Vegetation-derived pyrogenic carbon degradation and stabilisation in UK peatlands†

Abstract

Background Strongly varying timescales of pyrogenic carbon (PyC) degradation have been observed across depositional settings. To date, PyC degradation in UK peatlands has had limited investigation. Aims This study aims to evaluate how PyC recalcitrance relates to differing production characteristics, fuels and duration of exposure in UK peatlands. Methods PyC samples produced from key peatland vegetation types were exposed on a peatland surface to assess molecular (by Fourier-transform infrared), leachable carbon (water-extractable organic carbon) and elemental (C, H, N, O) changes occurring over a year. Key results PyC degradation phases were observed: (1) very rapid (≤1 month) loss of leachable carbon; (2) longer-term (1–12 months) changes to PyC characteristics indicative of soil interactions. ‘Severity’ had a significant effect on all measured variables. Conclusions This study indicates that PyC is susceptible to changes within short timescales in UK peatlands, particularly low-temperature PyC, but that stabilisation through soil matrix interactions may occur over longer periods (>1 year). Implications The findings indicate that UK peatland wildfire carbon cycling research should consider early pulses of carbon to the wider environment, as well as longer-term C storage in PyC.