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Wetlands are an integral part of the Canadian landscape, providing crucial ecohydrological services with globally significant benefits. Over the past 75 years, Canadian scientists have emerged as international leaders in wetland hydrological research, contributing to a better understanding of wetland form and function. Early Canadian research was instrumental in the development of a classification scheme that provided a foundation for later investigations into vadose zone processes, solute transport, evapotranspiration, ground-ice dynamics, biogeochemical cycling, and modelling. This work has coalesced into a better understanding of the factors that contribute to wetland presence and persistence on the landscape, and the internal processes that result in their unique functions of carbon sequestration, water storage, flood mitigation, water quality enhancement, and wildlife habitat. In Canada and across the world, wetlands are threatened at a range of scales and intensities by disturbances like climate change, resource extraction, wildfire, altered land use, and contamination. In response, Canadian researchers have become global leaders in characterizing the impacts of disturbance on wetland function and been at the forefront of innovative restoration and reclamation techniques. As the value of wetlandisre increasingly acknowledged by stakeholders and decision-makers, the need for evidence-based wetland research will only continue to grow. Canadian scientists are well-positioned to lead wetland hydrology into the next 75 years. Les milieux humides font partie intégrante du paysage canadien, offrant des services écohydrologiques essentiels avec des avantages d'importance mondiale. Au cours des 75 dernières années, les chercheurs canadiens se sont imposés comme des leaders internationaux dans la recherche hydrologique sur les milieux humides, contribuant à une meilleure compréhension de leur forme et de leur fonction. Les premières recherches canadiennes ont joué un rôle clé dans l'élaboration d'un système de classification qui a servi de fondement à des études ultérieures sur les processus de la zone non saturée, le transport des solutés, l'évapotranspiration, la dynamique de la glace du sol, le cycle biogéochimique et la modélisation. Ces travaux ont mené à une meilleure compréhension des facteurs qui contribuent à la présence et à la durabilité des milieux humides dans le paysage, les processus internes qui donnent lieu à leurs fonctions uniques de séquestration du carbone, de stockage de l'eau, de mitigation des inondations, d'amélioration de la qualité de l'eau, et d'habitats fauniques. Au Canada et partout dans le monde, les milieux humides sont menacés à diverses échelles et intensités par des perturbations telles que le changement climatique, l'extraction de ressources, les feux de forêt, l'utilisation des terres modifiée et la contamination. En réponse, les chercheurs canadiens sont devenus des leaders mondiaux dans la caractérisation des impacts des perturbations sur la fonction des milieux humides et ont été à l'avant-garde de techniques innovantes de restauration et de remise en état. À mesure que la valeur des milieux humides est de plus en plus reconnue par les parties prenantes et les décideurs, le besoin de recherche sur les milieux humides basée sur des preuves ne fera que croître. Les chercheurs canadiens sont bien positionnés pour continuer à diriger la recherche en hydrologie des milieux humides au cours des 75 prochaines années. [ABSTRACT FROM AUTHOR]

