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Horticultural peat harvesting is expanding in Canada with the potential to negatively impact downstream water quality. Previous studies have reported variable responses in outflow nitrogen (N) and phosphorus (P) concentrations associated with peat harvesting operations, which may be due to unaccounted differences in biogeoclimatic setting or harvesting phase. Within a given peatland, major changes occur to its hydrological and physicochemical properties as it transitions through sequential harvesting phases: from a natural peatland, to an extraction field, and finally to a restored peatland. The linkage between hydrology and nutrient export, and the impact on water quality associated with each phase, have not been studied in relation to geology, relief, and climate across the Canadian boreal. This knowledge is crucial to account for the variability in exported nutrient concentrations, accurately determine the relative risk to downstream waterways, and direct best management practices. The objective of this study was to understand the linkages between peatland hydrological connectivity, ditch substrate, and peat harvesting phase on nutrient mobility at two peatlands in the sub-humid, glaciated, boreal region in Alberta, Canada. Water level, volumetric flow rate, ice and aeration depth, electrical conductivity (EC) and pH were measured at natural, newly opened, extracted, and restored peatlands. Chemical analyses of dissolved and particulate N and P were assessed in surface water, groundwater, and at outflow locations approximately once per month from March through October in 2019 and 2021. In situ ion availability was measured in surface peat layers, alongside surface and below ground temperature, soil moisture, and peat aeration in 2021. Compared to natural peatland areas, the results show that harvesting activities greatly decreased natural water storage capacity, encouraged ice formation, and increased spring runoff in a summer runoff dominated landscape. Drainage ditches further increased hydrological connectivity and outflow from extracted peatlands throughout the year. When ditches reached underlying mineral sediments, EC and pH values differed drastically from natural peatland drainage waters. The effect of extraction and ditching on in situ moisture and aeration in extracted surface layers was minimal compared to the natural peatland, despite lowered water tables. In contrast, N and P values varied drastically between the three harvest phases. During extraction, surface peat had elevated ammonium and nitrate availability compared to natural and restored peatlands. Nitrate remained available in the surface peat throughout the year; however, exports were only detected at the outflow when the peat fields were frozen or following large rainfall events. Nitrate was not detected if the hydrological connectivity between the peat field and its outflow was severed. Extracted and restored peatlands had elevated particulate P at field outflow locations compared to natural sites, likely from ditch clearing or loose peat in the process of settling. Clearly, ditch substrate has a major influence on water quality. Further, hydrological connectivity differs with each harvest phase, resulting in contrasting nutrient transformations and export that will continue to evolve as additional peat fields are opened, extracted, and restored.

Significance Peatlands are sensitive ecosystems that store carbon and water and support biodiversity. Currently, European peatlands are threatened by climate change and exploitation. In this study, we show that many landscape settings may support both wetland ecosystems on thick peat soils and forest ecosystems on thin organic soils. Both ecosystems have distinctly different water–carbon dynamics that create internal positive feedbacks, allowing both ecosystems to coexist (bistability) but also to shift when critical limits are exceeded. With this new landscape perspective, we find that currently, 20% of European raised bogs are threatened by climate change and drainage. This study demonstrates that a landscape perspective including interactions between peatlands, forests, and rivers is essential to understand and steer the future of peatlands., Northern peatlands store large amounts of carbon. Observations indicate that forests and peatlands in northern biomes can be alternative stable states for a range of landscape settings. Climatic and hydrological changes may reduce the resilience of peatlands and forests, induce persistent shifts between these states, and release the carbon stored in peatlands. Here, we present a dynamic simulation model constrained and validated by a wide set of observations to quantify how feedbacks in water and carbon cycling control resilience of both peatlands and forests in northern landscapes. Our results show that 34% of Europe (area) has a climate that can currently sustain existing rainwater-fed peatlands (raised bogs). However, raised bog initiation and restoration by water conservation measures after the original peat soil has disappeared is only possible in 10% of Europe where the climate allows raised bogs to initiate and outcompete forests. Moreover, in another 10% of Europe, existing raised bogs (concerning ∼20% of the European raised bogs) are already affected by ongoing climate change. Here, forests may overgrow peatlands, which could potentially release in the order of 4% (∼24 Pg carbon) of the European soil organic carbon pool. Our study demonstrates quantitatively that preserving and restoring peatlands requires looking beyond peatland-specific processes and taking into account wider landscape-scale feedbacks with forest ecosystems.

Initiation of wetland features is integral to sustaining landscape eco-hydrological function and meeting defined goals in surface mine reclamation. Within the sub humid climate of the Athabasca Oil Sands, Canada, the water generation mechanisms (external water sources, internal feedback mechanisms) that enable wetlands to form opportunistically on recently reconstructed landscapes are currently unknown, restricting the flexibility in mine closure planning. To address this knowledge gap, we interpret site and local physical characteristics of opportunistic wetlands within the Athabasca Oil Sands through a synoptic survey. Wetlands formed in ~ 8% of the random survey transect areas designed and planted for forestlands. Wetlands had vegetation structures characteristic of woody Salix spp. swamps and narrow-leaved Carex spp. marsh wetland types, with minor coverage of open water marshes. Wetlands formed opportunistically over a range of slopes, aspects and topographic positions, across contrasting fine and coarse-textured landforms. However, different wetland establishment and maintenance controls exist on fine and coarse-textured landforms. On coarse-textured landforms with large groundwater transmissivity, wetland formation was influenced by landscape-scale factors; wetlands were restricted to the toes of slopes and areas intersecting groundwater. On fine-textured constructed landforms, small and large wetlands occurred on lower landscape elevations with the potential for the external (cumulative) water sources, and in hydrologically isolated locations with little potential for runoff contribution from adjacent forestlands (saturation and wetland formation through internal feedback mechanisms). Regardless of landscape position, wetlands formed on flat areas and in shallow inward draining endorheic pans with clay rich soils where low water storage potential promotes frequent surface saturation. These findings have important implications in landscape reclamation design, suggesting that passive techniques that support internal feedback mechanisms may offer a more cost effective reclamation approach compared to more active, expensive techniques that aim to develop wetlands with external water sources.

