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.