We conducted a 2‐year study to examine the impacts of resource access roads on carbon (C) exchange in two forested boreal peatlands (a bog and a fen). Along six transects (perpendicular to the road), at 2, 6, and 20 m from the edge of the road on both sides of the road (RI areas), we measured understory CO2 fluxes bi‐weekly from May to August 2016 and 2017 and compared this to measurements at reference areas at least 50 m from the road. Furthermore, we estimated aboveground biomass and net primary productivity of overstory shrubs and trees and combined that with understory fluxes to estimate annual net ecosystem carbon balance, and road‐induced C emissions. Overall, at the bog, the RI areas were sources of C in both 2016 (89.9 g C m−2 y−1) and 2017 (108.9 g C m−2 y−1) while reference areas were sinks. However, at the fen, both RI areas (−744.7, −310.9 g C m−2 y−1 in 2016 and 2017, respectively) and reference areas were sinks of C. Averaged across both peatlands, the estimated road‐induced C losses were ∼7.97 and 7.40 Mg C for each km of the road in 2016 and 2017, respectively. However, areas connected by culverts showed lower road‐associated impact on C emissions. Therefore, we suggest that industries and infrastructure developers align the road parallel to the local water flow direction, when possible, consider the hydrogeological setting during road design to reduce hydrologic impacts, and increase hydrological flows between up‐ and downstream by adequate culverts. Plain Language Summary: The boreal region of Canada has significant numbers of resource access roads passing through peatlands. Undisturbed peatlands are globally important reservoirs of carbon (C, a component of carbon dioxide i.e., associated with global warming). In this study, we determined the impacts of resource access roads in two boreal forested peatlands (a bog and a fen) on C dynamics from the adjacent peatland. Our results showed that, at the bog, the road impacted areas were sources of carbon in both study years. However, in both study years, the fen was a sink of C. At both sites, the road‐impacted areas had less C uptake than undisturbed areas and this was caused by both the road affecting the wetness of the peatland and due to clearing of shrubs and trees adjacent to the road. Our study estimated road induced C losses were ∼7,970 and 7,400 kg C for each km of the road in 2016 and 2017, respectively. This study will help industries and infrastructure developers improve road construction design by considering the hydrogeological setting to reduce hydrologic impacts and increase hydrological flows between upstream and downstream areas through adequate culverts. Key Points: Access roads crossings peatlands alter carbon dynamics by disturbing local hydrology and vegetation coverEach kilometer of the road emitted a significant amount of carbon (∼7.97 and 7.40 Mg C in 2016 and 2017, respectively)To minimize road‐associated impacts, the road design should be aimed to minimize the road's hydrologic impact [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]

Peatland degradation due to human activities is contributing to rising atmospheric CO2 levels. Restoring the carbon (C) sink function in degraded peatlands and preventing further stored C losses is a key climate mitigation strategy, given the global scale of peatland disturbance. Active restoration involving a combination of rewetting and vegetation reestablishment at a post‐extraction peatland in Canada has been shown to successfully re‐establish net CO2 uptake rates similar to undisturbed peatlands within a decade or two. However, lower than expected CH4 emissions suggest recovery of belowground C cycling processes may lag behind the recovery of the surface net flux. Using closed chamber measurements over a warm season, we determined that restored Sphagnum, which covers two thirds of the site, was a null source of CH4. Emissions from the restored site were primarily attributed to vascular plant substrate inputs, measured as acetate, and plant‐mediated transport. The C isotopic fractionation factor for CH4 and CO2 in the pore water from the restored former peat field suggested reduced hydrogenotrophic CH4 production deeper in the cutover peat profile (0.8 m depth). In contrast, isotopic fractionation in the former drainage ditches showed a balance of acetoclastic and hydrogenotrophic methanogenesis deeper in the profile, indicative of some bulk peat C turnover. This study suggests that the legacy of substrate quality in the cutover peat can reduce the climate warming impact of newly restored peatlands through a reduction in CH4 production and thus emission. Plain Language Summary: Restoration of degraded peatlands is increasingly being considered a tool to mitigate the global temperature rise associated with climate change. This study is the first to isolate methane production and emission processes to explain why methane release from post‐extraction peatlands restored by a combined rewetting and vegetation reestablishment is lower than that of undisturbed peatlands. Carbon turnover of bulk cutover peat was limited to former ditch areas in the restored peatland, which comprise less than 5% of the site. As a result, methane release from the ecosystem to the atmosphere was low and linked to vascular plant inputs and plant‐mediated transport. This study provides evidence that an active restoration method that restores the water table below the surface and aids reestablishment of Sphagnum can be an effective climate mitigation tool by bringing back endemic vegetation more quickly and avoiding large methane release often associated with unmanaged rewetting. Key Points: Restored site emissions were attributed to vascular plant‐mediated transport, while restored Sphagnum was a null source of methaneThe carbon isotopic fractionation factor for methane and CO2 indicated very little bulk peat carbon turnover beneath the restored SphagnumActive restoration (rewetting and vegetation re‐establishment) can be an effective climate mitigation strategy avoiding large CH4 release [ABSTRACT FROM AUTHOR]

