Fire and local factors shape ectomycorrhizal fungal communities associated with Pinus ponderosa in mountains of the Madrean Sky Island Archipelago

With a warming and drying climate, coniferous forests worldwide are increasingly threatened by wildfires. We examined how fire impacts ectomycorrhizal (EM) fungi associated with Pinus ponderosa, an important tree species in western North America. In the biodiverse Madrean Sky Islands, P. ponderosa forests exist on insular mountains separated by arid lands. How do EM fungi in these isolated ranges respond to fire, and can data from individual ranges predict community shifts after fire at a regional scale? By comparing areas in two ranges that experienced moderate fires 12–16 y earlier, and proximate areas in each range without recent fire, we reveal pervasive effects on diversity and composition of EM communities more than a decade after moderate fires occurred. Post-fire differences in EM communities in different ranges highlight the challenge of predicting fungal community shifts in these isolated forests, despite similarities of climate, plant communities, and fire severity.