James Bay Lowlands Research Articles

Toward a common categorization for valued components: using a review of valued components and indicators in the lower James Bay Region of Ontario and Quebec, Canada, to support cumulative impact science in Canada

ABSTRACT Cumulative impacts and regional assessments (RA) require the integration and analysis of large quantities of interdisciplinary scientific information. Yet, the information available is not often readily accessible nor standardized across impact assessments. We proposed here a categorization of valued components that have been derived from projects in the James Bay Lowlands and that is aligned with the IAAC’s Tailored Impact Statement Guidelines (TISG) template, a key document to support project and regional impact assessment deliverables. We compiled valued components and indicators from previous and ongoing environmental impact assessments in the James Bay Lowlands. We identified trends associated with valued components and indicators and combined these trends with the TISG. We then derived a categorization of valued components nested under seven systems. From the reviewed work, we identified 197 valued components (23% valued components were common for two or more projects) and 313 indicators. Our categorization is composed of seven systems and 34 potential valued components allowing for easy connections between future project-level impact assessments and RAs. Our categorization is a valuable communication tool across all stakeholders and rightsholders involved in impact assessments, including communities, Indigenous leaders, IA practitioners, industry, and government.

Soil Nutrient Supply in Cultivated Bush Bean–Potato Intercropping Grown in Subarctic Soil Managed with Agroforestry

To address food insecurity in northern Canada, some isolated communities started gardening initiatives to reduce dependencies on expensive foods flown in to communities. From 2012–2014, soils in northern Ontario James Bay lowlands were cultivated with bush beans and potatoes, grown in sole and intercropping configurations, in an open field and an agroforestry system enclosed by willow trees. The objective of this study was to compare the supply rates of 15 plant-available nutrients in these soils using in situ ion exchange membranes. After three years of cultivation, the agroforestry site had significantly greater supply of PO4, Ca, and Zn and these nutrients had positive correlations with yield. By contrast, the open site had significantly greater supply of Mg, SO4, and B; these nutrients, and Al, had negative correlations with yield. Whilst there were no differences between sole and intercropping configurations, significantly greater supply of NO3, Ca, Cu, Fe, and Zn occurred early in the growing season, compared to significantly greater supply of K, SO4, B, and Al later in the season. Significantly greater yields have been harvested in the agroforestry site and it is suspected that the presence of a willow shelterbelt improves the microclimate and plant-available PO4, Ca, and Zn.

Project George: An Indigenous Land-Based Approach to Resilience for Youth


 
 
 The research shared in this article seeks an understanding of Indigenous resilience within the context of a culturally responsive land-based initiative, Project George, led by the Moose Cree First Nation, also known as the Omushkego people. The initiative centres core Cree values, community engagement, and land-based skills to ensure the well-being of youth. Their Homeland is located in the waterways and on the western shores of the Hudson and James Bay Lowlands in Ontario, Canada. The methodology involved researcher participation and engagement as part of a 4-month field presence; informal conversations and visiting; as well as formal semistructured interviews with community members over 4 years from 2012 to 2015. The research explores the benefits and challenges of a land-based program by highlighting the experiences and voices of community and program participants who directly engaged with Project George. The findings show that land-based learning initiatives inspired and driven by Indigenous people foster a regenerative approach to wellness based on relation to land, culture, and identity. A return to land-based learning responds to the ongoing colonial complexities affecting the health and wellness of Indigenous youth in Canada and draws strength from the people’s resilient practices.
 
