Community structure of wood-decaying fungi along a stand-replacing wildfire chronosequence in southwestern ponderosa pine forests

Background/Question/Methods: In southwestern ponderosa pine forests, recent severe fires have caused dead wood to comprise the predominant aboveground carbon storage pool on burned landscapes. The decay of dead wood contributes to the release of CO2 to the atmosphere via microbial respiration, but the controls on this process are not well understood. In particular, very little is known about the fungal community responsible for the majority of wood decomposition. This is especially true in the semi-arid Southwest, where above ground sporocarp surveys can poorly represent fungal communities because of limited fruiting. We investigated the effects of stand-replacing wildfire on fungal community structure using paired burned and unburned sites along a wildfire chronosequence (burn years: 1977, 1984, 1996, 2000, and 2005). We predicted that fungal species composition would vary both with time and as a consequence of fire. To address this question, we sampled wood from logs at the chronosequence sites and cultured the fungi from within the wood. We extracted DNA from the mycelial isolates and used restriction fragment length polymorphism (RFLP) and DNA sequencing to identify fungal community structure (species richness and composition). Results/Conclusions: We observed greater fungal species richness in logs from unburned sites compared to those from burned sites. Among the burned sites, species richness peaked in the intermediate-aged burns, suggesting a higher diversity of carbon substrates in the wood at these sites. Our data provide an important link between microorganisms and the process of wood decomposition and suggest that stand-replacing wildfire disturbances profoundly influence the community structure of wood-decay fungi.