Nigel Roulet

My major areas of interest are ecohydrology, catchment biogeochemistry and ecosystem functions.

B.Sc., M.Sc. Trent University; Ph.D. McMaster University

James McGill Professor, Department of Geography
Member, Global Environment and Climate Change Centre [GEC3]
Former Director, McGill School of Environment
Friend of the Tree Canada Foundation

Welcome to my home page. I have prepared this page for undergraduates, prospective graduate students and post-doctoral research associates, for others who have similar interests to mine. I have divided my home page into five sections as listed on the left.

Keywords: integration of climate, hydrology, biogeochemical cycles and functional ecology; ecohydrology; carbon and methane fluxes from northern ecosystems; environmental systems modelling

After looking over my page if you have any questions please do not hesitate to contact me either by e-mail or telephone.

Contact:
Department of Geography
McGill University,
805 Sherbrooke Street West,
Montreal, QC H3A 2K6
Canada

Telephone:
514-398-4945 (Geography)
514-398-3759 (C2GCR)

Facsimile:
514-398-7437 (Geography)
514-398- 1381 (C2GCR)
Email: nigel.roulet [at] mcgill.ca

nigel.roulet [at] mcgill.ca (E-mail)

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Research Focus

The research conducted in my group is at the interface among hydrological, climatological, biogeochemical, and ecological systems. I am interested in understanding how biogeochemical transformations and ecosystem dynamics respond to changes in hydrological and climatological settings and forcings. My work broadly fits under the umbrella of earth system science, biogeochemistry and ecohydrology. I employ observational, experimental, and modelling approaches to help us resolve fundamental questions related to process and pattern. Geographically the ecosystems attracting my current interest are located in the cool-temperate, boreal, subarctic and arctic ecoclimatic regions. The ecosystems of focus are wetlands, particularly peatlands, and forests. I conduct research in North America and Europe.

At the present time the primary foci of my research are a) the couplings among climate, hydrology and the biogeochemistry of northern wetland ecosystems, particularly the measurement and modelling of the role of peatland ecosystems in the global carbon and methane cycles, comprising three tightly linked studies on measurement and process studies of Fluxnet-Canada, modelling of the carbon dynamics of peatlands from the scale of individual peatlands to a global wetland model, and the determination of baseline greenhouse gas exchanges for peatlands in the James Bay region of Quebec; and b) the runoff hydrology and biogeochemistry of forested and wetland catchments, particularly the role the hydrological pathways play in the transport and transformation of biogeochemically important species. Currently we are examining how role catchment size and topography influence runoff response and biogeochemical export in relative steep, forested catchments.

I the brief outlines below I have included the names, in parentheses, of the undergraduate and graduate students, post-doctoral fellows, and research associates who are working with me.
 

The Carbon Exchange In Northern Peatlands

Measurements and processes of the cycling of carbon and methane in wetlands as part of the Fluxnet Canada Research Network

In 1996 we started a research project called the Peatland Carbon Study (PCARS). This project has three objectives: 1) to measure the exchange of carbon between peat covered wetlands and the atmosphere and adjacent ecosystems with sufficient accuracy to determine the daily, seasonal, and inter-annual variability in exchanges; 2) to understand through plot, laboratory, and observational studies the processes that control internal cycling and exchanges; and 3) to develop process based models of the carbon dynamics of peatland ecosystems that can be used to simulate the variability of carbon exchanges over short (yearly to a century) and long (decades to millennia) time scales. PCARS is continuing beyond its original five years now as part of the Fluxnet-Canada Research Network (FCRN), which is funded by a NSERC Research Network grant, a Canadian Foundation for Climate and Atmospheric Studies (CFCAS) network grant, and BIOCAP Canada. The measurement and experimental aspects of this research are outline in this following section while the modelling effort is discussed in the next section.

PCARS is a collaboration among Dr. Peter Lafleur (Trent U.; micrometeorology and atmospheric - surface exchanges using eddy covariance techniques), Dr. Pierre Richard (U. du Montréal; palaeo-reconstruction of the carbon accumulation of the past), Dr. Tim Moore (Geography, McGill; ecosystem processes and biogeochemistry), and me (process level carbon exchanges, whole ecosystem carbon dynamics, modelling, and hydrology).