 

Sinkholes and their impacts on karst hydrogeology in a peatland complex of Northern Ontario, Canada

Pliocene glaciations, post-glacial Tyrrell Sea deposition, peatland formation, and continuous isostatic uplift have created a unique environment for karst development on the Paleozoic carbonate rocks within the James Bay Lowland of Canada. Four types of sinkhole and two karst hydrogeological systems have been recognized in the study area. The hydrogeologically active karst system consists of solution sinkholes, solutionally enlarged fractures, and collapse sinkholes that have developed after the area emerged from the Tyrrell Sea approximately 4400 years ago. The active karst system encompasses the exposed reefal limestone of the Silurian Attawapiskat Formation along the Attawapiskat River and Nayshkootayaow River and isolated bioherms that protrude above the surrounding flat but poorly drained peatland between the two major rivers. The second karst system is in the form of paleokarst formed in the underlying limestone but buried beneath the peat and marine sediments. Although these buried sinkholes were only visible at excavation sites where these features were exposed, it is likely that they underlie most of the study area. Another form of paleokarst is the Bedrock Trench that cut through most of the Paleozoic formation to a depth of approximately 200 m. The bedrock trench encompassed an area of more than 3 km2, was filled with unconsolidated materials, and did not have strong hydraulic connections to the active karst system. Formation mechanism of this bedrock trench is inconclusive but may result from polygenetic processes including glacial scouring and bedrock dissolution. Recognition of these two karst systems helps understand potential hydrogeological changes in response to continuous isostatic uplift and dewatering activities in this region.

Microtopographical and hydrophysical controls on subsurface flow and solute transport: A continuous solute release experiment in a subarctic bog

AbstractResource extraction and transportation activities in subarctic Canada can result in the unintentional release of contaminants into the surrounding peatlands. In the event of a release, a thorough understanding of solute transport within the saturated zone is necessary to predict plume fate and the potential impacts on peatland ecosystems. To better characterize contaminant transport in these systems, approximately 13,000 L/day of sodium chloride tracer (200 mg/L) was released into a bog in the James Bay Lowland. The tracer was pumped into a fully penetrating well (1.5 m) between July 5 and August 18, 2015. Horizontal and vertical plume development was measured via in situ specific conductance and water table depth from an adaptive monitoring network. Over the spill period, the bulk of the plume travelled a lateral distance of 100 m in the direction of the slight regional groundwater and topographical slope. The plume shape was irregular and followed the hollows, indicating preferential flow paths due to the site microtopography. Saturated transport of the tracer occurred primarily at ~25 cm below ground surface (bgs), and at a discontinuous high hydraulic conductivity layer ~125 cm bgs due to a complex and heterogeneous vertical hydraulic conductivity profile. Plume measurement was confounded by a large amount of precipitation (233 mm over the study period) that temporarily diluted the tracer in the highly conductive upper peat layer. Longitudinal solute advection can be approximated using local water table information (i.e., depth and gradient); microtopography; and meteorological conditions. Vertical distribution of solute within the peat profile is far more complex due to the heterogeneous subsurface; characterization would be aided by a detailed understanding of the site‐specific peat profile; the degree of decomposition; and the type of contaminant (e.g., reactive/nonreactive). The results of this research highlight the difficulty of tracking a contaminant spill in bogs and provide a benchmark for the characterization of the short‐term fate of a plume in these complex systems.

Evaluating the potential of testate amoebae as indicators of hydrological conditions in boreal forested peatlands

Testate amoebae are common proxies of past hydrological conditions in peatlands and are increasingly used as indicators of ecosystems ecological integrity. The ecology of these microorganisms is relatively well documented in non-forested ombrotrophic peatlands but there is a lack of data from forested peatlands, which are important ecosystems in boreal regions. This study provides the first testate amoebae modern training set (n = 72) from forested peatlands of the James Bay lowlands, eastern Canada. The relationships between testate amoeba communities and environmental variables (pH, water table depth, canopy openness, mineral particles concentration) were investigated using canonical correspondence analyses. Our data have shown that testate amoebae are sensitive environmental indicators in forested peatlands and can be used to reconstruct past hydrological conditions for these environments. A transfer function for water table depth (WTD) reconstructions was developed using weighted averaging models and was tested on a fossil testate amoebae record. In comparing forested and non-forested peatlands datasets we have shown that testate amoebae occupy similar ecological niches with respect to surface wetness in both ecosystems, but that their WTD optima is much higher (drier) in forested peatlands. The results show that the diversity and composition of testate amoeba assemblages do not vary significantly at the microform scale. This study provides new knowledge on testate amoebae ecology in forested peatlands that will improve further transfer function development in peatland ecosystems. This will allow a better evaluation of the responses of boreal forested peatlands to climate change, ecological disturbances and human activities.

