Deeper burning in a boreal fen peatland 1‐year post‐wildfire accelerates recovery trajectory of carbon dioxide uptake

Abstract

Peatlands contain a globally significant store (30%) of soil carbon (C). Within the Canadian Western Boreal Plains, where peatlands are a dominant feature, the climate is becoming warmer and drier, coupled with an increase in forest fire incidence. The response of peatlands to forest fire is likely to be a key determinant in the future of C storage of Boreal peatlands. This study examined the impacts of fire on key environmental controls on CO2 fluxes at the plot‐scale (using static chambers) between burned and unburned understory vegetation throughout the growing season of 2017 in a treed fen impacted by the Horse River wildfire (2016) in Fort McMurray, Alberta, Canada. Both gross ecosystem productivity (GEP) and total respiration (Rtot) were less at burned plots compared with unburned. Temporal patterns varied between the plots, where both component of CO2 fluxes at the unburned plots were largest in June, whereas at the burned plots, CO2 fluxes peaked in the late growing season. GEP and net ecosystem exchange (NEE) showed a positive relationship with depth of burn, with the deepest burned areas showing significantly greater CO2 uptake, coinciding with both increased bioavailable phosphorus and greater moss recolonization. At the unburned plots, soil temperature was a dominant control on CO2 fluxes. This work demonstrates the importance of the depth of burn to post‐fire carbon fluxes and how a knowledge of burn severity and depth can inform understanding of the recovery trajectory of northern peatlands following fire disturbance.

Loss and Recovery of Carbon in Repeatedly Burned Degraded Peatlands of Kalimantan, Indonesia

“…We should emphasize that for the estimates of carbon loss, the authors used a lower peat bulk density value of 0.115 g cm −3 but greater carbon content of 55.3% compared to our field measurements of 0.150 g cm −3 and 45.6%. Consistent with the findings from other studies [14,15], degraded peatlands have compact peat with bulk densities much greater than 0.115 g cm −3 which is more representative of undisturbed peatlands [10]. Our previous analyses have shown that C% of 39-43% is a more realistic value for the degraded peatlands [6]-well below the almost universally used 56% reported by Page, Rieley and Banks [1]-irrespective of peat degradation status.…”

“…The top layer of peat lost about 5% of carbon compared to unburned sites (Table 2). However, both the burned and unburned sites in these degraded peatlands had lower C% than relatively undisturbed peat forest, e.g., 51% for the top layer in the Sebangau National Park, [6], 54% reported by [10] or 56% averaged for the whole of South East Asia by [1]. The impact of recurrent fires on C% (also called Corg) has been greatly understudied [5].…”

Shortening fire return interval predisposes west‐central Canadian boreal peatlands to more rapid vegetation growth and transition to forest cover

“…Ecotones are at greatest risk for fluctuations in water table (Dimitrov et al., 2014), flooding (Lukenbach et al., 2017; Ingram et al., 2019), and deeper burns (Hokanson et al., 2016; Morison et al., 2021; Lukenbach et al., 2017; Wilkinson, Tekatch, et al., 2020; Wilkinson, Verkaik, et al., 2020) resulting in greater environmental extremes and more rapid changes that could either enhance vascular vegetation growth or induce mortality especially following SRI fires. Here, peatland ecotones and adjacent peatlands demonstrated significantly greater changes in both rates of vegetation growth and decline (Figure 4) as well as the proportional area of vascular vegetation within peatlands and ecotones (Figure 5) following SRI as opposed to LRI fires.…”

Post-fire peatland vegetation recovery: a case study in open rich fens of the Canadian boreal forest

“…Although the fires of the fen studied were relatively recent and the fire events limited (only three fire events were studied), post-fire vegetation evolution suggests that northern burned rich fens are regenerating towards unburned natural fens, without major changes in the vegetation composition and microstructure. However, in the context of climate change where extremely dry seasons and fires may occur more often (Turetsky et al 2015), this may trigger a shift from moss dominated fens to shrubbier peatlands (Kettridge et al 2015;Sulwi nski et al 2020;Nelson et al 2021), and affect their ecological functions (Morison et al 2021). Five years post-fires, there was no complete return of the plant diversity and abundance, but brown mosses recovered to more than half their natural cover.…”

“…Though, with the increase of fire occurrence and extent in Western Canada over the last half-century (Hanes et al 2019), and with the expected increase of fire occurrence due to climate change (Wotton et al 2010;Whitman et al 2019), the impact of fire on boreal peatlands, both for bogs and fens, is likely to change in the future (Turetsky et al 2015). Permanent changes in the vegetation composition and the microtopography structure following a fire may seriously impact boreal fen functioning, for example by modifying their carbon storage potential (Turetsky et al 2002;Morison et al 2021). Very little is known regarding the fire severity and impact in fens dominated by brown mosses and their recovery after a fire.…”