PCARS is built around the continuous carbon flux measurement program at the Mer Bleue bog, a 28 km2 peatland, located just east of Ottawa, Ontario (see a LANDSAT image and beautiful photographs by Robert Williams of the Mer Bleue bog). Mer Bleue, while located in the cool-temperate ecoclimatic region, is more representative of raised shrub bogs of the boreal region. Peat began accumulating at Mer Bleue approximately 8.5 kBP, and the ecosystem became a bog at approximately 6.0 kBP. Most of Mer Bleue has between 4.0 to 5.5 m of peat.

Some of the question I am currently interested in answering with our measurement and experimental program are:

What is the affect of nitrogen deposition on the cycling of N in Mer Bleue and what is the relative importance of the export of dissolved inorganic and organic nitrogen (Jean Rattle, M.Sc. candidate)?

What is the spatial variability in the ecosystem level exchanges within the same peatland and among different peatlands and wetlands in the same ecoclimatic and geographical region?

What is the exchange of CO2 and CH4 between constructed and restored wetlands and the atmosphere and how does this exchange compare to the exchanges that occur in natural wetlands?

How does environmental change induce changes in structure of the vegetation community and how do those changes, in turn, alter the biogeochemical cycling in Mer Bleue (Julie Talbot, PhD candidate)?

For examples of this work see Fraser & Roulet (200); Fraser et al. (2001); Lafleur et al. (2001); Lafleur et al. (2003); and Moore et al. (2001) below.

 

Modelling the development and carbon dynamics of peatlands

Parallel with the empirical studies of the PCARS we have developed, and continue to further develop, several models that couple the carbon dynamics of peatlands to hydrology, nutrients, and climate.

The Peatland Carbon Simulator: The first model, referred to as the Peatland Carbon Simulator (PCARS - note the same acronym as the study!), is a process level model that simulates climate - peatland interactions at time scales relevant for climate change - e.g. 50 to 100 years. The PCARS model was largely developed by Dr. Steve Frolking (Complex Systems, Institute for the Study of Earth Ocean and Space, University of New Hampshire) in collaboration with the PCARS field studies. We have parameterized the Canadian Land Surface Scheme (CLASS) for peatland hydrology and we have now coupled PCARS and CLASS. The model can run free-standing or coupled to a local climate model. With this model combination will are examining the sensitivity of the annual carbon dynamics to climate variability and change. The approach we (Dr. Bing Ouyang and I) are using at present comprises:

the determination of the inter-annual variability in the peatland carbon exchange due to climate variability;

and the estimation of the potential change in carbon storage and flux between 1 x CO2 and 2 x CO2 climate scenarios.

For examples of this work see Comer et al. (2000), Frolking et al. (2001); Frolking et al. (2003), and Letts et al. (2000).

The Peat Accumulation Model (PAM): We have developed a second model, the Peat Accumulation Model (PAM), a more phenomenological model to address questions about the long-term variability (decades to millennia) in carbon accumulation in peatlands. We initially developed PAM in collaboration with Dr. David Hilbert (Tropical Forest Research, CSIRO Atherton, Australia). PAM is the first model that couples the water balance and peat accumulation in a long-term simulation of peatland development. The results of this initial work are extremely interesting and indicated the potential for using PAM to explore some of the basic theoretical questions concerning peatland development. We are currently comparing the palaeo-reconstructed carbon accumulation over the last 8.5 k years for Mer Bleue with the simulated accumulation using PAM driven with palaeo-precipitation. We have just begun to develop a simple 2-d version of PAM that can mimic aspects of the development of the patterns commonly seen on northern peatlands - i.e. hummock/hollows, and at a larger scale pools, ridges and flarks. PAM also suggests some avenues for exploring how and why some fens change to bogs over time, while others do not. Currently we are using PAM in conjunction to address the following questions:

 What controls the development of hummocks and hollows, and pools and ridge on the surface of raised bogs and mineral poor fens (Nicola McEnroe, PhD candidate)?

What controls the transition for mineral poor fens to ombrotrophic bogs?,

Can the variability in the long-term rates of carbon accumulation be explained by variations in moisture storage; and

What kinds of disturbance will lead to significant changes in peat accumulation - e.g. fire, permafrost collapse?

For an example of this work see Hilbert et al. (2000).

