Peatland Wildfire Severity and Post-fire Gaseous Carbon Fluxes

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Peatland Wildfire Severity and Postfire Gaseous Carbon Fluxes Alan Gray,1*

G. Matt Davies,2,3,4 Rut Dome`nech,3,5 Emily Taylor,1,6 and Peter E. Levy1

1

Centre for Ecology and Hydrology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK; 2School of Environment and Natural Resources, Kottman Hall, The Ohio State University, Columbus, Ohio 43210, USA; 3Institute for Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow G12 8QQ, UK; 4Solway Centre for Environment and Culture, University of Glasgow, Henry Duncan Building, Crichton University Campus, Dumfries DG1 4ZL, UK; 5Forest Sciences Centre of Catalonia (CTFC), Ctra. de Sant Llorenc ¸ de Morunys, km 2, 25280 Solsona, Spain; 6Crichton Carbon Centre, Maxwell House, Crichton Campus, Bankend Road, Dumfries DG1 4UQ, UK

ABSTRACT The future status of peatlands as carbon stores/ sinks is uncertain given current and predicted environmental change. Several factors can affect the magnitude of the peatland carbon sink including disturbances such as wildfire. There is at present little evidence of how wildfire affects the emission of carbon dioxide (CO2) and methane (CH4) via perturbation to aerobic and anaerobic respiration. The greatest effects, which are likely to vary according to wildfire severity, would be expected in the immediate post-fire stages when little recovery has taken place. Here, we investigate five UK peatland wildfires (2011–2012) in the immediate post-wildfire period measuring CO2 and CH4 fluxes using static chambers. Fire severity was described using a modified form of the composite burn index. A hierarchical partitioning approach indicated time since fire was the most strongly

associated variable that fluxes of both CO2, and CH4 followed by soil temperature for CO2 and fire severity for CH4. Using a liner mixed modelling approach to account for repeated measures; fire severity was a significant term for CH4 and borderline significant for CO2. Mean fluxes of CH4 were consistently lower on burnt sites. In contrast, data from a fire in the north of Scotland appeared to show the opposite relationship for CH4 with higher fluxes on the burnt sites. These results suggest that wildfire can affect gaseous carbon fluxes, but the responses can be variable in both space and time and that disruption to anaerobic processes may be site and/or fire dependent. Key words: Methane; Carbon dioxide; Calluna vulgaris; Canadian Fire Weather Index System; Carbon; Composite burn index; UK.

HIGHLIGHTS Received 16 January 2020; accepted 1 August 2020 Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s10021-020-00545-0) contains supplementary material, which is available to authorized users. Author Contributions AG designed the study, analysed the data and wrote the manuscript. GMD designed the study, assisted with fieldwork and wrote the manuscript; RD completed fieldwork and wrote the manuscript; ET completed field and laboratory work and wrote the manuscript; PL analysed data and wr