Boreal peatlands represent a globally important store of carbon, and disturbances such as wildfire can have a negative feedback to the climate. Understanding how carbon exchange and greenhouse gas (GHG) dynamics are impacted after a wildfire is important, especially as boreal peatlands may be vulnerable to changes in wildfire regime under a rapidly changing climate. However, given this vulnerability, there is very little in the literature on the impact such fires have on methane (CH4) emissions. This study investigated the effect of wildfire on CH4 emissions at a boreal fen near Fort McMurray, Alberta, Canada, that was partially burned by the Horse River Wildfire in 2016. We measured CH4 emissions and environmental variables (2017–2018) and CH4 production potential (2018) in two different microform types (hummocks and hollows) across a peat burn severity gradient (unburned (UB), moderately burned (MB), and severely burned (SB)). Results indicated a switch in the typical understanding of boreal peatland CH4 emissions. For example, emissions were significantly lower in the MB and SB hollows in both years compared to UB hollows. Interestingly, across the burned sites, hummocks had higher fluxes in 2017 than hollows at the MB and SB sites. We found typically higher emissions at the UB site where the water table was close to the surface. However, at the burned sites, no relationship was found between CH4 emissions and water table, even under similar hydrological conditions. There was also significantly higher CH4 production potential from the UB site than the burned sites. The reduction in CH4 emissions and production in the hollows at burned sites highlights the sensitivity of hollows to fire, removing labile organic material for potential methanogenesis. The previously demonstrated resistance of hummocks to fire also results in limited impact on CH4 emissions and likely faster recovery to pre-fire rates. Given the potential initial net cooling effect resulting from a reduction in CH4 emissions, it is important that the radiative effect of all GHGs following wildfire across peatlands is taken into account. [ABSTRACT FROM AUTHOR]

Boreal peatlands represent a globally important store of carbon, and disturbances such as wildfire can have a negative feedback to the climate. Understanding how carbon exchange and greenhouse gas (GHG) dynamics are impacted after a wildfire is important, especially as boreal peatlands may be vulnerable to changes in wildfire regime under a rapidly changing climate. Yet, given this vulnerability, there is very little in the literature on the impact such fires have on methane (CH4) emissions. This study investigated the effect of wildfire on CH4 emissions at a boreal fen near Fort McMurray, AB, Canada, that was partially burned by the Horse River Wildfire in 2016. We measured CH4 emissions and environmental variables (2017-2018) and CH4 production potential (2018) in two different microform types (hummocks and hollows) across a burn severity gradient (unburned (UB), moderately burned (MB) and severely burned (SB)). Results indicated a switch in the typical understanding of boreal peatland CH4 emissions. For example, emissions were much lower in the MB and SB hollows in both years compared to UB hollows. Interestingly, across the burned sites, hummocks had higher fluxes in 2017 than hollows at the MB and SB sites. We found typically higher emissions at the UB site where the water table was close to the surface. However, at the burned sites, no relationship was found between CH4 emissions and water table, even under similar hydrological conditions. This further strengthens the argument on the overriding influence of fire. There was also significantly higher CH4 production potential from the UB site than the burned sites. The reduction in CH4 emissions and production in the hollows at burned sites highlights the sensitivity of hollows to fire, removing labile organic material for potential methanogenesis. The previously demonstrated resistance of hummocks to fire also results in limited impact to CH4 emissions and likely faster recovery to pre-fire rates. Given the potential initial net cooling effect resulting from a reduction in CH4 emissions, it is important that the radiative effect of all GHG following wildfire across peatlands is taken into account. [ABSTRACT FROM AUTHOR]

