Carbon and nitrogen acquisition strategies by wood decay fungi influence their isotopic signatures in Picea abies forests

We examined whether sporocarp carbon and nitrogen isotope ratios (813C and 815N values) reflected different functional strategies in 15 species of wood decay fungi. In Finnish Picea abies forests, we compared sporocarp 813C and 815N against log diameter, proximity to ground, and three wood decay types, specifically brown rot, nonselective white rot, and selective white rot (targeting hemicellulose and lignin preferentially). In regression analysis (adjusted r2 = 0.576), species accounted for 31% of variability in 813C, with factors influencing wood 813C accounting for the remainder. Brown rot fungi and three white rot fungi that selectively attacked hemicellulose (Heterobasidion parviporum, Phellopilus nigrolimitatus, and Trichaptum abietinum) were higher in 813C than nonselective white rot fungi. This was attributed to greater assimilation of 13C-enriched pentoses from hemicellulose by these fungi. The pathogenic white rot fungus Heterobasidion parviporum had higher 815N with proximity to ground and increasing log diameter. This suggested that 15N-enriched soil N contributed to decomposing logs and that Heterobasidion growing from a bigger resource base had increased access to soil N. These isotopic patterns accordingly reflected both functional diversity of wood decay fungi and site-specific factors.

Automated summary

This study investigated the isotopic ratios of carbon and nitrogen in sporocarps of 15 species of wood decay fungi in Finnish Picea abies forests and found that different functional strategies of fungi were reflected in isotopic values. The results showed that the isotopic patterns were influenced by both the functional diversity of wood decay fungi and site-specific factors.