Nigel Roulet

• James McGill Professor of Biogeoscience (PhD)
• McGill University

Restoration of drained and extracted peatlands can potentially return them to carbon dioxide (CO2) sinks, thus acting as significant climate change mitigation. However, whether the restored sites will remain sinks or switch to sources with a changing climate is unknown. Therefore, we adapted the CoupModel to simulate ecosystem CO2 fluxes and the as...

Peat extracted for horticulture is used for growing food, ornamental plants and for soil augmentation. Peatlands are large carbon (C) stores, and the use of extracted peat in aerobic, off-site conditions have implications on the accounting of CO2 emissions. The IPCC (2006, 2013) emission factor for peat use assumes instant oxidation i.e., all extra...

Restoration of drained and extracted peatlands can potentially return them to carbon (C) sinks, thus acting as significant climate change mitigation. However, whether the restored sites will remain C sinks or switch to sources with a changing climate is unknown. Therefore, we adapted the CoupModel to simulate soil atmosphere exchanges and the assoc...

Excess CO2 accumulated in soils is typically transported to the atmosphere through molecular diffusion along a concentration gradient. Because of the slow and constant nature of this process, a steady state between peat CO2 production and emissions is often established. However, in peatland ecosystems, high peat porosity could foster additional non...

Aims Peat is used as a major ingredient of growing media in horticulture. Peat extracted from bogs can be acidic and low in nutrient availability and is therefore mixed with liming agents, nutrients, surfactants, perlite and so on. This study aims to estimate the rates at which raw peat and the modified peat (‘growing media’) decompose to release c...

Peatlands are carbon sinks and have the potential to mitigate global warming. However, it is unclear whether peatlands will remain carbon sinks or switch to carbon sources under global changes, such as climate warming, elevated nitrogen (N) deposition and vegetation composition change. In this study, these global changes were mimicked in a boreal p...

Under the United Nations Framework Convention on Climate Change, Annex 1 countries must report annual carbon dioxide (CO2) emissions from peatlands drained for extraction. However, the Tier 1 emission factor (EF) provided in the IPCC 2014 Wetland Supplement is based mainly on warm season data from a limited number of sites. Here we evaluate the cur...

Northern peatlands are globally significant carbon stores, but the sink strength varies from year to year due to changes in environmental conditions. Ecosystem respiration (ER) is composed of both autotrophic respiration (AR) that consists of respiration by plant parts, and heterotrophic respiration (HR) that consists of respiration by microbial ba...

When extracting peat for horticultural use, drainage ditches are prepared, a peatland’s vegetation is removed, and peat is harvested. These land-use changes dramatically alter the carbon, water, and energy exchanges of the peatland and convert it from a moderate sink to a large source of CO2. We adapted the CoupModel to simulate the soil CO2 emissi...

Draining and extracting peat alters the conditions that control CO2 and CH4 emissions. Carbon (C) emissions from peatlands undergoing horticultural peat extraction are not well constrained due to a lack of measurements. We determine the effect that production duration (years of extraction) has on the CO2 and CH4 emissions from an actively extracted...

The carbon (C) dynamics of northern peatlands are sensitive to hydrological changes owing to ecohydrological feedbacks. We quantified and evaluated the impact of water level variations in a beaver pond (BP) on the CO2 flux dynamics of an adjacent, raised Sphagnum–shrub-dominated bog in southern Canada. We applied the CoupModel to the Mer Bleue bog,...

Ericaceous shrubs adapt to the nutrient‐poor conditions in ombrotrophic peatlands by forming symbiotic associations with ericoid mycorrhizal (ERM) fungi. Increased nutrient availability may diminish the role of ERM pathways in shrub nutrient uptake, consequently altering the biogeochemical cycling within bogs. To explore the significance of ERM fun...

Peatlands are unique and rare ecosystems that, despite covering only around 3-4% of the planet’s land surface, contain up to one-third of the world’s soil carbon, which is twice the amount found in the entire Earth’s forest biomass. Keeping this carbon locked away is absolutely critical for achieving global climate goals. However, about 12% of curr...

Draining and extracting peat alters a peatland’s control of CO2 and CH4 emissions. Carbon (C) emissions from peatlands undergoing extraction are not well constrained due to a lack of measurements. We determine the effect that production duration (years of extraction) has on the CO2 and CH4 emissions from an actively extracted peatland over three ye...