Analysis of Tyrrell Sea Deposits from the Vicinity of the Victor Diamond Mine: Comparison of Three North American Clay Deposits

he De Beers Victor Mine is an open pit diamond mine, and is located in the James Bay lowlands. The lowlands are characterized by extensive peatlands overlying Tyrell Sea sediments. One of the potential impacts of open pit mining, and the focus of the current work, is the potential for differential subsistence in the Tyrell Sea sediments owing to continuous groundwater withdrawal from the underlying limestone aquifers. To fully understand the potential effects of subsistence, a better understanding of the nature and properties of the Tyrell Sea sediments is needed. This will be achieved by analyzing various properties of samples collected from the Victor Diamond Mine, and comparing those properties with values from Lake Agassiz sediments and Bearpaw Shale. Properties such as hydraulic conductivity, grain size, plastic and liquid limit, and mineralogy will be compared. It is expected that the samples from the Victor Mine are a rock flour dominated by clay fraction, composed mostly of finely ground carbonates. The sediments are expected to have high plasticity, low hydraulic conductivity, and moisture content too low for that of true clay.

Water budget, performance of evapotranspiration formulations, and their impact on hydrological modeling of a small boreal peatland-dominated watershed

Peatlands occupy around 13% of the land cover of Canada, and thus they play a key role in the water balance at high latitudes. They are well known for having substantial water loss due to evapotranspiration. Since measurements of evapotranspiration are scarce over these environments, hydrologists generally rely on models of varying complexity to evaluate these water exchanges in the global watershed balance. This study quantifies the water budget of a small boreal peatland-dominated watershed. We assess the performance of three evapotranspiration models in comparison with in situ observations and the impact of using these models in the hydrological modeling of the watershed. The study site (∼1 km2) is located in the eastern James Bay lowlands, Québec, Canada. During summer 2012, an eddy flux tower measured evapotranspiration continuously, while a trapezoidal flume monitored streamflow at the watershed outlet. We estimated evapotranspiration with a combinational model (Penman), a radiation-based model (Priestley–Taylor), and a temperature-based model (Hydro-Québec), and performed the hydrological modeling of the watershed with HYDROTEL, a physically based semi-distributed model. Our results show that the Penman and Priestley–Taylor models reproduce the observations with the highest precision, while a substantial drop in performance occurs with the Hydro-Québec model. However, these discrepancies did not appear to reduce the hydrological model efficiency, at least from what can be concluded from a 3-month modeling period. HYDROTEL appears sensitive to evapotranspiration inputs, but calibration of model parameters can compensate for the differences. These findings still need to be confirmed with longer modeling periods.

Nutrient Concentrations of Bush Bean (Phaseolus vulgaris L.) and Potato (Solanum tuberosum L.) Cultivated in Subarctic Soils Managed with Intercropping and Willow (Salix spp.) Agroforestry

To ease food insecurities in northern Canada, some remote communities started gardening initiatives to gain more access to locally grown foods. Bush beans (Phaseolus vulgaris L.) and potatoes (Solanum tuberosum L.) were assessed for N, P, K, Mg, and Ca concentrations of foliage as indicators of plant nutrition in a calcareous silty loam soil of northern Ontario James Bay lowlands. Crops were grown in sole cropping and intercropping configurations, with comparisons made between an open field and an agroforestry site enclosed with willow (Salix spp.) trees. Foliage chemical analysis of the sites revealed an abundance of Ca, adequacies for Mg and N, and deficiencies in P and K. Intercropping bean and potato did not show significant crop–crop facilitation for nutrients. The agroforestry site showed to be a superior management practice for the James Bay lowland region, specifically for P. The agroforestry site had significantly greater P for bean plant (p = 0.024) and potato foliage (p = 0.002) compared to the open site. It is suspected that the presence of willows improve plant available P to bean and potatoes by tree root—crop root interactions and microclimate enhancements.

