Carbon dioxide, methane and nitrous oxide fluxes from a fire chronosequence in subarctic boreal forests of Canada

Abstract

Forest fires are one of the most important natural disturbances in boreal forests, and their occurrence and severity are expected to increase as a result of climate warming. A combination of factors induced by fire leads to a thawing of the near-surface permafrost layer in subarctic boreal forest. Earlier studies reported that an increase in the active layer thickness results in higher carbon dioxide (CO) and methane (CH) emissions. We studied changes in CO, CH and nitrous oxide (NO) fluxes in this study, and the significance of several environmental factors that influence the greenhouse gas (GHG) fluxes at three forest sites that last had fires in 2012, 1990 and 1969, and we compared these to a control area that had no fire for at least 100years. The soils in our study acted as sources of CO and NO and sinks for CH. The elapsed time since the last forest fire was the only factor that significantly influenced all studied GHG fluxes. Soil temperature affected the uptake of CH, and the NO fluxes were significantly influenced by nitrogen and carbon content of the soil, and by the active layer depth. Results of our study confirm that the impacts of a forest fire on GHGs last for a rather long period of time in boreal forests, and are influenced by the fire induced changes in the ecosystem.

Forest fires in Canadian permafrost region: the combined effects of fire and permafrost dynamics on soil organic matter quality

“…The study sites were located in the northern boreal forests of Canada (Fig. S1, Online resource), along the Dempster Highway close to Eagle Plains, Yukon (66°22 0 N, 136°43 0 W), and Tsiigehtchic, Northwest Territories (67°26 0 N, 133°45 0 W), also described in Köster et al (2017). This area belongs to the taiga zone, with annual mean temperature and precipitation of -8.8°C and 248 mm, respectively (Environment and Climate Change Canada 2017).…”

“…We established the study areas in 2015 in forest areas burnt 3 (FIRE 3 ), 25 (FIRE 25 ), 46 (FIRE 46 ) and over 100 years ago (FIRE 100 ), so that together they formed a fire chronosequence, as also described in Köster et al (2017) (Fig. S1, Online resource).…”

“…Biomass for each area was also estimated by determining the tree and ground vegetation biomass (Table S2, Online resource) as described by Köster et al (2017) in each plot. The ground vegetation biomass was measured from four 0.20 9 0.20 m 2 in each plot, while ground vegetation coverage was visually determined from two 0.75 9 0.75 m 2 .…”

Long-term ecological consequences of forest fires in the continuous permafrost zone of Siberia

“…Destroying more than 1% of the global boreal forest each year (van der Werf et al 2006), wildfires have substantial impacts on vegetation structure and composition, the soil organic layer, as well as zoobiota and microbial communities (Viereck and Schandelmeier 1980, Moore 1996, Certini 2005, Waldrop and Harden 2008, Gibson et al 2018. Associated changes are known to modulate nutrient and carbon cycles, surface energy fluxes, and the water balance over the world's largest biome (Amiro et al 2006, Köster et al 2017, Walker et al 2019. Despite an apparent decline in the total global area burned between 1996 and 2015 (Doerr andSantín 2016, Andela et al 2017), the frequency and intensity of boreal wildfires in Alaska, Canada and Russia have increased substantially over the 20th and early-21st century (Soja et al 2007, Turetsky et al 2011, Ponomarev et al 2016, Forkel et al 2019.…”

Carbon dynamics in forest fire affected permafrost soils

“…The locations of sampled fire areas along the Dempster Highway in the Northwest Territories of Canada in Studies I, II and III (modified based onKöster et al (2017).…”