Northern peatlands are globally significant carbon stores, but the sink strength may vary from year-to-year due to variations in environmental and biogeochemical conditions. This variation is mainly brought about by changes in primary production and in autotrophic respiration (AR; respiration by plant parts), components that we understand reasonabl...

Peatlands contain a significant fraction of global soil carbon, but how these reservoirs will respond to the changing climate is still relatively unknown. A global picture of the variations in peat organic matter chemistry will aid our ability to gauge peatland soil response to climate. The goal of this research is to test the hypotheses that (a) p...

Peatland degradation due to human activities is contributing to rising atmospheric CO2 levels. Restoring the carbon (C) sink function in degraded peatlands and preventing further stored C losses is a key climate mitigation strategy, given the global scale of peatland disturbance. Active restoration involving a combination of rewetting and vegetatio...

The carbon (C) dynamics of northern peatlands are sensitive to hydrological changes owing to ecohydrological feedback. We quantified and evaluated the impact of water level variations in a beaver pond (BP) on the CO2 flux dynamics of an adjacent, raised Sphagnum – shrub-dominated bog in southern Canada. We applied the CoupModel to the Mer Bleue bog...

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eas...

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eas...

Northern peatlands have cooled the global climate by accumulating large quantities of soil carbon (C) over thousands of years. Maintaining the C sink function of these peatlands and their immense long‐term soil C stores is critical for achieving net‐zero global carbon dioxide (CO2) emissions by 2050 to mitigate climate warming. One‐quarter of the w...

Northern peatlands are globally significant carbon stores, but the sink strength may vary from year-to-year due to variations in environmental and biogeochemical conditions. This variation is mainly brought about by changes in primary production and ecosystem respiration. The processes that relate to variations in autotrophic respiration (AR; respi...

Peatlands store a large amount of organic carbon and are vulnerable to climate change and human disturbances. However, ecosystem-scale peatland models often do not explicitly simulate the decrease in peat substrate quality, i.e., decomposability or the dynamics of decomposers during peat decomposition, which are key controls in determining peat car...

Current peatland models generally treat vegetation as static, although plant community structure is known to alter as a response to environmental change. Because the vegetation structure and ecosystem functioning are tightly linked, realistic projections of peatland response to climate change require the inclusion of vegetation dynamics in ecosyste...

The aim of this study was to determine the effect of drainage on peat properties, porewater chemistry, and peat decomposition proxies in an ombrogenous peatland in the Hudson Bay Lowland (HBL). We anticipated that drainage would change peatland hydrology, vegetation, and biogeochemistry, leading to an increase in peat decomposition. As indicators o...

Peatlands are important players in climate change–biosphere feedbacks via long-term net carbon (C) accumulation in soil organic matter and as potential net C sources including the potent greenhouse gas methane (CH4). Interactions of climate, site-hydrology, plant community, and groundwater chemical factors influence peatland development and functio...

Peatlands and forests cover large areas of the boreal biome and are critical for global climate regulation. They also regulate regional climate through heat and water vapour exchange with the atmosphere. Understanding how land-atmosphere interactions in peatlands differ from forests may therefore be crucial for modelling boreal climate system dynam...

Climate change has the potential to alter hydrological regimes and to expand saturated areas in permafrost environments, which are important sources of organic carbon. The sources, transfer zones, and delivery mechanisms of carbon into the stream network are controlled by the morphometric properties of the catchment; however, the utility and limita...

Drier conditions caused by drainage for infrastructure development, or associated with global climate warming, may test the resilience of carbon-rich northern peatlands. Feedbacks among biological and hydrological processes maintain the long-term stability of peatlands, but if hydrological thresholds are passed, these feedbacks may be weakened, cau...

Spatial surface patterns of hummocks, hollows, ridges, and pools (microtopography) are common features of many northern peatlands and are particularly distinct within the vast peatlands of the Hudson Bay Lowland (HBL), Canada. Hypotheses and models describe how small-scale feedbacks among vegetation, hydrology, and nutrients cause spatial differenc...