Using Thermal Profiling as an Indicator for Groundwater Discharge

Temperature can be used in order to selectively and intelligently deploy monitoring wells to measure groundwater discharge to surface water. The temperature of Groundwater is constant, reflecting average annual temperature, whereas the temperature of surface water fluctuates daily and seasonally. The contrast can be found by scanning sediment for variations in temperature. In effect, this disparity causes ‘cold spots’ in surface water, such as lakes, which are often felt by swimmers as a brisk interruption to the warmth of the lake. This technique of scanning shorelines for evidence of groundwater discharge to surface water was employed at three locations. These sites are all located in Ontario; one, Victor, is in the James Bay Lowlands, while the remaining two, Frontenac Landfill and the Former Davis Tannery, are in southeastern Ontario, namely Kingston. Victor is a pristine location, while the two in Kingston are both contaminated. Each has limestone bedrock overlain by glacial sediment and wetlands. The two in southern Ontario have marshes, while the site in northern Ontario is a peatland. The climate of the Kingston locations is temperate and continental with influence of the Great Lakes whereas Victor is subarctic and wet. The stratigraphy, or succession of sediments that overly the bedrock, has been heavily disturbed by anthropogenic processes at the two sites in Kingston, making groundwater flow difficult to predict. Determining groundwater discharge will aid other work at each site. At the Former Davis Tannery it is critical to trace contaminants, particularly fugitive emissions that may discharge into adjacent surface water. At Frontenac, the study will help understand the implications of the landfill on the marsh which flanks it. Furthermore, the study of groundwater discharge at Victor can provide information about the hydrogeology of the region, as few studies have taken place in this region until recently. Two different types and probes of various lengths were manually inserted into sediment to identify temperature differences. Location and temperature readings were recorded. The range of temperatures at each site was as follows: Frontenac (10.2°C to 13.4°C), Victor (0.5°C to 20.4°C), and the Former Davis Tannery (8.2°C to 23.1°C). These differences indicate that thermal profiling can be used in order to scan for groundwater discharge. Furthermore, the ease with which this method can be accomplished makes it a viable solution for consulting firms, researchers, or others looking to characterize groundwater/surface water interactions.

Factors Affecting Abundance of Beaver Dams in Forested Landscapes

Beavers are ecosystem engineers that contribute to landscape heterogeneity in North American boreal forests. Despite the importance of beavers on landscapes, beaver distribution is still poorly understood, particularly at large spatial scales and in different ecoregions. The goal of our study was to determine the main environmental features affecting beaver dam abundance across ecoregions. We quantified the spatial distribution of beaver dams in Quebec forests using 257 systematically distributed provincial forestry maps, in which we sampled 1025 plots of 25 km2 in an area several orders of magnitude larger than in previous studies. The study area, covering over 300,000 km2, spanned over six ecoregions (Appalachians, Meridional Laurentians, Central Laurentians, Abitibi and James Bay Lowlands, Mistassini, and Anticosti Island). We constructed 17 candidate regression models using a negative binomial distribution with variables based on different hypotheses to explain beaver dam abundance. The mean stream gradient was the top variable influencing dam abundance, followed by the cover of non-forested land. However, there was substantial variability among ecoregions, as the models that included the random effect of hardwood cover and non-forested cover ranked higher than models without these variables. We conclude that such regional variation in factors affecting dam distribution patterns should be taken into account when establishing beaver management plans.

