Abstract
Abstract. Temperate peatland wildfires are of significant environmental concern but information on their environmental effects is lacking. We assessed variation in burn severity and fuel consumption within and between wildfires that burnt British moorlands in 2011 and 2012. We adapted the composite burn index (pCBI) to provide semi-quantitative estimates of burn severity. Pre- and post-fire surface (shrubs and graminoids) and ground (litter, moss, duff) fuel loads associated with large wildfires were assessed using destructive sampling and analysed using a generalised linear mixed model (GLMM). Consumption during wildfires was compared with published estimates of consumption during prescribed burns. Burn severity and fuel consumption were related to fire weather, assessed using the Canadian Fire Weather Index System (FWI System), and pre-fire vegetation type. pCBI varied 1.6 fold between, and up to 1.7 fold within, wildfires. pCBI was higher where moisture codes of the FWI System indicated drier fuels. Spatial variation in pre- and post-fire fuel load accounted for a substantial proportion of the variance in fuel loads. Average surface fuel consumption was a linear function of pre-fire fuel load. Average ground fuel combustion completeness could be predicted by the Buildup Index. Carbon release ranged between 0.36 and 1.00 kg C m−2. The flammability of ground fuel layers may explain the higher C release-rates seen for wildfires in comparison to prescribed burns. Drier moorland community types appear to be at greater risk of severe burns than blanket-bog communities.
Highlights
Peatland wildfires pose a significant global challenge due to their potential for severe effects on ecosystem functioning and the detrimental role they may play in climate change
We aimed to assess how burn severity varied within and between individual wildfires, and to define what the implications of such variation might be for carbon emissions due to wildfire and on-going development of fire danger rating systems such as the Met Office Fire Severity Index (MOFSI; Kitchen et al, 2006)
Most locations in England were broadly classified as mires on deep peat with vegetation dominated by Calluna and Eriophorum vaginatum L. along with species such as Vaccinium myrtillus L., Deschampsia flexuousa (L.) Trin. and Trichophorum caespitosum (L.) Hartm
Summary
Peatland wildfires pose a significant global challenge due to their potential for severe effects on ecosystem functioning and the detrimental role they may play in climate change. Peatlands account for approximately 2.5 % of Earth’s landcover (Kaat and Joosten, 2009) and contain more than 600 Gt of stored carbon (Yu et al, 2010), equivalent to 25 % of global soil organic carbon stocks (Mitra et al, 2005) and 75 % of all atmospheric carbon (Kaat and Joosten, 2009) The degradation of this resource is a potential positive feedback to climate change and smouldering wildfires have other significant environmental and human impacts such as respiratory problems associated with the inhalation of noxious smoke, the significant effort and costs involved in fire fighting, destruction of soil seedbanks, widespread plant mortality and post-fire erosion and water pollution problems (Watts and Kobziar, 2013). Hull (hereafter Calluna) and a variety of mire and bog communities associated with Molinia caerulea (L.) Moench and Eriophorum spp The majority of such habitats are underlain either by deep peat deposits or by shallower organic soils that hold substantial amounts of carbon. Data are urgently needed on both the scale of the wildfire problem and the effects of such burns
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