The response of evapotranspiration (ET) to warming is of critical importance to the water and carbon cycle of the boreal biome, a mosaic of land cover types dominated by forests and peatlands. The effect of warming-induced vapour pressure deficit (VPD) increases on boreal ET remains poorly understood because peatlands are not specifically represent...

Northern peatlands have sequestered a huge amount of carbon through exceptionally low microbial activity which is in part attributed to nutrient-poor conditions. However, both microbial dynamics and nutrient cycling and their links to environmental changes have been neglected in most peatland models. To address this issue, we further developed the...

Restoration of peatlands after peat extraction could be a benefit to the climate system. However a multi-year ecosystem-scale assessment of net carbon (C) sequestration is needed. We investigate the climate impact of active peatland restoration (rewetting and revegetating) using a chronosequence of C gas exchange measurements across post-extraction...

Abstract. Current peatland models generally lack dynamic feedback between the plant community structure and the environment, although the vegetation dynamics and ecosystem functioning are tightly linked. Realistic projections of peatland response to climate change requires including vegetation dynamics in ecosystem models. In peatlands, Sphagnum mo...

Ombrotrophic bogs can comprise a mosaic of vegetation patches and open-water pools, with hydrological and biogeochemical connections between pools and the surrounding peat and vegetation. To establish these connections, we studied the spatial heterogeneity of hydrology and water chemistry in two zones of distinct vegetation assemblages in the subbo...

Boreal peatlands store an enormous pool of soil carbon that is dependent upon – and vulnerable to changes in – climate, as well as plant community composition. However, how nutrient availability affects the effects of climate and vegetation change on ecosystem processes in these nutrient-poor ecosystems remains unclear. Here we show that although w...

Peatlands after drainage and extraction are large sources of carbon (C) to the atmosphere. Restoration, through re‐wetting and revegetation, aims to return the C sink function by re‐establishing conditions similar to that of an undrained peatland. However, the time needed to re‐establish C sequestration is not well constrained due to the lack of mu...

Climate change projections show that temperature and precipitation increases can alter the exchange of greenhouse gases between the atmosphere and high latitude landscapes, including their freshwaters. Dissolved organic carbon (DOC) plays an important role in greenhouse gas emissions, but the impact of catchment productivity on DOC release to subar...

ORNL DAAC graphics citation communication. (PDF)

Source data citation aprroval for the vegetation map of Stordalen catchment, Sweden. (PDF)

Guide to attribution of geodata by Lantmäteriet. (PDF)

The Second Warning to Humanity provides a clarion call for wetland researchers and practitioners given the loss and degradation of wetlands, the declining availability of fresh water, and the likely consequences of climate change. A coordinated response and approach to policies has the potential to prevent further degradation and support resilient...

In peatland ecosystems, there are close feedbacks between the dynamics and metabolism of microbial communities and the quality and quantity of organic matters accumulated in peat profiles. However, such feedbacks are poorly described or linked to environmental changes in many peatland models. Here we developed MWCM (McGill Wetland Cohort Microbial...

Peatlands play a fundamental role in climate regulation through their long-term accumulation of atmospheric carbon. Despite their resilience, peatlands are vulnerable to climate change. Remote sensing offers the opportunity to better understand these ecosystems at large spatial scales through time. In this study, we estimated water table depth from...

Peatlands cover a large area in Canada and globally (12% and 3% of the landmass, respectively). These ecosystems play an important role in climate regulation through the sequestration of carbon dioxide from, and the release of methane to, the atmosphere. Monitoring approaches, required to understand the response of peatlands to climate change at la...

Part 1 of this review synthesizes recent research on status and climate vulnerability of freshwater and saltwater wetlands, and their contribution to addressing climate change (carbon cycle, adaptation, resilience). Peatlands and vegetated coastal wetlands are among the most carbon rich sinks on the planet sequestering approximately as much carbon...

The fruticose lichens C ladina stellaris and C ladina rangiferina , form thick mats that can cover large areas of northern peatlands (above c . 50° latitude), including the extensive peatlands of the Hudson Bay Lowland ( HBL ) in Canada, where lichens may cover up to 50% of the landscape. Despite the abundance of lichens in northern peatlands, our...

Litter decomposition, a key process by which recently fixed carbon is lost from ecosystems, is a function of environmental conditions and plant community characteristics. In ice-rich peatlands, permafrost thaw introduces high variability in both abiotic and biotic factors, both of which may affect litter decomposition rates in different ways. Can t...