River temperature is well established as an important variable for aquatic denizens. Given its importance, researchers are attempting to disentangle complex interactions between landscapes and river temperatures. We investigated how landscape variables of geomorphology, geology, and vegetation can explain a large portion of the spatial variations amongst tributary temperatures in the large, Miramichi watershed, New Brunswick. We utilize thermal infrared imagery (TIR) to characterize river temperature and remote sensed data to delineate landscape variables. Partial Least Squares regression (PLS) models indicated that variability in river temperature was associated with landscape attributes, but these differed with physiography. For the Clearwater Brook and Burnthill Brook watersheds located on the Miramichi Highlands physiographic unit, solar radiation exposure, surficial geology deposit (comprising gravels, sands, and minor silt), geological contact zones, and maximum watershed slope were strongly and positively correlated with river temperature. We stipulate that the interaction of slope steepness and geologic contact zones can produce complex local and larger groundwater interactions influencing river temperatures in this physiographic region. In the lower elevation, and lower relief, Cains River watershed, located on the Maritime Plains physiographic unit, watershed elevation and wetlands were significant and positively correlated with river temperatures. Here the main stem was cooler in the downstream reaches, likely due to the semi-confined channel interaction with groundwater discharge originating from the surficial deposits and fractured underlying sandstone of the lowlands, and possibly hyporheic processes. These findings illustrate how physiography and geomorphology influence thermal processes in flowing waters at both the landscape and local scales, and the resultant implications for management and conservation efforts both in terms of land use and climate change.

The potential of high severity wildfires to increase global terrestrial carbon emissions and exacerbate future climatic warming is of international concern. Nowhere is this more prevalent than within high latitude regions where peatlands have, over millennia, accumulated legacy carbon stocks comparable to all human CO2 emissions since the beginning of the industrial revolution. Drying increases rates of peat decomposition and associated atmospheric and aquatic carbon emissions. The degree to which severe wildfires enhance drying under future climates and induce instability in peatland ecological communities and carbon stocks is unknown. Here we show that high burn severities increased post-fire evapotranspiration by 410% within a feather moss peatland by burning through the protective capping layer that restricts evaporative drying in response to low severity burns. High burn severities projected under future climates will therefore leave peatlands that dominate dry sub-humid regions across the boreal, on the edge of their climatic envelopes, more vulnerable to intense post-fire drying, inducing high rates of carbon loss to the atmosphere that amplify the direct combustion emissions.

The capability of peatland ecosystems to regulate evapotranspiration (ET) following wildfire is a key control on the resilience of their globally important carbon stocks under future climatic conditions. Evaporation dominates post‐fire ET, with canopy and sub‐canopy removal restricting transpiration and increasing evaporation potential. Therefore, in order to project the hydrology and associated stability of peatlands to a diverse range of post‐fire weather conditions and future climates the regulation of evaporation must be accurately parameterised in peatland ecohydrological models. To achieve this, we measure the surface resistance (rₛ) to evaporation over the growing season one year post‐fire within four zones of a boreal peatland that burned to differing depths, relating rₛ to near surface soil tensions. We show that the magnitude and temporal variability in rₛ varies with burn severity. At the peatland scale, rₛ and near‐surface tension correlates non‐linearly. However, at the point scale no relationship was evident between temporal variations in rₛ and near‐surface tension across all burn severities; in part due to the limited fluctuation in near‐surface tensions and the precision of rₛ measurements. Where automated measurements enabled averaging of errors, the relationship between near‐surface tension and rₛ switched between periods of strong and weak correlation within a burned peat hummock. This relationship, when strong, deviated from that obtained under steady state laboratory conditions; increases in rₛ were more sensitive to fluctuations in near‐surface tension under dynamic field conditions. Calculating soil vapour densities directly from near‐surface tensions is shown to require calibration between peat types and provides little if any benefit beyond the derivation of empirical relationships between rₛ and measured soil tension. Thus, we demonstrate important spatiotemporal fluctuations in post‐fire rₛ that will be key to regulating post‐fire peatland hydrology, but highlight the complex challenges in effectively parameterising this important underlying control of near‐surface tensions within hydrological simulations.

Sphagnum moss and age-dated peat cores from bogs have long been used to study contemporary and past atmospheric deposition of trace elements (TEs). However, other components of bog ecosystems represent additional scientific opportunities. Snowpack sampling, for example, represents a chance to study winter deposition while providing the perfect matrix for ICP-MS analyses of TEs. The berries that grow in bogs, including blueberry (Vaccinium myrtilloides), cloudberry (Rubus chaemomorus), cranberry (Vaccinium oxycoccus) and lingonberry (Vaccinium vitisidaea), provide insight into the bioavailability of micronutrients (and contaminants) at the surface of the bog, as well as an index of dust deposition onto the fruits themselves. Labrador Tea (Rhododendron groenlandicum) provides similar information, but with greater relevance for Indigenous Peoples, as this is an important medicinal plant for them, along with the Pitcher Plant (Sarracenia purpurea). The acidic, organic-rich waters which represent > 90 % of the mass of these ecosystems, presents an even greater opportunity: the chance to quantify the extent to which aerosols and dusts dissolve, subsequent to deposition from the air. In this study, we present data for TEs in all of these media, with a view to exploring the broader potential of ombrotrophic peatlands as natural, holistic, integrated, long-term monitoring systems. The approach presented here not only addresses our need for information regarding atmospheric deposition of environmental contaminants to terrestrial ecoystems, but also insight into their release, or potential release, to downstream aquatic ecosystems.

Wetlands have and continue to undergo rapid environmental and anthropogenic modification and change to their extent, condition, and therefore, ecosystem services. In this first part of a two-part review, we provide decision-makers with an overview on the use of remote sensing technologies for the ‘wise use of wetlands’, following Ramsar Convention protocols. The objectives of this review are to provide: (1) a synthesis of the history of remote sensing of wetlands, (2) a feasibility study to quantify the accuracy of remotely sensed data products when compared with field data based on 286 comparisons found in the literature from 209 articles, (3) recommendations for best approaches based on case studies, and (4) a decision tree to assist users and policymakers at numerous governmental levels and industrial agencies to identify optimal remote sensing approaches based on needs, feasibility, and cost. We argue that in order for remote sensing approaches to be adopted by wetland scientists, land-use managers, and policymakers, there is a need for greater understanding of the use of remote sensing for wetland inventory, condition, and underlying processes at scales relevant for management and policy decisions. The literature review focuses on boreal wetlands primarily from a Canadian perspective, but the results are broadly applicable to policymakers and wetland scientists globally, providing knowledge on how to best incorporate remotely sensed data into their monitoring and measurement procedures. This is the first review quantifying the accuracy and feasibility of remotely sensed data and data combinations needed for monitoring and assessment. These include, baseline classification for wetland inventory, monitoring through time, and prediction of ecosystem processes from individual wetlands to a national scale.