The New Peatland Model (NPM): Under the auspices of the CFCAS supported Canadian Global Coupled Climate Carbon model (CGC3M) research network we are developing a simpler wetland model for global simulations. The CGC3M network is developing a global terrestrial ecosystem model and a global ocean chemistry and biology model for inclusion in the CCCma-GCM. The CGC3M network is a collaboration of five universities (McGill, McMaster, Alberta, UBC, Victoria) and two federal government departments (Environment Canada, the Canadian Centre for Climate Modelling and Analysis, and Fisheries and Oceans, Institute of Ocean Sciences). Our specific efforts at McGill University are to take the knowledge we learned in developing PCARS and PAM to develop a global wetland model suitable for global simulations. The challenge is to make the model remains true enough to capture the core dynamics of the links between climate and the carbon cycle but is as computationally efficient as possible. We are proceeding along the following steps:

Compare the simulated distribution against the wetland data sets generated by the IGBP-DIS wetland project (JW) ;

In the simulations estimate the position of the water table using the dynamic hydrology of northern and southern wetlands generated by the wetland parameterization in CLASS (FSH, JW & BO); and

Simulate the wetland-climate feedback for CO2 and CH4 with coupled runs of the GCM.

Measurement and modelling of the carbon dynamics of subarctic peatlands in the James Bay region

In many areas of northern Canada terrestrial ecosystems are being inundated by large reservoirs created for the production of hydroelectricity. Studies have shown that these reservoirs can emit CO2 and CH4. To assess the net impact of the creation of reservoirs on the emission of greenhouse gases the net carbon exchange of the ecosystems prior to flooding needs to be hindcast. To estimate the emission for peatlands in the James Bay region we are measuring and modelling the NEE and CH4 exchange on three peatland complexes situated 30, 120 and 250 km inland from the east coast of James Bay. Based on the observations, we will parameterize and initialize PCARS to simulate the exchange over the larger region. For this we are relying on remote sensing analysis of peatland distribution. We will then use climate data from the region as inputs to simulate the annual exchanges for peatlands, thus providing a baseline against which the emissions from reservoirs can be assessed. This work is being done as part of a NSERC Collaborative Research Development grant to Drs. Michelle Garneau, Principal Investigator (UQAM), Pierre Richard (UdeM), Tim Moore (Geography, McGill University), Monique Bernier (INRS Terre et Environement) and Hydro-Quebec.

For examples of similar studies see Dove et al. (2000); Roulet (2000): Roulet et al. (1994) and Roulet et al. (1997)

Role of Hydrological Pathways and Catchment Size in the Export of Biogeochemically Important Species from Forested Catchments

April James, a Ph.D. student of mine, and I are studying how catchment size influences the dominant flow pathways, and consequently affects the timing and magnitude of chemical export. We have instrumented seven nested catchments in the Gault Nature Reserve on Mont St. Hilaire. We are monitoring runoff response, isotopic signatures, and the change in chemical concentrations at the outflow of the catchments. We have also instrumented two of the catchments to examine how the temporal and spatial changes in soil moisture storage and its spatial organization (disorganization) and connectivity explain the runoff response and biogeochemical transformations and transport. We plan to explore how scale and thresholds can be incorporated into implicit runoff models such as TOPMODEL.

The basic hydrology and research on runoff mechanisms have been studied and we are continuing this work by concentrating on the movement and transformation of dissolved inorganic and organic nitrogen through the catchments (Guillaume Couillard, M.Sc. candidate).

For examples of similar studies see Branfireun & Roulet (2002), Allan et al. (2001), Branfireun et al. (2000), and Quinton and Roulet (1998).

Current opportunities for graduate and post-doctoral studies

There are lots of opportunities for graduate students and post-doctoral research fellows to work on within my research program. The Department of Geography offers both a M.Sc. and a Ph.D. in physical geography. The program has developed specializations in climate and global change and ecosystem biogeochemistry and hydrology. In addition to the programs in Geography there are a number of allied programs in Atmosphere and Ocean Sciences and the Faculty of Agricultural and Environmental Sciences on the Macdonald Campus of McGill University. McGill University is also home to a number of interdisciplinary research centres such as the Global Environment and Climate Change Centre (GEC3). GEC3 greatly enhances the graduate experience by exposing students to a much broader range of ideas and fields than would normally occur in a disciplinary base program.

For information on the graduate program in the Department of Geography please see: Graduate Information

Graduate students in our program normally receive between $16,000 to $19,000 per year of support from a combination of research and teaching assistantships, stipends and external and internal scholarships. In addition to Departmental support and support directly from supervisors there are a number of funding opportunities for graduate students through the Faculty of Graduate Studies. For new students applying to McGill University the Tomlinson Graduate Fellowships are particularly attractive but one has to apply early. We encourage prospective students who have a good GPA to pursue NSERC and FCAR post-graduate scholarships.