Northern peatlands store globally significant amounts of soil carbon that could be released to the atmosphere under drier conditions induced by climate change. We measured forest floor respiration (RFF) at hummocks and hollows in a treed boreal bog in Alberta, Canada and partitioned the flux into aboveground forest floor autotrophic, belowground forest floor autotrophic, belowground tree respiration, and heterotrophic respiration using a series of clipping and trenching experiments. These fluxes were compared to those measured at sites within the same bog where water-table (WT) was drawn down for 2 and 12 years. Experimental WT drawdown significantly increased RFF with greater increases at hummocks than hollows. Greater RFF was largely driven by increased autotrophic respiration driven by increased growth of trees and shrubs in response to drier conditions; heterotrophic respiration accounted for a declining proportion of RFF with time since drainage. Heterotrophic respiration was increased at hollows, suggesting that soil carbon may be lost from these sites in response to climate change induced drying. Overall, although WT drawdown increased RFF, the substantial contribution of autotrophic respiration to RFF suggests that peat carbon stocks are unlikely to be rapidly destabilized by drying conditions. [ABSTRACT FROM AUTHOR]

Peatlands in the western boreal plains of Canada are important ecosystems as they store over two percent of global terrestrial carbon. However, in recent decades, many of these peatlands have been fragmented by access roads constructed for resource extraction and transportation, challenging their carbon storage potential. To investigate how roads have been impacting tree and shrub growth and productivity in these peatlands, this study was conducted in a forested bog and woody fen in Carmon Creek, Alberta, Canada. In 2017, vegetation surveys were conducted along 20 m transects that extended on both sides of the road with 4 m2 circular plots at 2, 6 and 20 m distance from the road and were followed by disc or core collection from woody stems. Within 20 m of the road at the bog site, we observed a shift towards significantly larger radial growth of trees in the downstream areas (t = 3.23, p = 0.006) where water table position was deeper, while at the fen site, radial growth of tall shrubs had little response to the road. Combining the effects of direct tree clearing and hydrology induced shifts in growth, aboveground net primary productivity (NPPag) post-road construction was reduced significantly in areas where vegetation was cleared during the road construction (i.e., upstream areas of the bog: t = 5.21, p < 0.0001 and downstream areas of the fen: t = 2.64, p = 0.07). Substantially lower NPPag around the road construction areas compared to reference areas shows tremendous loss of carbon sink potential of trees and shrubs after road construction through peatlands. Altogether, roads constructed through peatlands perpendicular to the water flow may shift long-term carbon sinks into sources of carbon, at least for the initial few years following road construction. [ABSTRACT FROM AUTHOR]

Northern peatlands are globally significant soil carbon sinks but contribute a significant amount of dissolved organic carbon (DOC) to streams. Climate change driven warming and drying will likely alter peatland DOC dynamics; however, few field studies have quantified the individual and interactive effects of temperature and moisture changes. Using a full factorial water table (control, drained 2 years [experimental], drained 12 years [drained]) × warming (ambient, open‐top chamber warming) × microform (hummock, hollow) study design, we monitored DOC concentration and spectrophotometric properties (specific ultraviolet absorbance [SUVA], E2/E3, E4/E6) in a wooded boreal bog in Alberta, Canada. Ecohydrological conditions including water table (WT), soil temperature, plant cover, biomass, and productivity were also measured at each plot. We observed a significant interaction between WT treatment, warming and microform for explaining variation in DOC concentrations, with the highest values at drained, warmed hummocks. Overall, drainage resulted in higher DOC concentration. DOC concentration and E2/E3 increased, whereas SUVA decreased, in response to greater plant productivity (i.e., more negative values of gross ecosystem photosynthesis). For DOC concentration and SUVA, this correlation was largely driven by drained, warmed hummocks where shrub growth increased. Moreover, redundancy analysis indicated that shrub and lichen cover, along with WT and soil temperature, were important for explaining variation in DOC concentration and quality. The results indicate that, although DOC concentrations in peatlands are likely to increase under climate change, much of this increase may be from recent carbon fixation, suggesting more rapid carbon cycling as opposed to destabilization of existing carbon stocks. [ABSTRACT FROM AUTHOR]