The transport dynamics of chloride and sodium in a ladder fen during a continuous wastewater polishing experiment

Ladder fen peatlands have excellent potential for wastewater polishing as they naturally contain both open water (pools) and subsurface (peat) treatment landforms; however, there is a poor understanding of solute transport in ladder fens with and without the increased hydrological load imposed by wastewater discharge. To better understand solute transport in ladder fens under wastewater polishing conditions a continuous solute (NaCl) tracer experiment (38m3day−1 of water, chloride – 47.2mgL−1, and sodium – 25.3mgL−1) was conducted during the summer of 2014 (day of year 192–243) in a small ladder fen in the James Bay Lowland. The transmissivity distribution and effective porosity (average 0.5) of the peat ribs were determined through repeated bail tests and the drainable porosity of 18 peat cores at −100mb, respectively. Water samples were taken at least every 7days to capture the solute (sodium and chloride) plumes. Both solute plumes never reached the site outflow (∼250m downgradient) and displayed complex plume morphology, typically following the patterns of higher hydraulic conductivity within the upper 0.1m of the saturated peat, rather than the microtopography. Based on the 50% breakthrough isotherms, sodium and chloride were transported at an average solute velocity of 1.9 and 1.1mday−1, respectively (average linear groundwater velocity=2.1mday−1); thus, the solutes were retarded by a factor of 2.1 and 1.2 for sodium and chloride, respectively. Due to the inherent retardation of solutes into inactive pores and relatively high solute residence times, this study demonstrates the potential for wastewater polishing in ladder fens.

Experimental hydrological forcing to illustrate water flow processes of a subarctic ladder fen peatland

AbstractLarge peatland complexes dominate the landscape of the James Bay Lowland in subarctic Ontario, Canada. However, there is not a thorough understanding of the hydrological processes occurring in these important systems, particularly how ladder fens connect large domed bogs to the aquatic ecosystems that drain the peatland complex. Ladder fens consist of a pool‐rib topography where flow downgradient is controlled by the peat ribs. Within the ribs, low‐lying preferential flow paths typically enhance the transmission of water, whereas the elevated ridge microforms impede water flow to downgradient aquatic ecosystems. To assess the hydrological connectivity, we study the role of the water table, peat transmissivity, and microtopography of a small ladder fen for 3 summers (2013–2015) in the James Bay Lowland. The system was manipulated with a sustained hydrological forcing (water addition) to the upslope boundary of the fen during 2014 (38 m3/day) and 2015 (30 m3/day). There was an exponential increase in transmissivity towards the peat surface due to extremely high‐hydraulic conductivities within the upper few centimeters of the peat deposit. At the maximum water table, the saturated hydraulic conductivity of the 0.1 m layer of peat below the water table varied depending on peat microtopography (preferential flow paths = 42–598 m/day and ridges = 16–52 m/day), resulting in high‐hydrological connectivity periods. Furthermore, during 2015, there was an abnormally large amount of precipitation (300 mm vs. long‐term average ~ 100 mm) that resulted in complete surface water connectivity of the site. This caused rapid movement of water from the head of system to the outlet (~15 hr) and runoff ratios >1, compared to low‐water table periods (runoff ratio ~ 0.05). This study highlights the profound importance of the transmissivity–water table feedback mechanism in ladder fens, on controlling the water retention and drainage of large peatland complexes.

Increased atmospheric dust deposition during the Neoglacial in a boreal peat bog from north-eastern Canada

