Abstract
PurposeWildfire, 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.MethodsWe 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.ResultsLow-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.ConclusionCollectively, the fungal communities seem to be highly resilient to low-severity fire, but not to high-severity fire in the shrub-dominated coastal peatlands.
Highlights
Peatlands store one third of global soil carbon, with a significant portion of this carbon mass (10–30%) stored in low-latitude regions (Dargie et al 2017; Turetsky et al 2002; Turetsky et al 2015)
Time since low-intensity fire was a primary driver of fungal composition in the 0–10 cm soil depth, while geographical distance among sites affected the deeper soils (11–20 cm)
The fungal Shannon diversity failed to recover to the unburned state even after 30 years after high-intensity fire, especially in 6–20 cm soil depths
Summary
Peatlands store one third of global soil carbon, with a significant portion of this carbon mass (10–30%) stored in low-latitude regions (Dargie et al 2017; Turetsky et al 2002; Turetsky et al 2015). Fire intensity and frequency changes may have cascading consequences for long-term carbon dynamics in peatlands (Kettridge et al 2015; Pellegrini et al 2018; Turetsky et al 2015). Devastating peat-consuming high-intensity wildfires have been increasing due to current climate change, the majority of fire in peatlands are low-intensity (Boby et al 2010; Turetsky et al 2015), which benefit carbon accretion in some peatlands (Flanagan et al 2020). Previous studies showed that high-intensity wildfire had negative effects on soil fungal diversity (Day et al 2019; Hernandez-Rodriguez et al 2013; Holden et al 2013; Martin-Pinto et al 2006), while some studies found increasing fire severity generally had neutral effects on fungal community in boreal wetlands (Whitman et al 2019). Xiang et al (2015) found both low- and high-intensity fire had similar negative effects on fungal alpha diversity
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