If you are interested in any of the research outlined above or other aspects of the links among hydrology, climate, biogeochemistry and ecosystems do not hesitate to contact me. I recommend you contact me early in the fall semester. For prospective students who are located in north eastern North America I encourage to come and visit. During a visit we can discuss your ambitions and expectations regarding graduate studies and you can meet other members of the department and C2GCR where appropriate, but more importantly you can meet some of current graduate students, who can give you the inside view on our program. I have listed below some of my former and current present graduate students. For some of my past students I have included a link to their home page when I know it and for my current students can contact them directly via e-mail via the graduate student page on the Department of Geography website.

Current Graduate Students (see Dept list)

Kim, Young Il (2006) Ph.D (Roulet) Carbon gas fluxes from natural boreal forests and peatlands and new built reservoir

Lai, Derrick (2007) Ph.D. (Roulet and Moore) Greenhouse gas dynamics in natural, restored and created wetlands

Olefeldt, David (2006) Ph.D. (Roulet)

Wilson, Paul (2009) M.Sc. Roulet. Hydrologic Pathways and Carbon Cycling in Northern Peatlands.

Jianghua Wu (PhD.): working on global wetland, hydrological and carbon modelling

Current Post Doctoral Fellows and Research Associates

Dr. Bing Ouyang - working on coupling peatland carbon models to climate models

Former Graduate Students

Dr. Craig Allen (PhD, York University, 1993) - now Associate Professor, Department of Geography and Earth Sciences, University of North Carolina, Charlotte NC

Dr. Mike Waddington (M.Sc., 1990; PhD, York University, 1994) - now Associate Professor of the School of Geography and Geology, McMaster University, Hamilton ON.

Dr. Matthew Letts (M.Sc., McGill University, 1998; Ph.D. King's College, University of London 2003) - now Assistant Professor, Department of Geography at the University of Lethbridge, Alberta.

Alice Dove (M.Sc., McGill University, 1996) - now an environmental scientist with Environment Canada, Burlington Ontario.

Dr. William Quinton (M.Sc., York University; PhD 1989; University of Saskatchewan, 1995) - now Assistant Professor, Department of Geography, Simon Fraser University, Burnaby, BC.

Dr. Brain Branfireun (M.Sc., York University, 1994; Ph.D. McGill University, 1998) - now Associate Professor, Department of Geography, University of Toronto.

Dr. Neil Comer (M.Sc., 1992, Ph.D., 2000, McGill University) - now a research scientist with Environment Canada, Ontario Climate Centre, Toronto, Ontario.

Colin Fraser (M.Sc., 1999) - now a research scientists with the Alberta Research Council.

Julian Cleary (M.Sc., 2003) – now an environmental consultant and about to begin a PhD at the University of Toronto.

Dr. Charlotte Roehm (Ph.D., McGill University, 2003) - now a post doctoral fellow in limnology at UQAM, Montreal, QC.

Kathleen Lysyshyn (M.Sc., McGill University, 2000) - now working for Natural Resources Canada on climate change and carbon sequestration issues.

Former Post Doctoral Fellows and Research Associates

Dr. David Hilbert: When David was here he developed the first version of the Peatland Accumulation Model.  He is now at the CSIRO Tropical Research Centre in Atherton, Queensland, Australia.

Dr. Jukka Turunen: When Jukka was here he worked on the carbon accumulation in peatlands and its relation to nitrogen deposition. He now is a research scientist with the Finnish Geological Survey and a research professor with the University of Kuopio, Finland.

Teaching

I teach both undergraduate and graduate courses in the Department of Geography and the McGill School of Environment (MSE).

ENVR 200 The Global Environment: I am one of four instructors (Professors Stewart [Atmosphere and Ocean Sciences]; Ricciardi [MSE and Redpath Museum]; Green [Economics]) in this team taught, introductory core course of the MSE undergraduate program. This course introduces the central concepts of earth system science and we use climate change, the global water and carbon cycles, and species invasion as the primary environmental issues to structure the arguments. My contributions include an introduction to global scale environmental system, how global biogeochemical cycles and climate vary over time scales (billions of years, million of year, and over the last two centuries), and how the activities of humans have biogeochemical cycles and possibly climate. I have designed two computer simulations to help reinforce the material taught in lectures. The first simulation deals with some basic concepts of systems theory illustrated with a simplified version of Lovelock and Watson’s Daisy World model and the second simulation analyzes the fate anthropogenic emissions of CO2 in the global carbon cycle.