Dust deposition in north-eastern Canada was estimated from the geochemical signature of a boreal peat bog from the James Bay lowlands. The rare earth elements and other lithogenic elements, as well as Nd isotopes were measured by Q-ICP-MS, ICP-OES and MC-ICP-MS, respectively along a 4.20m peat core covering the last 7000years. A principal component analysis performed on the geochemical dataset shows that REEs display the same chemical behavior as other lithogenic elements such as Al and Ti, which suggests that they are immobile in the peat column and can be used as tracers of dust deposition. After 4000calyrBP, peaks in dust deposition associated with greater variability in testate amoebae assemblages and plant macrofossil composition as well as a change in ɛNd values are observed. Between 7000 and 4100calyrBP, the ɛNd values varied from −36 to −29, while they gradually increased from 4100calyrBP until 1500calyrBP, suggesting proportionally less dust from local source(s) is deposited in favor of more regional source(s). From 1500calyrBP, ɛNd values remained relatively stable around −15 and −12. Most of the dust peaks correspond to documented cold and dry periods likely linked to intrusion of arctic air masses. A migration of the polar front might explain the more frequent intrusion of Arctic air masses in the region and the greater variability in the LG2 record over the last 4000years.

Boreal peatland water table depth and carbon accumulation during the Holocene thermal maximum, Roman Warm Period, and Medieval Climate Anomaly

The Boreal Shield and James Bay Lowland regions of Ontario have few Holocene reconstructions specific to surface moisture despite their potential importance to documenting the geographic patterns and teleconnections of Holocene pluvials and droughts, as well as their role in the global carbon cycle. We reconstructed water table depth using preserved testate amoebae in four stratigraphic peatland cores, supplemented with a literature review to investigate the effects of the Holocene Thermal Maximum (HTM) and Medieval Climate Anomaly (MCA) on surface moisture and long-term apparent carbon accumulation (LARCA) in the regions. A 7320 calendar years before AD 1950 (yrBP) length record registered a wet shift at 4600 yrBP in concert with the HTM and a later post-2550 yrBP shift towards wetter and more stable conditions, possibly related to the Roman Warm Period. During the late-Holocene the three most southern boreal records indicated a lack of droughts during the MCA. Medieval pluvials in boreal Ontario would be consistent with North American precipitation patterns under La Niña conditions. Of the three wet-warm periods identified (HTM, 2550 yrBP, MCA), the 2550 yrBP shift had the most consistent positive influence on LARCA regionally. Although past precipitation was positively correlated with temperature in the region, recent drying may be indicative of a fundamental change in evaporation-precipitation balance.

Hydrological functions of a mine-impacted and natural peatland-dominated watershed, James Bay Lowland

Abstract Study region This study was conducted in Northern Ontario, Canada, in the middle of the Hudson-James Bay. Lowland: one of the world’s largest wetland complexes. Study focus Northern latitudes are expected to be the most impacted by climate change in the next century and adding to this stressor are increased mineral exploration activities, such as the De Beers Victor Mine, a large open-pit diamond mine. Because of the extremely low relief and presence of marine sediments, horizontal runoff and vertical seepages losses are minimal. As a consequence of this aquifer dewatering must occur to keep the open-pit mine dry. What is unknown is how the aquifer dewatering would impact the water balance of a peatland-dominated watershed. This study examines 3 years of aquifer dewatering from 2009 to 2011. New hydrological insights Deep seepage (groundwater recharge) varied with marine sediment thickness and represented a significant loss to the local system. Large downward fluxes were also measured in fen systems that are typically local discharge zones. Evaporation rates were also found to be lower in the bogs and fens and where impacted by lower water tables. When evaluating the water balance, with only 14.5% of the watershed impacted by the mine, the hydrological function of the entire watershed is more driven by seasonal climate variations than mine dewatering.

Temperature, oxygen, and vegetation controls on decomposition in a James Bay peatland