A widely accepted approach in both conceptual and numerical models of groundwater flow is to assume that the water table (WT) is a subdued replica of topography, where groundwater recharges at topographic highs and discharges at topographic lows. However, WTs in low-relief, water-limited environments are generally not topographically controlled, therefore traditional paradigms where forested hummocks are sources of water to both adjacent local wetland-pond systems and catchment-scale runoff do not usually hold true. Local groundwater flow systems (flow in which the recharge area is directly adjacent to its discharge area) are necessary to link forested hummocks with adjacent peatlands or ponds. However, the development of the groundwater mounds beneath topographic highs required to generate local groundwater flow systems is both spatially and temporally infrequent in low-recharge settings like the Boreal Plains. Thus, identifying the spatiotemporal controls on groundwater mounding is crucial to understanding the climatic and geological conditions required for landscape connectivity and runoff generation at larger, regional scales. This insight is becoming increasingly important as water security, ecosystem sustainability, and environmental quality become the focus of land management and reclamation efforts.The Canadian Boreal Plains are dominated by aspen mixedwood forests, shallow lakes, and peatlands, and has a sub-humid climate that causes large interannual variability in runoff generation and hydrological connectivity at the landscape scale. Through a combination of field observations and numerical modelling, this study identifies the role of aspen forested hummocks in the generation (or loss) of groundwater and hydrologic connectivity to adjacent peatlands and lakes. WT elevations and climate data (precipitation (P) and potential evapotranspiration (PET)) collected over the last 20 years at nine fine-textured forested hummocks were examined for frequency and magnitude of groundwater mounding and/or depressions relative to their adjacent peatlands. It was evident that no simple metric (e.g., annual P, multiyear cumulative P-PET, etc.) was a good predictor for WT position. Through a combination of 1D and 2D, variably saturated numerical modelling, we identify the relative spatiotemporal controls that hummock morphometry, texture, and climate have on groundwater recharge and WT position. Multiple scales of climate forcings (seasonal, interannual; P, PET), substrate texture, hummock height, and rooting parameters all affect groundwater recharge (both positive and negative). Groundwater recharge is most dependent on timing and magnitude of snow melt; however, during periods of large interannual moisture surplus, when available subsurface storage is low, large summer and fall storms can also contribute to recharge. Otherwise, the overwhelming majority of scenarios result in hummocks storing and transpiring water and receiving inputs of groundwater from neighboring peatlands, therefore acting as a net sink of water to the larger landscape.We show that groundwater mounds, and therfore the development of local topographic flow systems, under forested hummocks are spatiotemporally rare in sub-humid, low-relief regions, resulting in these hummocks being net sinks of water. Not only does this study emphasize the role of peatlands in the generation of landscape-scale runoff, it encourages a reconceptualiztion of the overall hydrologic function of forestlands and peatlands in catchment hydrology.

Groundwater table depth and peat moisture, exert a first order control on a range of biogeochemical and -physical peatland processes, and the susceptibility to peat fires. Therefore, one of the first critical measures to identify “peatlands under pressure” is the change of hydrological conditions, e.g. due to changing climatic conditions or direct “hydraulic” human influence. In this presentation, we introduce a new opportunity for the global-scale monitoring of moisture conditions in peatlands. We assimilate L-band brightness temperature (Tb) data from the Soil Moisture Ocean Salinity (SMOS) into the Catchment land surface model (CLSM) to improve the simulation of Northern peatland hydrology from 2010 through 2019. We compare four simulation experiments: two open loop and two data assimilation simulations, either using the default CLSM or a recently-developed peatland-specific adaptation of it (PEATCLSM, Bechtold et al. 2019). The assimilation system uses a spatially distributed ensemble Kalman filter to update soil moisture and groundwater table depth. The simulation experiments are evaluated against an in-situ dataset of groundwater table depth in about 20 natural and semi-natural peatlands that are large enough to be dominant in the corresponding 81-km2 model grid cells. For PEATCLSM, Tb data assimilation increases the temporal Pearson correlation (R) and anomaly correlation (aR) between simulated and measured groundwater table from 0.53 and 0.38 (open-loop) to 0.58 and 0.45 (analysis), respectively. Time series comparison at monitoring sites demonstrates how the assimilation effectively corrects for remaining deficiencies in model physics and/or errors of the global meteorological data forcing the model. The generally lower coefficients of 0.30 (R) and 0.09 (aR) for the default CLSM also improve after Tb data assimilation to values of 0.39 (R) and 0.28 (aR). However, even with Tb data assimilation, the skill of CLSM remains inferior to that of PEATCLSM. The more realistic model physics of PEATCLSM are also supported by a reduction of the Tb misfits (observed Tb – forecasted Tb) over 94 % of the Northern peatland area. The temporal variance of Tb misfits is reduced by 20 % on average and is largest over the large peatland areas of the Western Siberian (25 %) and Hudson Bay Lowlands (40 %). This study demonstrates, for the first time, an improved estimation of the peatland hydrological dynamics by the assimilation of SMOS L-band brightness data into a global land surface model and suggests a new route of research focusing on the incorporation of additional satellite observations into peatland-specific modeling schemes.Bechtold, M., De Lannoy, G.J M., Koster, R.D., Reichle, R.H., et al. (2019). PEAT-CLSM: A Specific Treatment of Peatland Hydrology in the NASA Catchment Land Surface Model. JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS, 11 (7), 2130-2162. doi: 10.1029/2018MS001574.

