Search

The carbon (C) dynamics of boreal coniferous swamps are a largely understudied component of wetland carbon cycling. We investigated the above‐ and below‐ground carbon stocks and growing season carbon dioxide (CO2) and methane (CH4) fluxes from a representative boreal coniferous swamp in northern Alberta, Canada in 2022. Tree inventories, understory vegetation biomass and peat cores were collected across three sub‐sites within the broader swamp, with gas flux collars placed in the dominant plant communities present. Alongside the C flux measurements, environmental variables such as water table depth, soil temperature and growing season understory green leaf phenology were measured. Our results show that these boreal coniferous swamps store large volumes of organic C in their biomass and soil (134 kg C m−2), comparable with other wetland and forest types, although 95% of the total C stock at our site was within the soil organic carbon. We also found that understory CO2 and CH4 fluxes indicated that the ground layer of the site is a source of greenhouse gases (GHGs) to the atmosphere across the growing season. However, we did not measure litterfall input, tree GHG fluxes or net primary productivity of the overstory, therefore we are not able to say whether the site is an overall source of C to the atmosphere. This study provides a much‐needed insight into the C dynamics of these under‐valued wetland ecosystems, and we highlight the need for a coordinated effort across boreal regions to try to improve inventories of C stocks and fluxes. Plain Language Summary: Compared to other wetland types across Canada, boreal conifer swamps do not receive the same level of scientific attention and therefore our understanding of how much carbon they potentially store and release is limited. To fill this knowledge gap, our study measured how much carbon was stored both in the trees and within the soil itself, alongside measurements of carbon uptake and release within a representative conifer swamp wetland in Western Canada. We found that although these wetlands may function similarly to other wetland types, by ignoring them, we are missing out on large amounts of carbon being stored in these systems. We also found that at the ground layer, these sites are a source of carbon, that is, releasing more carbon than is being taken up by the understory moss and plant layer. However, we cannot say if the site overall is a source of carbon to the atmosphere as we were unable to measure other key components of a wetland carbon cycle including litterfall input and the productivity of the trees themselves. Our findings indicate that by not including these wetlands in modeling of carbon dynamics, we are missing a substantial component of boreal carbon cycling processes. Key Points: Boreal conifer swamp wetlands are an underrepresented wetland class within wetland C cycling measurements and modelingThese swamps store large volumes of organic C in their aboveground biomass but most importantly, in their soil organic carbon stockWe also found that the ground‐layer of this site is a net source of greenhouse gases during the growing season [ABSTRACT FROM AUTHOR]

Northern peatlands have cooled the global climate by accumulating large quantities of soil carbon (C) over thousands of years. Maintaining the C sink function of these peatlands and their immense long‐term soil C stores is critical for achieving net‐zero global carbon dioxide (CO2) emissions by 2050 to mitigate climate warming. One‐quarter of the world's northern peatlands are in Canada, with these mostly intact ecosystems providing a global C service that is increasingly recognized as a critical part of nature‐based solutions to combat climate change. However, land‐use change and other disturbances threaten these globally important stores of "irrecoverable C" (that is, soil C lost to disturbance that will take centuries to recover). Inadequate policy safeguards to avoid conversion and degradation, and the limited quantification and reporting of peatland greenhouse‐gas emissions and removals, increase the vulnerability of these peatlands. Targeted policies from local to global scales will be needed for improved decision making and incentivizing long‐term C management of northern peatlands. [ABSTRACT FROM AUTHOR]

Oil and gas exploration has resulted in over 300,000 km of linear disturbances, known as seismic lines, throughout boreal peatlands across Canada. Sites are left with altered hydrologic and topographic conditions that prevent tree re-establishment. Restoration efforts have concentrated on tree recovery through mechanical mounding to re-create microtopography and support planted tree seedlings to block sightlines and deter the use of lines by wolves, but little is known about the impact of seismic line disturbance or restoration on peatland carbon cycling. This study looked at two mounding treatments and compared summer growing season carbon dioxide and methane fluxes to untreated lines and natural reference areas of a wooded fen in the first two years post-restoration. We found no significant differences in net ecosystem CO2 exchange, but untreated seismic lines were slightly more productive than natural reference areas and mounding treatments. Both restoration treatments increased ecosystem respiration, decreased net productivity by 6–21 g CO2 m−2 d−1, and created areas of increased methane emissions, including an increase in the contribution of ebullition, of up to 2000 mg CH4 m−2 d−1 over natural and untreated lines. Further research on this site to assess the longer-term impacts of restoration, as well as application on other sites with varied conditions, will help determine if these restoration practices are effective at restoring carbon cycling. [ABSTRACT FROM AUTHOR]

Across Canada's boreal forest, disturbances from in situ oil sands mining, including well‐pads, significantly impact vast areas of the landscape. The creation of well‐pads requires removal of vegetation and placement of mineral fill, which essentially stops any carbon (C) sequestration on the once peatland ecosystem. It is important that, once no longer in use, these well‐pads are restored as long‐term C (peat) accumulation is what defines peatland ecosystem. However, little is known about the recovery of greenhouse gas exchange post‐restoration of these features. We studied a decommissioned well‐pad located in a treed poor fen that was restored using three soil adjustment treatments (SATs): (1) complete mineral fill removal (Peat‐Dec); (2) partial pad removal and burial under peat layer (BUPL); and (3) mixing mineral and peat by inversion (Mixed‐P‐M). The recreated peat surface was revegetated with donor peatland species using the moss layer transfer technique (MLTT). The objectives of this paper were to (1) quantify plot‐scale seasonal carbon dioxide (CO2) and methane (CH4) exchange of the SATs, 2–4 years post‐restoration compared to reference sites and (2) determine the influence of several environmental variables on CO2 and CH4 exchange. All SATs proved effective in recreating a soil surface needed to support peatland vegetation as shown by similar rates of net ecosystem exchange (NEE). Equally, both types of vegetation reintroduced led this site on a trajectory toward functioning as a net C sink. [ABSTRACT FROM AUTHOR]

Carbon dynamics of temperate peat swamps are a largely understudied component of wetland carbon cycling. Under a changing climate, hydrometeorological conditions may change, and understanding how peat swamps may be impacted is important. We investigated the importance of hydrogeomorphic setting on controlling soil carbon dioxide (CO2) and methane (CH4) fluxes from a temperate peat swamp in southern Ontario, Canada over a 3‐year period. We chose three different hydrogeomorphic settings: (a) a site with strong wetland‐stream interactions (i.e., an unconfined stream channel; unconfined), (b) a site with limited wetland‐stream interactions (confined), and (c) an interior site (no wetland–stream interaction). The differing hydrogeomorphic conditions between the sites resulted in differences in carbon fluxes. The unconfined site maintained a higher water table across all three study years, providing conditions that are not favourable to CO2 production. The confined and interior sites sustained a much lower water table, with conditions more conducive to CO2 efflux. The unconfined site also had the highest CH4 emissions due to the increased anoxic conditions favourable for CH4 production as a result of the higher water table position. Hydrogeomorphic setting was found to be important for understanding within site variation, suggesting the sites may respond differently to longer‐term shifts in environmental conditions. This may change relationships between sites if the responses are strong enough to significantly alter carbon fluxes, decomposition, and potential peat accumulation rates. It is important to understand the locally specific responses to environmental conditions within peat swamp ecosystems, in order to make future predictions about whole ecosystem function under changing conditions. [ABSTRACT FROM AUTHOR]