Mid-term (5 years) impacts of wildfire on soil chemical and biological properties in a UK peatland

Peat degradation due to human activities and global change exposes peatlands to increasing fire risk. Given their key ecological role in carbon storage and water filtration, studying fire impacts on a UK peatland is significant in a global context. This study aimed to assess the medium-term impacts of the 2018 wildfire on peatland soil within the Roaches Nature Reserve (UK). To test whether fire effects were still evident five years after the event and whether marginally affected areas exhibited greater soil recovery, several peat characteristics were evaluated in 2023 at increasing distances from the unburnt control area toward the fire's ignition point, in the order S1, S2, S3 and S4. Results confirmed that the fire effect was still evident after five years, showing a significant increase in pH from 3.59 ± 0.04 in control to 3.85 ± 0.03 in burnt peat, a 60 and 70 % reduction in water and organic carbon content compared to control (65.2 ± 1.33 % and 42.9 ± 1.80 %, respectively), up to 85 % reductions in microbial carbon and nitrogen relative to control (2.48 ± 0.12 and 0.17 ± 0.01 g kg −1 , respectively). The observed spatial gradient of fire impact was: S4 ≫ S3 = S1 ≥ S2, only partially confirming the second hypothesis. As expected, S4 site, farther from the unburnt area, exhibited the worst recovery, but S1 site, proximal to the unburnt area, did not show the highest recovery. This is probably due to the variable nature of peatland fire dynamics and post-fire recovery, highlighting the need for more detailed analyses in future studies. • Wildfire resulted in medium-term consequences on peat properties. • One year after high-fire severity plant cover recovered • Soil microbial biomass nC mic and N mic in burned peat was found to be massively reduced.