GEOG 322 Environmental Hydrology: This is my third course in hydrology. It is a required course for the B.Sc. Geography and the B.Sc. water domain of the MSE. In the first half of the course deals with the components of the hydrological cycle - i.e. precipitation, snowmelt, evapotranspiration, and soil and groundwater, initially at the global scale but mostly at the scale of individual river or stream catchments. The components are then integrated to attain a general theory of catchment runoff. In the last part of the course we attempt to define water as a renewable resource and then look at how humans have modified the hydrological cycle. This course combines lectures, several take home assignments, and the researching and writing of a major research paper as learning tools. Depending on weather conditions (the course is usually in the winter term) I attempt to organize a visit to our research catchments at the Gault Nature Reserve on Mont Saint Hilaire.

GEOG 501 Modelling Environmental Systems: This is my advanced undergraduate/graduate course on modelling environmental systems. The course begins with a few lectures on modelling theory and applications, but the majority of the structured instruction takes place in the computer laboratory where students interactively learn about the basic archetypes of systems model. There are several small exercises to progressively develop basic skills in modelling. The last third of the course is dedicated to the development of model to simulate an environmental system. The first model is developed in a group and focus on one environmental problem and then each student develops a model to simulate the environmental system of her/his choice. In this course we use Stella so no prior programming experience is needed.

GEOG 505 Global Biogeochemical Cycles:  This is an advanced undergraduate/graduate course that Professor Tim Moore and I offer. In first section of the course examines the biogeochemical cycling of important elements and compounds at the scale of hydrological catchments, and we are currently use nitrogen as our example element. The second section changes scale to look at global carbon cycle. The course is built around tutorial where we discuss key paper in biogeochemistry. Students, in groups of four to five, have to assess the magnitude the main stores and fluxes of the global cycle of one main biogeochemical constituent. In addition each student is required to research and write a paper on a topic of their choice related to biogeochemical cycling. This course places emphasis on developing the skill of critical analyzing research papers and the presentation of that analysis to your colleagues in a seminar format.
 

Publications

Recent Papers in Refereed Journals (* with graduate students, post-doctoral fellows and research associates)

Basiliko, N., T.R Moore, P.M. Lafleur, and N.T Roulet. Seasonal and inter-annual decomposition, microbial biomass, and nitrogen dynamics in a Canadian bog. Soil Science (in press). *

Wang, Y., L.A.M. Mysak, and N.T. Roulet. Holocene climate and carbon dynamics: Experiments with the “green” McGill Paleoclimate Model. Global Biogeochemical Cycles 2005GB002484, 2005 (in press). *

Letts, M., P.M. Lafleur, and N.T. Roulet. On the relationship between cloudiness and net ecosystem carbon dioxide exchange in s peatland ecosystem. Ecoscience 12:53-59, 2005.*

Lafleur, P.M., R.A. Hember, S.W. Admiral and N.T. Roulet. Annual and seasonal variability in evapotranspiration and water table at a shrub-covered bog. Hydrological Processes (in press)

J. Turunen, N.T. Roulet, T. R. Moore, and P.J.H. Richard. Nitrogen deposition and increased carbon accumulation in ombrotrophic peatlands in eastern Canada. Global Biogeochemical Cycles 18: GB3002, doi:10.1029/2003GB002145, 2004.*

Cleary, J., N.T. Roulet and T.R. Moore. Greenhouse gas emissions from Canadian peat extraction, 1990-2000: A life cycle analysis. Ambio (in press), 2004.*

Lafleur, P.M., T.R. Moore, N.T. Roulet, and S. Frolking. Dependency of ecosystem respiration in a cool temperate bog on peat temperature and water table. Ecosystems 2005.

Moore, T.R, C. Blodau, J. Turunen, and N. Roulet. N and S accumulation in bogs. Global Change Biology 11, 356–367, doi: 10.1111/j.1365-2486.2004.00882, 2004.

Roehm. C. L., and N.T. Roulet. The seasonal contribution of CO2 fluxes in the annual C budget of a northern bog. Global Biogeochemical Cycles 17:(1), 2002GB001889, 2003.*

Moore , T.R., Matos, L., and N.T. Roulet. Dynamics and chemistry of dissolved organic carbon in Precambrian shield catchments and an impounded wetland. Canadian J. Fisheries and Aquatic Sciences (in press).

