Variance in Woody Debris Components Is Largely Determined by the Belowground Microbial Phylum-Level Composition

Although the bioconversion of lignocellulosic residues is essential for nutrient storage in forest floors, little is known about the mechanisms behind wood decay and its interactions with site-specific belowground microbial community composition and chemical properties. This study examined the components of white-rot vs. brown-rot woody debris, closely contacted soil chemical properties and microbial community composition using high-throughput Illumina MiSeq sequencing in coniferous and deciduous temperate forests. The lignin concentrations were higher in the brown-rot than in the white-rot woody debris of the coniferous forest. However, lower cellulose concentrations were observed in the brown-rot sets than in the white-rot sets of both coniferous and deciduous forest stands. Furthermore, the woody debris had higher concentrations of nonstructural compounds and ash in the brown-rot than in the white-rot sets of the coniferous and deciduous forests, respectively. Surprisingly, nearly 90% of the variation in the woody debris components was explained by the belowground fungal and bacterial phylum-level compositions. Of these major phyla, Basidiomycota was closely related to the lignin concentration and accounted for 26.62% of the variation in woody debris components, while Ascomycota was related to the hemicellulose concentration and accounted for 17.7% of the variance in the woody debris components. Furthermore, soil total carbon, available phosphorus, and available potassium were 131%, 138%, and 91% higher in the brown-rot than white-rot sets of the coniferous (but not deciduous) forest stand. In addition, Basidiomycota fungi presented an oligotrophic life strategy and were significantly negatively correlated with the soil total carbon, total nitrogen, alkali-hydrolysable nitrogen, and available phosphorus contents. In contrast, Ascomycota fungi were characterized by a copiotrophic strategy and were positively correlated with the contents of soil total carbon, total nitrogen, and total phosphorus. These findings indicate that wood decay processes are strongly determined by site-specific microbial community structure and nutrient status in temperate forests.