To quantify CO2 emissions from water surface of a reservoir that was shaped by flooding the boreal landscape, we developed a daily time-step reservoir biogeochemistry model. We calibrated the model using the measured concentrations of dissolved organic and inorganic carbon (C) in a young boreal hydroelectric reservoir, Eastmain-1 (EM-1), in norther...

Background and aimsOrganic matter decomposition in response to thawing permafrost has critical implications for carbon release. This study examined how thaw induced plant community and environmental changes influenced litter and peat decomposition in a subarctic peatland. Methods We conducted laboratory incubations under current site pre-thaw (dry...

Determining the plant traits that best predict carbon (C) storage is increasingly important as global change drivers will affect plant species composition and ecosystem C cycling. Despite the critical role of peatlands in the global C cycle, trait–flux relationships in peatlands are relatively unknown. We assessed the ability of four non‐destructiv...

The renewed growth in atmospheric methane (CH4) since 2007 after a decade of stabilization has drawn much attention to its causes and future trends. Wetlands are the single largest source of atmospheric CH4. Understanding wetland ecosystems and carbon dynamics is critical to the estimation of global CH4 and carbon budgets. After approximately 7 yea...

Dissolved organic carbon (DOC) plays a key role in the peatland carbon balance and serves numerous ecological and chemical functions including acting as a microbial substrate. In this study, we quantify the concentration, biodegradability, and intrinsic properties of DOC obtained from peat, fresh material, and litter from nine species of ombrotroph...

Ombrotrophic bogs are nutrient-poor systems and important carbon (C) sinks yet there remains a dearth of information on the belowground stoichiometry of C, nitrogen (N), phosphorus (P), and potassium (K), important determinants of substrate quality for microorganisms, in these systems. In this study, we quantified the C, N, P, and K concentrations...

Peatlands have been and remain exploited either for agricultural purposes, forestry, peat extraction or infrastructure development in the northern latitudes as well as in the tropics. Modelling current and future carbon exchanges in peatlands thus requires further understanding of carbon dynamics in drained, exploited and restored peatlands. This s...

There is considerable debate on the role of hydroelectric reservoirs for the emission of CO2 and other greenhouse gases. To quantify CO2 emissions from a newly created reservoir that was formed by flooding the boreal landscape we developed a daily time-step reservoir model by integrating a terrestrial and an aquatic ecosystem model. We calibrated t...

The thermal dynamics of human created northern reservoirs (e.g., water temperatures and ice cover dynamics) influence carbon processing and air–water gas exchange. Here, we developed a process-based one-dimensional model (Snow, Ice, WAater, and Sediment: SIWAS) to simulate a full year's surface energy fluxes and thermal dynamics for a moderately la...

Current models and theories of the formation and maintenance of microtopography in ombrotrophic peatlands (bogs) assume autogenic feedbacks between vegetation composition, water table depth (WTD) and microtopography. A hypothesized outcome of autogenic feedbacks is a strong association among spatial variations in vegetation composition, WTD and mic...

Peatlands in discontinuous permafrost regions occur as a mosaic of wetland types, each with variable sensitivity to climate change. Permafrost thaw further increases the spatial heterogeneity in ecosystem structure and function in peatlands. Carbon (C) fluxes are well characterized in end-member thaw stages such as fully intact or fully thawed perm...

Peatland carbon dioxide (CO2) exchange can vary spatially over a few meters because of the heterogeneity in plant communities, differing responses to environmental conditions, and the presence of pools in patterned peatlands. In contrast to the plant communities comprising a peatland’s vegetated surface, permanent pools that are characteristic of p...

Peatlands in discontinuous permafrost regions occur as a mosaic of wetland types, each with variable sensitivity to climate change. Permafrost thaw further increases the spatial heterogeneity in ecosystem structure and function in peatlands. Carbon (C) fluxes are well characterized in end-member thaw stages such as fully intact or fully thawed perm...

Lichen (Cladina stellaris) can be a dominant vegetation cover on bogs within the extensive peatland landscape of the Hudson Bay Lowlands (HBL), northern Ontario, Canada. The unique characteristics of lichens (growth structure and function as a symbiotic organism), their ability to form thick, dense mats across the HBL bogs, and their increased tole...