Peatlands are integral to sustaining landscape eco-hydrological function in water-limited boreal landscapes and serve as important water sources for headwater streams and surrounding forests, and recently for mega-scale watershed construction associated with resource extraction. Despite the regional moisture deficit of the Boreal plains, peatlands and margin swamps exist on topographic highs where low permeability (clogging) layers occur proximal to the surface and are apparently isolated from surface water and local and regional groundwater inputs. The water generating mechanisms (external water sources, internal feedback mechanisms) that enable peatland formation with such delicate water balances in these unique hydrogeologic settings are not well known, and have large implications for understanding the eco-hydrologic role of natural peatlands as well as direct peatland construction in drier boreal landscapes.A multi-year sampling campaign was conducted to collect hydrometric, geochemical (DOC, pH, major cations and anions), and isotopic (D/H, 18O/16O) data from a small isolated peatland-margin swamp complex. We explored the relative roles of margin swamps in buffering water loss and generating perched groundwater, shading and wind protection from adjacent forests, snow redistribution in and around the peatland, and wetland feedbacks on maintenance of peatland moisture and ecosystem function. Long-term (18 year) records of water table gradients between the peatland and an adjacent forest combined with 3 year high intensity water balance calculations show the peatland to be a source of water to adjacent forests during this period and illustrate the dominance of autogenic wetland feedbacks over allogenic controls (external sources) in peatland development at this location. Contrasts in water storage due to the morphometry of the clogging layer appear to the dominant determinants of peatland and swamp form and function. Layers of decomposed peat and fine textured mineral soils in margin swamps with low water storage potential promoted frequent soil saturation and anoxia, limiting forest vegetation growth and water uptake, further enhancing wetland vegetation, water conservation and generation within the wetland complex. Shading and wind protection from adjacent forests appear to influence soil frost duration and atmospheric demand to further reduce evapotranspiration losses contributing to a slight moisture surplus in the wetland complex relative to the adjacent forest. Understanding the water balance and moisture surplus controls in isolated peatlands sheds light on the relative role of allogenic and autogenic controls on peatlands with implications for: 1) assessing regional eco-hydrological roles of peatland and forestland covers, 2) predicting landscape-scale response to environmental change and land use, and 3) directing landscape scale reclamation or large reconstruction projects over a range of geologic settings in water-limited boreal regions.

This study examined the hydrological impact of harvesting aspen (Populus tremuloides) within the subhumid Boreal Plains of Alberta, Canada, following clear‐cutting of two stands in successive winters within a small catchment situated in glacial moraine. Impacts were evaluated using a combination of observational data collected from within the harvested catchment and an adjacent reference catchment and numerical simulations conducted with HydroGeoSphere. Sensitivity simulations evaluated the influence of post‐harvest evapotranspiration rates and variability in atmospheric conditions on the range of hydrologic response. Study results indicate that aspen harvesting had limited impact on groundwater levels and streamflows within these hydrologic systems because of the subhumid climate with low frequency of large storms, large soil‐moisture storage capacity of heterogeneous glacial materials, and high evapotranspiration rates of regenerating aspen. Despite an estimated increase in hillslope groundwater levels of up to 3 m, pond and peatland water levels increased by less than 0.3 m and were accompanied by increased streamflows of less than 10 mm. However, predicted increases in groundwater levels and streamflows were sensitive to regenerating aspen evapotranspiration rates, which can be enhanced by appropriate harvesting techniques but may be reduced by climate change. These results are consistent with previous results from within the Boreal Plains but differ from aspen harvesting studies conducted in other settings where appreciable increases in streamflows have been reported. This disparity highlights the need to consider the integrated response of the hydrologic system when evaluating impacts from disturbance and making comparisons between settings.

We use two-dimensional numerical models to identify controls on groundwater recharge, water table dynamics, and the sink-source function of fine-textured hummocks in water-limited environments. A silty clay loam hummock with aspen forest cover in the sub-humid Boreal Plains region of Canada is used to develop a conceptual model and calibrate a variably-saturated flow model to better investigate the dynamics of recharge, water table position, and lateral flow between the forested hummock and adjacent peatland. Scenario testing (achieved by raising and lowering the hydraulic conductivity by an order of magnitude and altering the hummock height and length) provides further understanding of the controls that hydraulic conductivity and hummock morphometry exert on recharge and forestland-peatland interactions. We find that the hydraulic conductivity of the glacial till has the largest control over recharge, followed by the hummock height and length and, lastly, annual atmospheric fluxes. Hummocks with higher hydraulic conductivity or long morphometric profiles are most often sinks of water as they promote increased root-water uptake, while taller hummocks with lower hydraulic conductivity tend to act as hydrologic sources for adjacent wetlands. The magnitude of annual recharge and water table elevation are poorly correlated with annual atmospheric fluxes due to the strong effects of multi-year storage deficits or surpluses; however, they are appreciably affected by decadal wet-dry cycles typical of the Boreal Plains climate. Additionally, we show that both distance along a hummock and elevation are key factors in controlling the spatial distribution of recharge at a single hummock. It is common to conceptualize the water table as a shallow and subdued replica of surface topography, where water flows from topographic highs (i.e., forestlands) to topographic lows (i.e., peatlands) in humid environments; however, as we show here, recharge rates, water table elevation, and the sink-source function of a forested hummock in water-limited environments is highly variable in time and space, and strongly dependent on both the hydrogeological and morphometric properties of the hummock.

Wildfire is the largest disturbance affecting peatlands, with northern peat reserves expected to become more vulnerable to wildfire as climate change enhances the length and severity of the fire season. Recent research suggests that high water table positions after wildfire are critical to limit atmospheric carbon losses and enable the re-establishment of keystone peatland mosses (i.e. Sphagnum). Post-fire recovery of the moss surface in Sphagnum-feathermoss peatlands, however, has been shown to be limited where moss type and burn severity interact to result in a water repellent surface. While in situ measurements of moss water repellency in peatlands have been shown to be greater for feathermoss in both a burned and unburned state in comparison to Sphagnum moss, it is difficult to separate the effect of water content from species. Consequently, we carried out a laboratory based drying experiment where we compared the water repellency of two dominant peatland moss species, Sphagnum and feathermoss, for several burn severity classes including unburned samples. The results suggest that water repellency in moss is primarily controlled by water content, where a sharp threshold exists at gravimetric water contents (GWC) lower than ∼1.4 g g−1. While GWC is shown to be a strong predictor of water repellency, the effect is enhanced by burning. Based on soil water retention curves, we suggest that it is highly unlikely that Sphagnum will exhibit strong hydrophobic conditions under field conditions.

Open pit mining of the Athabasca Bituminous Sands (ABS) generates considerable quantities of mineral dusts, but there is no published record of the amount of material deposited in the surrounding environment via the atmosphere since industry began in 1967. Contemporary as well as past rates of atmospheric dust deposition were reconstructed using age-dated peat cores (210Pb and 14C) collected from five bogs in the vicinity of mines and upgraders and from two bogs far removed from industrial activities. The main objective of this study was to quantify the impact of industry on dust emissions and to do this, the variation in natural “background” rates of mineral matter accumulation also had to be determined. A second objective was to characterize the size, mineralogical composition, and morphology of the particulate matter emitted, to better understand potential environmental consequences of dust emissions. The concentrations of acid insoluble ash (AIA) and Th (a surrogate for insoluble mineral matter) were determined to calculate dust accumulation rates. Scanning electron microscopy with energy dispersive x-ray analysis failed to reveal much variation in mineralogical composition, but near industry the size of the particles was more variable. The abundance of fly ash particles increased with depth which suggests that emissions from upgrader stacks may have declined over time. A comparison of AIA inventories with the pH of the porewaters suggest that the acid-soluble ash fraction of the dusts deposited may have impacted the chemical composition of the bog waters.