Peatlands play a significant role in global greenhouse gas (GHG) cycling as they store a significant amount (approx. 550 Gt) of organic carbon in the form of peat. The boreal region of Canada has one of the highest densities of peatlands. However, they have been impacted by various linear disturbances including winter roads, pipelines, seismic lines, oil sand drillings (well-pads), and resource access road construction. A more than 217,000 km long road network has been constructed on the boreal region of Canada to explore and extract natural resources (e.g. oil sands and forestry). Roads on peatlands are raised by placing mineral fill on the compressed peat underneath. Therefore, the road itself acts as a dam and limits the hydrological connection between fragmented parts of the peatland. The resulting hydrological variation may lead to altered GHG emissions, plant community, microbial activity, and soil biogeochemistry in peatlands. However, few studies have quantified the impacts of access roads on boreal peatland carbon dynamics. Therefore, we conducted a study focusing on the impacts of roads on carbon dynamics of a forested bog and a shrubby fen near Peace River, Alberta, Canada. Data was collected in 2016 and 2017 from May to August. The data plots represented three factors: 1) side of the road (upstream and downstream), 2) distance from a culvert (<2 and >20 m), and 3) and distance from either side of the road (2, 6, 20 m). Results from 2016 showed that, overall, the ground layer of the bog was a source (1.66 g CO2 m-2 d-1) and the fen was a sink (-19.06 g CO2 m-2 d-1) of CO2. In 2017, the ground layers of both the bog and fen were sinks of CO2 (-1.35 g CO2 m-2 d-1 and -19.06 g CO2 m-2 d-1, respectively). In general, hydrologic effects of the road were less at the fen due to the orientation of the road relative to the local slope of the peatland. At this site, variation in C fluxes relative the road was also small, but there was an overall reduction in C sink function due to plant community disturbance. At the bog, flooding occurred on the upstream side of the road. This was more severe far from culverts and close to the road. When culverts were in place, water was moved across the road, but wet conditions were created on the downstream side due to concentration flow. This resulted in higher CH4 emissions close to the road and reduced CO2 uptake so that the area near the road had a greatly reduced C and GHG sink function than undisturbed areas, even when culverts were present.However, the carbon flux varied depending on the side of the road, distance from the road, and the distance from the culvert. In our presentation, we will present the main findings of our study and show how resource roads have the potential to alter the carbon dynamics of peatlands. Also, we will recommend measures how the road associated impacts could be minimized. [ABSTRACT FROM AUTHOR]

Recently, fen construction projects on surface mines in northeastern Alberta have been attempted as a reclamation strategy to reintroduce peatlands into the region where industry disturbs a substantial amount of wetland ecosystems. Knowledge of carbon cycling and greenhouse gas (GHG) dynamics, including methane (CH 4 ), is one way to understand the biogeochemical function of newly constructed fen ecosystems. In this study we monitored CH 4 emissions and CH 4 pore water concentration, as well as ecological and soil chemistry controls on CH 4 emissions and pore water concentration, from a constructed fen. The same variables were also monitored at two natural reference fens that had similar vascular vegetation to the constructed fen. Methane emissions were lower at the constructed fen compared to the reference poor fen, but similar to the reference saline fen. However, CH 4 concentration in pore water at 0.2 m and 0.7 m depth was lower at the constructed fen than either of the natural reference sites. The supply rate of sulfur (all mobile forms) was the most dominant control on CH 4 emission and CH 4 pore water concentration. While low CH 4 emissions may be beneficial for constructed fens from a GHG perspective, this condition indicates that peat and carbon accumulation at these reclaimed sites may ensue slowly. Therefore, a clear statement of goals is required to determine how CH 4 dynamics from constructed fen ecosystems relate to the reclamation outcome. [ABSTRACT FROM AUTHOR]

