Wildfire impact on the soil Funga associated to Nothofagus forests from central-western Patagonia, Argentina

Abstract

Climate change projections for western Patagonia, Argentina, predict a 1–3 °C increase in air temperature and a 10–30% reduction in precipitation by the end of this century, which will probably lead to more frequent and intense forest wildfires. Nothofagus are dominant tree species in Andean-Patagonian Forests ecoregion and are known to form symbiotic associations with ectomycorrhizal fungi (EcM). Forest fires threaten EcM, which play a critical role in ecosystem structure and functioning. In this study, we evaluated the impact of recent wildfires in Nothofagus forests on the taxonomic and functional diversity of soil fungi, with emphasis on EcM. Specifically, we aimed to identify fire-resistant fungal species that may contribute to forest restoration programs. To this end, we collected 151 composite soil samples from five paired burned and unburned (control) plots and assessed alpha and beta diversity responses to wildfires based on environmental DNA (eDNA) analysis. Results: Soil fungi species richness was negatively affected by the interaction of wildfire with soil pH and nitrogen content. In contrast, Shannon’s index and Inverse Simpson’s index were positively influenced by wildfires, with calcium, phosphorus, and organic carbon of soil showing significant interactions. EcM species richness was negatively affected by wildfire, whereas diversity indices increased. In the soil fungal community, wildfire led to species turnover, whereas in the EcM community wildfire promoted a nestedness associated with species loss. Additionally, representative operational taxonomic units (OTUs), including Cortinarius sp. and Lyophyllum sp. were primarily associated with burned plots, suggesting their tolerance to wildfire disturbance. Conclusions: In the fungal soil community, wildfire appeared to reduce species richness, while increased evenness, and species replacement. In contrast, the EcM community was largely lost, persisting as a reduced subset of preexisting taxa. Active forest restoration through the inoculation of seedlings with native fire-tolerant EcM species could enhance tree establishment, growth, and survival in post-fire environments.