Northern peatlands are a vital component of the global carbon cycle, containing large stores of soil organic carbon and acting as a long-term carbon sink. Moss productivity is an important factor in determining whether these wetlands will retain this function under future climatic conditions. Research on unsaturated water flow in peatlands, which controls moss productivity during periods of evaporative stress, has focused on relatively deep bog systems. However, shallower peatlands and marginal connective wetlands can be essential components of many landscape mosaics. In order to better understand factors influencing moss productivity, water balance simulations using Hydrus 1-D were run for different soil profile depths, compositions and antecedent moisture conditions. Our results demonstrate a bimodal distribution of peatland realizations; either primarily conserving water by limiting evapotranspiration or, maximizing moss productivity. For sustained periods of evaporative stress, both deep water storage and a shallow initial water table delay the onset of high vegetative stress, thus maximizing moss productivity. A total depth of sand and peat of 0.8 m is identified as the threshold above which increasing peat depth has no effect on changing vegetative stress response. In contrast, wetlands with shallow peat deposits (less than 0.5 m thick) are least able to buffer prolonged periods of evaporation due to limited labile water storage, and will thus quickly experience vegetative stress and so limit evaporation and conserve water. With a predicted increase in the frequency and size of rain events in continental North America the moss productivity of shallow wetland systems may increase, but also greater moisture availability will increase the likelihood they remain as wetlands in a changing climate.

Boreal peatlands may be vulnerable to projected changes in the wildfire regime under future climates. Extreme drying during the sensitive post-fire period may exceed peatland ecohydrological resilience, triggering long-term degradation of these globally significant carbon stocks. Despite these concerns, we show low peatland evapotranspiration at both the plot and landscape scale post-fire, in water-limited peatlands dominated by feather moss that are ubiquitous across continental western Canada. Low post-fire evapotranspiration enhance the resilience of carbon stocks in such peatlands to wildfire disturbance and reinforces their function as a regional source or water. Near-surface water repellency may provide an important, previously unexplored, regulator of peatland evapotranspiration that can induce low evapotranspiration in the initial post-fire years by restricting the supply of water to the peat surface.

The legacy propagule banks of salvaged topsoils are excellent sources of plant propagules for reclamation of mine sites; however, earlier studies show that less than 50% of the species found in original propagule banks actually establish. We hypothesize that the expression of this legacy propagule bank is limited by a lack of diversity of microsites and appropriate growing conditions. In an operational‐scale field experiment we manipulated topographical characteristics and substrate materials and explored early vegetation establishment on an east‐ and south‐facing slope. Three different site treatments with different microtopographic characteristics: (1) leveled surface, (2) parallel ridges, and (3) large loose piles were created using salvaged upland and lowland forest floor soil materials. Placing materials in loose hills and providing heterogeneity in substrates more than doubled plant abundance, species richness, and increased the proportion of species that require higher soil moisture. Lower micro‐elevations and northern microaspects of the microtopographic treatments had up to three times higher soil water content and double the species richness. However, the overall slope aspect had a modulating effect on microtopographic positions. The greatest treatment effect of micro‐elevation and microaspect on species richness and plant abundance occurred on the east‐facing slope, while the greatest effect of treatment on the proportion of species requiring higher soil moisture conditions was observed on the south‐facing slope. Variability in microtopography and substrate can create favorable growing conditions at an operational scale and help express a wider range of species from the legacy propagule bank.

Sphagnum moss was collected from ombrotrophic (rain-fed) peat bogs to quantify dust emissions from the open-pit mining and upgrading of Athabasca bituminous sands (ABS). A total of 30 bogs were sampled in the ABS region, and 5 were sampled in central Alberta. Ash was separated into the acid-insoluble ash (AIA) and acid-soluble ash (ASA) fractions using HCl. The AIA concentrations increase toward industry from 0.4 ± 0.5% to 4.7 ± 2.0% over a distance of 30 km; the control site at the Utikuma Region Study Area (URSA) yielded 0.29 ± 0.07% (n = 30). Mass accumulations rates showed similar spatial variation. The morphology and mineralogy of the AIA particles were studied using scanning electron microscopy and energy-dispersive X-ray analysis and the particle size distributions using optical methods. Particle size was more variable in moss closer to industry. Major ions in the ASA fraction showed elevated accumulation rates of Ca, K, Fe, Mg, P, and S, with P being up to 5 times greater in samples nearest industry compared to those in distal locations. Given that P has been regarded as the growth-limiting nutrient in bogs, fertilization of nutrient-poor ecosystems, such as these from fugitive emissions of dusts from open-pit mining, may have long-term ecological ramifications.

We compared median runoff (R) and precipitation (P) relationships over 25 years from 20 mesoscale (50 to 5,000 km2) catchments on the Boreal Plains, Alberta, Canada, to understand controls on water sink and source dynamics in water-limited, low-relief northern environments. Long-term catchment R and runoff efficiency (RP−1) were low and varied spatially by over an order of magnitude (3 to 119 mm/year, 1 to 27%). Intercatchment differences were not associated with small variations in climate. The partitioning of P into evapotranspiration (ET) and R instead reflected the interplay between underlying glacial deposit texture, overlying soil-vegetation land cover, and regional slope. Correlation and principal component analyses results show that peatland-swamp wetlands were the major source areas of water. The lowest estimates of median annual catchment ET (321 to 395 mm) and greatest R (60 to 119 mm, 13 to 27% of P) were observed in low-relief, peatland-swamp dominated catchments, within both fine-textured clay-plain and coarse-textured glacial deposits. In contrast, open-water wetlands and deciduous-mixedwood forest land covers acted as water sinks, and less catchment R was observed with increases in proportional coverage of these land covers. In catchments dominated by hummocky moraines, long-term runoff was restricted to 10 mm/year, or 2% of P. This reflects the poor surface-drainage networks and slightly greater regional slope of the fine-textured glacial deposit, coupled with the large soil-water and depression storage and higher actual ET of associated shallow open-water marsh wetland and deciduous-forest land covers. This intercatchment study enhances current conceptual frameworks for predicting water yield in the Boreal Plains based on the sink and source functions of glacial landforms and soil-vegetation land covers. It offers the capability within this hydro-geoclimatic region to design reclaimed catchments with desired hydrological functionality and associated tolerances to climate or land-use changes and inform land management decisions based on effective catchment-scale conceptual understanding.

