Response of fungal communities to fire in a subtropical peatland

Purpose Wildfire, an increasing disturbance in peatlands, could dramatically change carbon stocks and reshape plant/microbial communities, with long-lasting effects on peatland functions. Soil fungi are important in controlling the belowground carbon and nutrient cycling in peatlands; however, the impact of altered fire regimes on these fungi is still unclear. Methods We assessed fungal abundance, composition, and diversity across four soil depths (0–5 cm, 6–10 cm, 11–15 cm, 16–20 cm) under low-severity and high-severity fire in a subtropical peatland in the southeastern USA. Results Low-severity fire significantly increased fungal Shannon diversity and saprotrophic fungi in the 0–5 cm soil layer immediately after fire and then retracted within 2 years. This pattern was not observed below 5 cm soils. The dominant fungal class − Archaeorhizomycetes declined initially and then returned to pre-low-severity fires levels at 0–5 cm depths. Time since low-severity fire was a primary driver of fungal composition in the 0–10 cm soil depth, while spatial distance among sites affected the deeper soils (11–20 cm). The fungal Shannon diversity failed to recover in the unburned state even 30 years after high-severity fire, especially in 6–20 cm soil layers. Stratification patterns of the fungal community were diminished by high-severity fire. Soil properties (either phenolics or carbon) were the primary drivers in shaping fungal community reassembly after high-severity fire across all soil depths. Conclusion Collectively, the fungal communities seem to be highly resilient to low-severity fire, but not to high-severity fire in the shrub-dominated coastal peatlands.