Basidiomycota comprised 75% of taxa detected and were represented by 14, 139 and 53 taxa respectively. Non-culturable organisms were represented by 70 taxa. Fungi were classified into 18 groups: (i) typical soft rot fungi, (ii) phytopathogens potentially hazard- ous to trees, (iii) epiphytes and endophytes or weak, opportunistic pathogens, (iv) ectomycorrhizal species, (v) ericoid mycorrhizal species, (vi) crust fungi, (vii) resupinate basidiomycetes, (viii) saprotrophs and soil fungi, (ix) opportunistic human pathogens causing superficial or systemic mycoses, (x) pathogens of warm- or cold-blooded animals, (xi) ascomycetous yeasts, (xii) basidiomycetous yeasts, (xiii) antagonists of fungi, (xiv) producers of metabolites effective against pathogens, (xv) hyperparasites, (xvi) lichen-form- ing species, (xvii) partners of other fungi, (xviii) species rare or uncommon in nature. It was shown that: (i) coarse, woody debris of oak is host to abundant and diverse mycobiota, (ii) abundance and diversity of fungi increase with the decay continuum, (iii) oak logs can be a habitat of phytopathogens potentially haz- ardous to forest health, (iv) different phytopathogens favour wood in different decay classes, (v) abundance of pathogens decreases, and of ericoid mycorrhizal (or soil) species increases with the decay continuum. Maintaining different types of deadwood increases fungal diversity, but also the risk of diseases.