In the Boreal Plain of Canada, the margins of peatland ecosystems that regulate solute and nutrient fluxes between peatlands and adjacent mineral uplands are prone to deep peat burning. Whether post-fire carbon accumulation is able to offset large carbon losses associated with the deep burning at peatland margins is unknown. For this reason, we examined how post-fire hydrological conditions (i.e. water table depth and periodicity, soil tension, and surface moisture content) and depth of burn were associated with moss recolonization at the peatland margins of three sites. We then interpreted these findings using a hydrogeological systems approach, given the importance of groundwater in determining conditions in the soil-plant-atmosphere continuum in peatlands. Peatland margins dominated by local groundwater flow from adjacent peatland middles were characterized by dynamic hydrological conditions that, when coupled with lowered peatland margin surface elevations due to deep burning, produced two common hydrological states: 1) flooding during wet periods and 2) rapid water table declines during dry periods. These dynamic hydrological states were unfavorable to peatland moss recolonization and bryophytes typical of post-fire recovery in mineral uplands became established. In contrast, at a peatland margin where post-fire hydrological conditions were moderated by larger-scale groundwater flow, flooding and rapid water table declines were infrequent and, subsequently, greater peatland-dwelling moss recolonization was observed. We argue that peatland margins poorly connected to larger-scale groundwater flow are not only prone to deep burning but also lags in post-fire moss recovery. Consequently, an associated reduction in post-fire peat accumulation may occur and negatively affect the net carbon sink status and ecohydrological and biogeochemical function of these peatlands.

Ecosystems within the subhumid Boreal Plains of Northern Alberta host ecologically and commercially significant habitat and natural resources. However, these ecosystems exist under a delicate hydrologic balance that may be upset as the climate warms by 2 to 5 °C over the next century. In this study, numerical simulations were used to predict climate change impacts at a catchment composed of a mosaic of Boreal Plains ecosystems including a small pond, peatlands with sparse black spruce, and hillslopes with predominantly aspen forests. Simulations were conducted with a fully integrated groundwater–surface water code using a 2-D model previously calibrated to a decade of hydrologic data that included a range in climatic conditions. Projections from 13 climate change scenarios were simulated from 2011 to 2090 and compared to a base case scenario that assumed no climate change. Results indicate peatland water levels may decline by up to 1 m; however, sensitivity simulations indicate that the decline in water levels may be moderated by several feedback mechanisms that restrict evaporative losses and moderate water level changes. In contrast, higher evapotranspiration losses from the aspen hillslopes are predicted to result in near-surface soils becoming increasingly drier. Thus, the aspen may frequently be water stressed and increasingly susceptible to secondary maladies such as pests and disease. Reduced pond water levels are also predicted with the development of frequent ephemeral conditions in warmer and drier scenarios. Concurrent decreases in stream flow may further impact downstream ecosystems. Further research into the regional health and sustainability of Boreal Plains ecosystems is warranted and could benefit from the development of improved numerical tools capable of extending the processes considered.

Over the last several decades the hydrologically sensitive Boreal Plains ecoregion of Western Canada has experienced significant warming and drying. To better predict implications of land cover changes on evapotranspiration (ET) and future water resources in this region, high resolution light detection and ranging and energy balance data are used here to spatially parameterize the Penman-Monteith ET model. Within a 5 km × 5 km area of peatland ecosystems, riparian boundaries, and upland mixedwood forests, the influence of land cover heterogeneity on the accuracy of modeled ET is examined at pixel sizes of 1, 10, 25, 250, 500, and 1,000 m, representing resolutions common to popular satellite products (SPOT, Landsat, and MODIS). Modeled ET was compared with tower-based eddy covariance measurements using a weighted flux footprint model. Errors range from 10% to 36% of measured fluxes and results indicate that sensors with small pixel sizes (1 m) offer significantly better accuracy in large heterogeneous flux footprints, while a wider range of pixel sizes ( 500 m) pixel sizes offered significantly less accuracy, although changes in pixel size within this range offered comparable results. (Less)

The objective of this study was to develop a decision-based methodology, focused on data fusion for wetland classification based on surface water hydroperiod and associated riparian (transitional area between aquatic and upland zones) vegetation community attributes. Multi-temporal, multi-mode data were examined from airborne Lidar (Teledyne Optech, Inc., Toronto, ON, Canada, Titan), synthetic aperture radar (Radarsat-2, single and quad polarization), and optical (SPOT) sensors with near-coincident acquisition dates. Results were compared with 31 field measurement points for six wetlands at riparian transition zones and surface water extents in the Utikuma Regional Study Area (URSA). The methodology was repeated in the Peace-Athabasca Delta (PAD) to determine the transferability of the methods to other boreal environments. Water mask frequency analysis showed accuracies of 93% to 97%, and kappa values of 0.8–0.9 when compared to optical data. Concordance results comparing the semi-permanent/permanent hydroperiod between 2015 and 2016 were found to be 98% similar, suggesting little change in wetland surface water extent between these two years. The results illustrate that the decision-based methodology and data fusion could be applied to a wide range of boreal wetland types and, so far, is not geographically limited. This provides a platform for land use permitting, reclamation monitoring, and wetland regulation in a region of rapid development and uncertainty due to climate change. The methodology offers an innovative time series-based boreal wetland classification approach using data fusion of multiple remote sensing data sources.

Temperatures at the soil–atmosphere interface influence ecosystem function by driving nonlinear terrestrial biogeochemical, ecohydrological, and micrometeorological processes. Whilst climate, soil and vegetation controls on spatially average ecosystem temperatures are recognised, how interacting and heterogeneous ecosystem layers create spatio-temporal complex thermal ecosystems has not been determined. Such thermal hot spots and hot moments may underpin the capability of ecosystems to support biological and biogeochemical diversity and control the likelihood of tipping points in system-regulating feedbacks being locally exceeded. This is of notable importance in peatlands, where soil temperatures control the storage of their associated globally important carbon stocks. Here, through the application of high spatio-temporal resolution surface temperature data and peat thermal modelling, we assess the impact of system heterogeneity (spatio-temporal impact of the following system layers: tree, shrubs, microtopography, groundcover species and sub-surface ice) on surface temperature regimes. We show (a) that peat-surface thermal hotspot intensity and longevity is linked to system heterogeneity and (b) that not all system layers have an equal influence over the peat-surface thermal regime and extreme temperatures; thermal heterogeneity increases up to a maximum of five layers of heterogeneity and decreases thereafter. The results crucially demonstrate that such changes in the spatio-temporal thermal dynamics and extremes may occur without significant changes in median temperatures. This is important to the conceptual understanding of peatland responses and ecosystem resilience to disturbance. It emphasises the need to determine the potential for transitions in magnitude, longevity and locality of small-scale thermal extremes to induce functional transitions that propagate through given ecosystems, and to characterise the impact of such small-scale spatio-temporal complexity on ecosystem scale biogeochemical and ecohydrological function.