Boreal peatlands represent a globally important store of carbon, and disturbances such aswildfire can have a significant positive feedback to the climate. Understanding how carboncycling and greenhouse gas (GHG) dynamics are impacted after a wildfire is important,especially as boreal peatlands may be vulnerable to changes in wildfire regime under arapidly changing climate. Yet given this vulnerability, there is very little in the literature onthe impact such fires have on methane (CH4) emissions. This study investigated the effect of wildfire on CH4 emissions at a boreal fen near FortMcMurray, AB, Canada, partially burned by the Horse River Wildfire in 2016. We measuredCH4 emissions and environmental variables (2017-2018) and CH4 production potential(2018) in two different microform types (hummocks and hollows) across a burnseverity gradient (unburned (UB), moderately burned (MB) and severely burned(SB)). The average CH4 flux at the UB hollows was 96.5 and 66.6 mg CH4 m−2 d−1in 2017 and2018, respectively. Methane emissions were much lower in the MB and SB hollows in bothyears, with the average flux being 0.25 and 0.06 mg CH4 m−2d−1 in 2017 and 1.93 and 1.38mg CH4m−2 d−1, respectively. Interestingly, across the burned sites, hummocks had higherfluxes in 2017 than hollows with the average flux being 1.82 and 5.83 mg CH4m−2 d−1 at theMB and SB sites, respectively. Results of a linear mixed effects model (LMM) illustrate thereis a significant effect of burn severity on CH4 flux, although no significant difference betweenmicroform or year. Another LMM found a significant interaction between burnseverity and both soil temperature at 30 cm depth and water table. There was alsosignificantly higher CH4 production potential from the UB site than the burnedsites. The reduction in CH4 emissions and production in the hollows at burned sites highlightsthe sensitivity of hollows to fire, removing labile organic material for potentialmethanogenesis. The previously demonstrated resilience of hummocks to fire also results inlimited impact to methane emissions and likely faster recovery to pre-fire rates. [ABSTRACT FROM AUTHOR]

The moss layer transfer technique has been developed to restore the carbon sequestration function and typical vegetation of Sphagnum-dominated peatlands after peat extraction in North America. However, the technique does not lead to successful bryophyte establishment when applied to peatlands with a richer residual fen peat. Therefore, we evaluated an alternative method of active rewetting and passive vegetation establishment using vegetation surveys and carbon dioxide and methane (CH 4 ) flux measurements at a post-extracted fen in southern Manitoba, Canada. After one growing season post-rewetting, wetland vegetation established and the site was a net carbon sink over the growing season. However, high abundance of Carex lasiocarpa 10 years post-treatment led to higher CH 4 emissions than the reference ecosystem. Successful establishment of wetland vegetation is attributed to the area being surrounded by undisturbed fens that can provide a local source of plant propagules. Bryophyte expansion was less successful than vascular plants, likely due to episodic flooding and shading from the sedge communities. Therefore, careful management of water levels to just below the peat surface is needed if reference vegetation community recovery is the goal of restoration. Water level management will also play a key role in controlling CH 4 emissions to maximize carbon sequestration potential., (© 2023. The Author(s).)

Peatlands after drainage and extraction are large sources of carbon (C) to the atmosphere. Restoration, through re-wetting and revegetation, aims to return the C sink function by re-establishing conditions similar to that of an undrained peatland. However, the time needed to re-establish C sequestration is not well constrained due to the lack of multi-year measurements. We measured over 3 years the net ecosystem exchange of CO 2 (NEE), methane ( F CH 4 ), and dissolved organic carbon (DOC) at a restored post-extraction peatland (RES) in southeast Canada (restored 14 years prior to the start of the study) and compared our observations to the C balance of an intact reference peatland (REF) that has a long-term continuous flux record and is in the same climate zone. Small but significant differences in winter respiration driven by temperature were mainly responsible for differences in cumulative NEE between years. Low growing season inter-annual variability was linked to constancy of the initial spring water table position, controlled by the blocked drainage ditches and the presence of water storage structures (bunds and pools). Half-hour F CH 4 at RES was small except when Typha latifolia-invaded drainage ditches were in the tower footprint; this effect at the ecosystem level was small as ditches represent a minor fraction of RES. The restored peatland was an annual sink for CO 2 (-90 ± 18 g C m -2  year -1 ), a source of CH 4 (4.4 ± 0.2 g C m -2  year -1 ), and a source of DOC (6.9 ± 2.2 g C m -2  year -1 ), resulting in mean net ecosystem uptake of 78 ± 17 g C m -2  year -1 . Annual NEE at RES was most similar to wetter, more productive years at REF. Integrating structures to increase water retention, alongside re-establishing key species, have been effective at re-establishing the net C sink rate to that of an intact peatland., (© 2018 John Wiley & Sons Ltd.)