Fire has been used for centuries to generate and manage some of the UK's cultural landscapes. Despite its complex role in the ecology of UK peatlands and moorlands, there has been a trend of simplifying the narrative around burning to present it as an only ecologically damaging practice. That fire modifies peatland characteristics at a range of scales is clearly understood. Whether these changes are perceived as positive or negative depends upon how trade-offs are made between ecosystem services and the spatial and temporal scales of concern. Here we explore the complex interactions and trade-offs in peatland fire management, evaluating the benefits and costs of managed fire as they are currently understood. We highlight the need for (i) distinguishing between the impacts of fires occurring with differing severity and frequency, and (ii) improved characterization of ecosystem health that incorporates the response and recovery of peatlands to fire. We also explore how recent research has been contextualized within both scientific publications and the wider media and how this can influence non-specialist perceptions. We emphasize the need for an informed, unbiased debate on fire as an ecological management tool that is separated from other aspects of moorland management and from political and economic opinions.This article is part of the themed issue ‘The interaction of fire and mankind’.

Abstract:While previous boreal peatland wildfire research has generally reported average organic soil burn depths ranging from 0.05 to 0.20 m, here, we report on deep burning in a peatland in the Utikuma Complex forest fire (SWF-060,~90 000 ha, May 2011) in the sub-humid climate of Alberta's Boreal Plains. Deep burning was prevalent at peatland margins, where average burn depths of 0.42 ± 0.02 m were fivefold greater than in the middle of the peatland. We examined adjacent unburned sections of the peatland to characterize the hydrological and hydrophysical conditions necessary to account for the observed burn depths. Our findings suggest that the peatland margin at this site represented a smouldering hotspot due to the effect of dynamic hydrological conditions on margin peat bulk density and moisture. Specifically, the coupling of dense peat (bulk density >100 kg m À3 ) and low peat moisture (m <250%) at the peatland margin allowed for severe smouldering to propagate deep into the peat profile. We estimated that carbon release from this margin 'hotspot' ranged from 10 to 85 kg C m À2 (mean = 27 kg C m À2 ), accounting for 80% of the total soil carbon loss from the peatland during the wildfire. As such, we suggest that current estimations of peatland carbon loss from wildfires that exclude (and/or miss) these 'hotspots' are likely underestimating total carbon emissions from peatland wildfires. We conclude that assessments of natural and managed peatland vulnerability to wildfire should focus on identifying dense peat on the landscape that is vulnerable to drying.

No abstract

Wildfire is the largest disturbance affecting peatland ecosystems and can typically result in the combustion of 2-3 kg C m À2 of near-surface peat. We hypothesized that organic soil burn severity, as well as the associated carbon emissions, varies significantly as a function of hydrogeological setting due to groundwater impacts on peat bulk density and moisture content. We measured depth of burn (DOB) in three peatlands located along a hydrogeological and topographic gradient in Alberta's Boreal Plains. Peatland margins across all hydrogeological settings burned significantly deeper (0.245 ± 0.018 m) than peatland middles (0.057 ± 0.002 m). Further, hydrogeological setting strongly impacted DOB. A bog with an ephemeral groundwater connection in a coarse-textured glaciofluvial outwash experienced the greatest DOB at its margins (0.514 ± 0.018 m) due to large water table fluctuations, while a low-lying oligotrophic groundwater flow-through bog in a coarse-textured glaciofluvial outwash experienced limited water table fluctuations and had the lowest margin burn severity (0.072 ± 0.002 m). In an expansive peatland in a lacustrine clay plain, DOB at the margins bordering an isolated domed bog portion (0.186 ± 0.003 m, range: 0.0-0.748 m) was considerably greater than the DOB observed at fen margins with a longer groundwater flow path (<0.05 m). Our research indicates that groundwater connectivity can have a dominant control on soil carbon combustion across and within hydrogeological settings. We suggest that hydrogeological setting be used to identify potential deep burning 'hotspots' on the landscape to increase the efficacy of wildfire management and mitigation strategies.

By the end of this century, much of the climate space of western Canada's boreal forest is expected to shift northwards and be replaced by climates that are currently associated with aspen forest, parkland and grassland ecosystems. In this study, we review the various processes that will mediate ecological responses to these projected changes in climate. We conclude that ecological transitions are unlikely to involve a gradual wave-like shift in ecotonal boundaries. Instead, we predict that ecological changes will lag substantially behind changes in climate and that individual ecosystem components will respond at different rates. In particular, if precipitation inputs are maintained as expected, then peatlands should exhibit considerable resilience to climate change and remain a dominant feature on the landscape in 2100. Because peatlands retain large amounts of water on the landscape their continued presence may in turn slow the rate of forest loss, especially the aspen component. Thus, ecological response to climate change in the western boreal region may involve a transition to a novel ecosystem that includes peatlands and aspen as dominant features -unlike anything that exists today. Moreover, this interim stage may remain in place well into the next century, potentially providing additional time for forest-dependent species to adapt.