Peatland development occurs naturally over long periods of time in response to climate, geology, hydrology and vegetation. Open-pit oil sands mining activities in Northern Alberta result in large-scale removal of the surficial landscape, which comprises many (~ 50%) peatlands, approximately 90% of which are fens with a wide range of peat thicknesses ( Future landscape design plans could benefit from a change of perception of the role of peatlands in the landscape. This change should involve a shift away from viewing wetlands as landforms constrained to low-lying areas within the reclaimed landscape, and towards recognizing that peatlands can function as both a sink and source of water to the remainder of the catchment. Wetland interconnectivity within the reconstructed landscape could increase water detention and storage during wet periods, which would benefit both the wetlands and the forestlands during dry periods. The assessment of the success of these constructed systems should be a reflection of our ability to correctly and accurately predict the influence of external forcings (e.g., climate) on the processes operating within a newly constructed system. Short timeframes (~ 5 years) are sufficient to characterize a range of processes operating in the constructed ecosystems; however, longer time periods will reduce uncertainty in the assessment of the system's successional pathway. The design of future constructed fen peatlands must employ an adaptive approach that assimilates the knowledge developed in the current research and the information attained over the longer-term to guide the design of future fen systems.

Summary A comparative study of three shallow lake catchments in contrasting glacial landscapes (coarse-textured outwash, fine-textured-till hummocky moraines and glacio-lacustrine clay-till plains) demonstrated a distinct landform control on the proportion and type of surface and groundwater sources influencing total phosphorus ([P]) and total dissolved phosphorus ([DP]) concentrations, and P budgets of lakes on the Boreal Plain of the Western Boreal Forest, Alberta, Canada. Lakes located on fine-textured landforms had high [P] and [DP] (median 148 and 148 μg L −1 glacio-lacustrine plains; 99 and 63 μg L −1 moraine, respectively) linked to shallow groundwater loadings from near-surface peat with high [P] from adjacent wetlands. In contrast, the lowest lake [P] and [DP] (median 50 and 11 μg L −1 , respectively) occurred on the coarse-textured landform, reflecting greater inputs of deep mineral-groundwater with low [P] from quartz-rich substrates. Annual lake P budgets reflected lake connectivity to the surrounding landform and relative contributions of P by surface versus groundwater. They also reflected distinct scales of groundwater (larger-scale versus short, shallow-flow paths) with differing [P] between landform types and occurrence of internal biogeochemical P cycling within landforms. A regional lake survey reflected trends from the catchment-scale, linking landform type to potential P sources as well as topographic position to potential trophic status across the Boreal Plain. Together, the results provide a conceptual framework for the scale of interactions between lakes and surrounding source waters influencing P loadings in differing hydrogeological landscapes, important to management strategies and predicting impacts of land-use disturbances on productivity of Boreal Plain lakes.

The Al-Pac Catchment Experiment (ACE) was initiated in 2005 to examine the influence of aspen harvest and linear disturbances on water and energy movement in Boreal Plain (BP) ecosystems. A paired, pre- and post- harvest experiment in aspen-dominated stands was conducted on two meso-scale (10–20 km2) stream catchments with a range of surficial geology and low relief. Comparing flow two years pre-harvest and three years post-harvest indicated no observable differences in low and high flow discharge or geochemistry concentrations between reference and harvested catchment outflows. Reduced evapotranspiration in harvested relative to references catchments was short lived. Soil and groundwater storage buffered the impacts of harvesting on catchment stream flow and large time lags of up to four years were observed in initial response. Due to the low relief, deep and variable surficial geology and storage potential interacting with seasonal and decadal wet and dry patterns, measures of changes in (and indices of) soil moisture or groundwater recharge and storage are more meaningful than stream flow in assessing hydrologic recovery following harvesting. This study has been incorporated into hydrogeological framework to develop effective planning tools that can be used to maximize harvesting and hauling efficiencies.

The Hydrology Ecology And Disturbance (HEAD-1 and HEAD-2) research programs in the Western Boreal Plains of North-Central Alberta, has provided objective delineation and determination of landscape units characterized by geology and climate. From these landscape indices can be developed that provide information on the scale at which forest, wetland, and aquatic systems are linked to their surroundings and the potential response of an area to particular disturbances. In collaboration with industry, government and NGO planners and ecologists this work establishes a hydrologic risk planning process that evaluates the ecological risk and monetary costs of forest harvest on forest succession and water quality and quantity.

There is an urgent need to include northern peatland hydrology in global Earth system models to better understand land-atmosphere interactions and sensitivities of peatland functions to climate change, and, ultimately, to improve climate change predictions. In this study, we introduced for the first time peatland-specific model physics into an assimilation scheme for L-band brightness temperature (Tb) data from the Soil Moisture Ocean Salinity (SMOS) mission to improve groundwater table estimates. We conducted two sets of model-only and data assimilation experiments using the Catchment Land Surface Model (CLSM), applying (over peatlands only) in one of them a peatland-specific adaptation (PEATCLSM). The evaluation against in-situ measurements of peatland groundwater table depth indicates the superiority of PEATCLSM model physics and additionally improved performance after assimilating SMOS Tb observations. The better performance of PEATCLSM over nearly all Northern Hemisphere peatlands is further supported by the better agreement between SMOS Tb observations and Tb estimates from the model-only and data assimilation runs. Within the data assimilation scheme, PEATCLSM reduces Tb observation-minus-forecast residuals and leads to reduced data assimilation updates of water storage components and, thus, reduced water budget imbalances in the assimilation system. ispartof: Remote Sensing Of Environment vol:246 status: Published online