Significance Wetlands are unique ecosystems because they are in general sinks for carbon dioxide and sources of methane. Their climate footprint therefore depends on the relative sign and magnitude of the land–atmosphere exchange of these two major greenhouse gases. This work presents a synthesis of simultaneous measurements of carbon dioxide and m...

Peatland open-water pools, a common feature on temperate to subarctic peatlands, are sources of carbon (C) to the atmosphere but their contribution to the net ecosystem carbon dioxide exchange (NEE-CO2) is poorly known; there is a question as to whether peatlands with pools are smaller sinks of atmospheric C, or even C-neutral, compared to other pe...

There are still large uncertainties in peatland methane flux dynamics and insufficient understanding of how biogeochemical processes scale to ecosystems. New Zealand bogs differ from Northern Hemisphere ombrotrophic systems in climatic setting, hydrology, and dominant vegetation, offering an opportunity to evaluate our knowledge of peatland methane...

Radiative forcing feedbacks from wetlands have been an important component of past climate change and will likely be so in the future, so accurately assessing the carbon (C) and radiative balances of wetlands remains an important research priority. This commentary shows that the paper by Mitsch et al. (Landscape Ecol 28:583–597, 2013) seriously und...

Ecosystem modelling is a useful tool for gaining insight and quantifying the carbon exchange between the atmosphere and terrestrial ecosystems. This study examines how well Forest-DNDC (a process-based biogeochemical model for forests/wetlands) estimates carbon dioxide (CO2) fluxes from Canadian boreal forests and peatlands. We also evaluate the ap...

The carbon (C) storage of northern peatlands is equivalent to ~34-46% of the ~795 T g C currently held in the atmosphere as CO2. Most studies report that northern peatlands are a sink of between 20 and 60 g CO2-C m-2 yr-1. Since peatland hydrology and biogeochemistry are very closely related to climate, there is concern whether northern peatlands w...

Climate change scenarios suggest that northern peatlands could become drier. To address the type and magnitude of vegetation change associated with persistent drying, we studied changes in biomass and leaf area index following drainage 85 years previously of a bog, using destructive sampling, allometric relationships, and optical measurements. Our...

Ecosystem phenology plays an important role in carbon exchange processes and can be derived from continuous records of carbon dioxide (CO2) exchange data. In this study we examine the potential use of phenological indices for characterizing cumulative annual CO2 exchange in four contrasting northern peatland ecosystems. We used the approach of Jons...

Although temporal and spatial variations in peatland methane (CH4) emissions at broad scales are often related to water table (WT) using a linear relationship, a potentially complex relationship exists between these variables locally and over shorter time scales. To explore this issue, CH4 fluxes were measured using eddy covariance at the Mer Bleue...

We measured CH4 flux at high temporal resolution with triplicate autochambers from three different plant communities at the ombrotrophic Mer Bleue bog in Canada to investigate the spatial and temporal variations, and factors that related to the CH4 flux. Our results show that seasonal mean CH4 fluxes from the Eriophorum-dominated community were 1.4...

Permafrost thaw in peatlands has the potential to alter catchment export of dissolved organic carbon (DOC) and thus influence downstream aquatic C cycling. Subarctic peatlands are often mosaics of different peatland types, where permafrost conditions regulate the hydrological setting of each type. We show that hydrological setting is key to observe...

[1] While peatland ecosystems overall are long-term net carbon (C) sinks, the open-water pools that are characteristic of boreal peatlands have been found to be C sources to the atmosphere. However, the contribution of these pools to the ecosystem level C budget is often ignored even if they cover a significant area of the peatland surface. Here we...

Long-term impacts of drier conditions on the hydrology of northern peatlands are poorly understood. We used long-term drainage near a historic drainage ditch, separating an area from the main peatland, as an analogue for long-term drying in a northern temperate bog. The objective was to identify the impact of drier conditions on ecohydrological pro...

About 0.3 million km2 of boreal forests and peatlands and their soils have been flooded through the creation of hydroelectric reservoirs. To establish the effect of flooding on dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) production, we incubated six sample types of boreal forest and peatland soils and litters for 15 weeks unde...