Vegetation structure and fire weather influence variation in burn severityand fuel consumption during peatland wildfires

[摘要] Temperate peatland wildfires are of significant environmental concern butinformation on their environmental effects is lacking. We assessed variationin burn severity and fuel consumption within and between wildfires thatburnt British moorlands in 2011 and 2012. We adapted the composite burnindex (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 usingdestructive sampling and analysed using a generalised linear mixed model(GLMM). Consumption during wildfires was compared with published estimatesof consumption during prescribed burns. Burn severity and fuel consumptionwere related to fire weather, assessed using the Canadian Fire Weather IndexSystem (FWI System), and pre-fire vegetation type. pCBI varied 1.6 foldbetween, and up to 1.7 fold within, wildfires. pCBI was higher wheremoisture codes of the FWI System indicated drier fuels. Spatial variation inpre- and post-fire fuel load accounted for a substantial proportion of thevariance in fuel loads. Average surface fuel consumption was a linearfunction of pre-fire fuel load. Average ground fuel combustion completenesscould be predicted by the Buildup Index. Carbon release ranged between 0.36and 1.00 kg C m⁻². The flammability of ground fuel layersmay explain the higher C release-rates seen for wildfires in comparison toprescribed burns. Drier moorland community types appear to be at greaterrisk of severe burns than blanket-bog communities.

[学科分类] 地球化学与岩石