Effects of prescribed burning regimes on soil fungal communities, functional traits, and community assembly processes in surface and subsurface peat.

Prescribed burning is used to manage peatlands, yet its effects on fungal communities across soil profiles remain poorly characterised. As key mediators of carbon cycling and nutrient turnover, fungi play critical roles in peatland function and resilience. We assessed fungal community dynamics under three long-term prescribed burning regimes (no-burn, long rotations every 20 years, and short rotations every 10 years) at a UK upland peatland. Observed fungal richness declined under short-rotation burning while Shannon and Simpson diversity were lower in burned plots but did not differ between long- and short-rotation treatments. Burn regime and soil depth influenced fungal composition, trophic modes, and functional guilds. Environmental drivers including pH, Ca, Mn, moss cover, and NH₄⁺ varied with depth and were associated with shifts in community structure. Modified stochasticity ratio revealed that stochastic assembly dominated in burned plots, whereas unburned soils showed depth-dependent assembly, with deterministic processes prevailing in 0-20 cm and 40-60 cm layers. Broader niche widths in unburned plots indicated greater generalism. These findings demonstrate that prescribed burning alters community assembly and trophic modes across peat profiles. Disruption of deterministic processes and narrowing of ecological strategies under repeated prescribed burning may reduce microbial resilience, with implications for peatland sustainability.