It is common to conceptualize the water table as a subdued replica of surface topography, where groundwater recharges at, and flows from, topographic highs and flows to, and discharges at, topographic lows, in humid (i.e. wetter) environments. This concept is also regularly applied to peatland hydrology, where hydraulic gradients are shown to be towards the peatland. However, this may not be a realistic representation of hydrology for low-relief and sub-humid regions. While it is widely accepted that peatlands maintain internal water tables in drought conditions through a system of autogenic negative feedback loops, there is a general lack of knowledge concerning the controls on, and patterns of, forestland hydrologic process that drive the hydraulic gradients between wetlands and their adjacent forestlands in water-limited conditions in low-relief areas. This study identifies the hydrologic function (i.e. source or sink of water) of forested uplands and peatlands in the Boreal Plains region of Canada and demonstrates that during a mesic (non-drought) year most peatlands are, in fact, potential sources of groundwater to adjacent forestlands. Sixteen forestland-peatland pairs were selected to represent a spectrum of forested hummock and peatland morphometries, topographic positions, and geologic settings. Hydraulic gradients determined for each well pair during the ice-off season demonstrate that the dominant gradient under mesic climatic conditions is from peatlands to adjacent forestlands, opposite of the topographic gradient, and that the sink-source function of each land unit does not change seasonally. Water table depressions under each forested hummock indicate that boreal forestlands are not reliable sources of groundwater recharge, spatially or temporally, which supports previous research showing that peatlands are the primary water source for runoff; illustrating the need for alternative conceptualizations of catchment hydrology in water limited regions of the boreal. Social Media Summary. Forests are poor sources of water to boreal peatlands and landscapes due to water table depressions.

Peatlands play a vital role in the global carbon cycle, acting as one of the most important global carbon sinks. However, an understanding of their environmental processes, particularly in relation to a changing climate, remains inchoate. In particular, the role seasonal ice or frost layers play in altering spring water balance, and thus vulnerability to deep smoldering combustion during wildfire is not fully understood. Continental boreal peatlands are characterized by periodic wildfire disturbance, which releases carbon, but can also inhibit short-term peat productivity and carbon sequestration as the peatland recovers, with recovery timescales linked to the severity or depth of burning. The presence of seasonal frost layers coincides with drier spring conditions and an enhanced risk of wildfire. Two-dimensional numerical modelling was conducted using HYDRUS-2D, a variably saturated flow model, to simulate water balance in the vadose zone and assess vulnerability to fire during prolonged rain free periods in the presence of continuous and discontinuous frost. Our results show there is a lack of horizontal water transfer which increases spatial variability in water balance and leads to pronounced heterogeneity in the risk of smoldering combustion and the potential for deep combustion at hummock-hollow interfaces. Peatlands are broadly divided into areas which are characterized by a dry near-surface and high water contents at depth (water conserving), and those with a wetter near-surface, but comparatively lower water contents at depth (productive). Those areas with dry near-surfaces will be more vulnerable to wildfire and characterize around 50 % of hummocks and 25 % of hollows. In the presence of a seasonal frost layer productive peat layers in hollows will show substantial drying out due to the frost layer disconnecting the surface from the water table; this approximately doubles the proportion of hollows vulnerable to wildfire. Breaks in the frost layer allows areas to maintain hydrological connectivity to a falling water table, but this connectivity is limited in lateral extent and can drive further spatial heterogeneity in vulnerability to wildfire ignition in the weeks when the frost layer begins to thaw.

Peatland ecosystems are globally important carbon and terrestrial surface water stores that have formed over millennia. These ecosystems have likely optimized their ecohydrological function over the long-term development of their soil hydraulic properties. The optimization of peat hydraulic properties is examined to determine which of the following conditions peatland ecosystems target during this development: (i) maximize carbon accumulation, (ii) maximize water storage, or (iii) balance carbon profit across hydrological disturbances. To identify this control, the short-term hydrological response of a 0.5-m-deep peat profile was simulated during a 50-day rain-free period. A total of 5000 Monte-Carlo model realizations were conducted, with peat hydraulic properties differing between each realization (values derived from known probability distributions). Saturated hydraulic conductivity (Ks) and empirical van Genuchten water retention parameter α were shown to provide a first order control on simulated water tensions. For hypothetical combinations of Ks and α, the probability that water tension exceeds the ecologically important threshold of 100 mb within 24 h showed a bimodal distribution. A peak at high probabilities was associated with profiles of high Ks and low α. Such a profile is optimized for water storage. A peak at low probabilities is associated with low Ks, high α, and is optimized for carbon accumulation. Actual hydraulic properties from five northern peatlands fall between this binominal distribution, balancing the competing demands of carbon accumulation and water storage. We argue that peat hydraulic properties are thus optimized to maximize water use efficiency and that this optimization occurs over a centennial to millennial timescale. Copyright © 2015 John Wiley & Sons, Ltd.

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. Copyright © 2015 John Wiley & Sons, Ltd.

Summary Wildfire is the largest disturbance affecting boreal peatlands, however, little is known about the controls on post-fire peatland vegetation recovery. While small-scale variation in burn severity can reduce post-fire moss water availability, high water table (WT) positions following wildfire are also critical to enable the re-establishment of keystone peatland mosses ( i.e. Sphagnum ). Thus, post-fire moss water availability is also likely a function of landscape-scale controls on peatland WT dynamics, specifically, connectivity to groundwater flow systems ( i.e. hydrogeological setting). For this reason, we assessed the interacting controls of hydrogeological setting and burn severity on post-fire moss water availability in three burned, Sphagnum -dominated peatlands in Alberta’s Boreal Plains. At all sites, variation in burn severity resulted in a dichotomy between post-fire surface covers that: (1) exhibited low water availability, regardless of WT position, and had minimal ( i.e. lightly burned feather mosses and severely burned Sphagnum fuscum ) or (2) exhibited high water availability, depending on WT position, and had substantial (>50%) moss re-establishment ( i.e. lightly burned S. fuscum and where depth of burn was >0.05 m). Notably, hydrogeological setting influenced the spatial coverage of these post-fire surface covers by influencing pre-fire WTs and stand characteristics ( e.g. , shading). Because feather moss cover is controlled by tree shading, lightly burned feather mosses were ubiquitous (>25%) in drier peatlands (deeper pre-fire WTs) that were densely treed and had little connection to large groundwater flow systems. Moreover, hydrogeological setting also controlled post-fire WT positions, thereby affecting moss re-establishment in post-fire surface covers that were dependent on WT position ( e.g. , lightly burned S. fuscum ). Accordingly, higher recolonization rates were observed in a peatland located in a groundwater flow through system that had a shallow post-fire WT. Therefore, we argue that hydrogeological setting influences post-fire recovery in two ways: (1) by influencing vegetation structure prior to wildfire, thereby controlling the coverage of post-fire surface covers and (2) by influencing post-fire WT positions. These results suggest that post-fire moss recovery in peatlands isolated from groundwater flow systems may be particularly susceptible to droughts and future climate change.