Fire history and frequency alter arbuscular mycorrhizal fungal traits, community dynamics, and symbioses

Fire is a common disturbance that structures terrestrial ecosystems. Since climate change models predict increases in fire frequency, it is important to study how changes in fire regime influence plant fuel-related above- and belowground ecosystem components. Due to their role in plant fuel production, arbuscular mycorrhizal (AM) fungal spore communities and symbioses with plants are invaluable for understanding how changes in fire regime influence belowground communities and alter fuel-related above- and belowground processes such as plant growth. With a greenhouse experiment, we tested how variation in fire frequency and history influenced AM fungal community composition, traits, and their interactions with host plants by manipulating fire regimes over three successive generations of AM fungi and Rudbeckia hirta plants. We found that fire frequency effects on spore traits such as pigmentation and sporulation mediated changes in AM fungal spore communities, but these effects took time to develop and were associated with reduced plant growth. This demonstrates that increases in fire frequency can alter the fire-fuel feedbacks that underlie pyrophilic ecosystems.