AbstractThe biochemical composition of a peat core from James Bay Lowland, Canada, was used to assess the extent of peat decomposition and diagenetic alteration. Our goal was to identify environmental controls on peat decomposition, particularly its sensitivity to naturally occurring changes in temperature, oxygen exposure time, and vegetation. All three varied substantially during the last 7000 years, providing a natural experiment for evaluating their effects on decomposition. The bottom 50 cm of the core formed during the Holocene Climatic Optimum (~7000–4000 years B.P.), when mean annual air temperature was likely 1–2°C warmer than present. A reconstruction of the water table level using testate amoebae indicated oxygen exposure time was highest in the subsequent upper portion of the core between 150 and 225 cm depth (from ~2560 to 4210 years B.P.) and the plant community shifted from mostly Sphagnum to vascular plant dominance. Several independent biochemical indices indicated that decomposition was greatest in this interval. Hydrolysable amino acid yields, hydroxyproline yields, and acid:aldehyde ratios of syringyl lignin phenols were higher, while hydrolysable neutral sugar yields and carbon:nitrogen ratios were lower in this zone of both vascular plant vegetation and elevated oxygen exposure time. Thus, peat formed during the Holocene Climatic Optimum did not appear to be more extensively decomposed than peat formed during subsequent cooler periods. Comparison with a core from the West Siberian Lowland, Russia, indicates that oxygen exposure time and vegetation are both important controls on decomposition, while temperature appears to be of secondary importance. The low apparent sensitivity of decomposition to temperature is consistent with recent observations of a positive correlation between peat accumulation rates and mean annual temperature, suggesting that contemporary warming could enhance peatland carbon sequestration, although this could be offset by an increasing contribution of vascular plants to the vegetation.

Peer review report 1 On “Hydrological functions of a mine-impacted and natural peatland-dominated watershed, James Bay Lowland”

Peer review report 1 On “Hydrological functions of a mine-impacted and natural peatland-dominated watershed, James Bay Lowland”

Analytical solution for enhanced recharge around a bedrock exposure caused by deep-aquifer dewatering through a variable thickness aquitard

In this study an analytical solution was developed to predict steady radially-symmetric percolation rates from an aquifer underlain by a variable thickness aquitard. The solutions consider an aquitard with constant thickness and with radial-symmetrically increasing thickness outward from the center. The solution was used to predict the percolation rate from a peat layer around a bedrock outcrop in the James Bay Lowland near the De Beers Victor diamond mine. In this case the marine sediment layer limited the direct connection between the peat layer and the bedrock as an aquitard. Our zero order solution with constant marine sediment thickness showed the best fit to the steady state water level data of June 2012. It was found that the enhanced recharge around bioherms (i.e., at rates greater than the regional average of 0.7mm/day) will only occur in marine sediments less than 4.3m thick, for extreme depressurization of 30m.

Peatland succession and long-term apparent carbon accumulation in central and northern Ontario, Canada

Despite their importance as globally significant carbon (C) stores, basic knowledge of post-glacial peatland history and C accumulation are lacking for the Canadian Boreal Shield and James Bay Lowland (JBL) of central and northern Ontario, Canada. Radiocarbon dates, plant macrofossil analysis, and soil C estimates from an eight-core transect of the JBL and surrounding regions are used to reconstruct the timings and patterns of fen to bog transitions, and the ranges and patterns of long-term apparent rate of C accumulation (LARCA). Peatland initiation lagged the retreat of the Laurentide ice sheet, the drainage of glacial lakes, and isostatic uplift by 810–6050 years. Transition from Carex-dominated fen to Sphagnum-dominated bog had a median timing of 3500 years following peatland establishment and ranged from 640 to 6970 years. LARCA was variable geographically and over time with median values ranging from 13.4 to 31.6 g C/m2/yr. LARCA anomalies were generally high ~6.1 kyr (kyr = 1000 calibrated years before present (cal. yr BP)) for southern sites, and ~2.5 kyr for the most northern sites, and may be associated with elevated moisture as inferred from a brief review of regional proxy reconstructions. Some sites displayed high LARCA anomalies, changes in plant ecology, or southern site initiation, which may have also been driven by a moist Hypsithermal Period occurring ~4.5 kyr. LARCA increases were not generally associated with high-temperature anomalies during the warm ‘Medieval Climate Anomaly’ compared with the cooler ‘Little Ice Age’; however, there is evidence that the establishment of modern permafrost during the late-Holocene negatively affected C accumulation.