Lafleur, P.M., Roulet, N.T., Bubier, J.L., Frolking, S., and T.R. Moore. Interannual Variability in the Peatland-Atmosphere Carbon Dioxide Exchange at an Ombrotrophic Bog. Global Biogeochemical Cycles 2002 GB001963, 2003.

Bubier, J.L., G. Bhatia, T.R. Moore, N.T. Roulet and P.M. Lafleur, Between year and site variability in growing season net ecosystem CO2 exchange controlled by respiration at a large peatland, Ontario, Canada. Ecosystems (in press).

Wilsey, B.J., G. Parent, N.T. Roulet, T.R. Moore, and C. Potvin. Tropical pasture carbon cycling: relationships between C source/sink strength, above-ground biomass and grazing. Ecology Letters 5: 367-376, 2002 *

Branfireun, B.A., and N.T. Roulet. The boreal catchment hydrological cascade: controls on the fate and transport of methylmercury. Hydrology and Earth Ssystem Sciences 6:785-794, 2002 *

Grant, R., N.T. Roulet, and P. Crill, Methane efflux from boreal wetlands: theory and evaluating the ecosystem model ecosys with chamber and tower flux measurements, Global Biogeochemical Cycles 16(4) 2001GB001702, 2002.

Frolking, S., N.T. Roulet, T.R. Moore, P.M. Lafleur, J.L. Bubier and P.M. Crill. Modeling the seasonal and annual carbon balance of Mer Bleue bog, Ontario, Canada. Global Biogeochemical Cycles 16:(3) 2001GB001457, 2002.

McBean, G., A. Weaver, and N.T. Roulet. The Science of Climate Change. ISUMA: Canadian Journal of PolicyResearch 2:16-25, 2001.

Frolking, S., N.T. Roulet, T.R.Moore, P.J.H. Richard and M. Lavoie. Modeling northern peatland decomposition and peat accumulation. Ecosystems 4:479-498, 2001.

Moore, T.R., J. Bubier, S. Frolking, P. Lafleur, and N. Roulet. Plant biomass and production and CO2 exchange in an ombrotrophic bog. Journal of Ecology. 90: 25-36, 2002.

Edwards, G.C., G.M. Dias, G.W. Thurtell, G.E. Kidd, N.T. Roulet, C.A. Kelly, J.W.M. Ridd, A. Moore, and L. Halfpenny-Mitchell. The measurement of methane flux from a natural wetland pond and adjacent vegetated wetlands using a TDL-based flux-gradient technique. Water, Air, and Soil Poll. (in press).

Allan C.A., A. Heyes, N.T. Roulet, V. St. Louis and J. Rudd. Spatial and temporal dynamics of mercury in Precambrian Shield upland runoff. Biogeochemistry.52:13-40, 2001.

Chapin, F.S., III, A.D. McGuire, J. Randerson, R. Pielke, Sr., D. Baldocchi, S.E. Hobbie, N. Roulet, W. Eugster, E. Kasischke, E.B. Rastetter, S.A. Zimov, and S.W. Running. Arctic and boreal ecosystems of western North America as components of the climate system. Global Change Biology, 6 Suppl. 1: 211-223, 2001.

Fraser, C. and N.T. Roulet. Groundwater flow patterns in a large peatland. Journal of Hydrology, 246: 142-154, 2001 *

Fraser, C., N.T. Roulet, and T.R. Moore. Hydrology and dissolved organic carbon biogeochemistry in a large peatland. Hydrological Processes 15:3151-3166, 2001. *

Branfireun, B., K. Bishop, N. Roulet, M. Nilsson, and G. Granberg. Mercury cycling in boreal ecosystems: The long-term effect of acid rain constituents on peatland pore water methylmercury concentrations. Geophysical Research Letters 28: 1227-1230, 2001. *

Lafleur, P.M., N.T. Roulet, and S. Admiral. The annual cycle of CO2 exchange at a boreal bog peatland. Journal of Geophysical Research 106(D3): 3071-3081, 2001.

Roulet, N.T. Peatlands, Carbon Storage, Greenhouse Gases and the Kyoto Protocol: Prospects and Significance for Canada. Wetlands 20: 605-615, 2000.

Bassard, P., J.M. Waddington, A.R. Hill, and N.T. Roulet. Modelling groundwater - surface water mixing in a headwater wetland: implications for hydrograph separation. Hydrologival Processes 14:2697-2710, 2000.

Waddington, M.J., and N.T. Roulet. Carbon balance of a boreal patterned peatland. Global Change Biology 6: 87-97, 2000. *

Branferiun, B.A., N.T. Roulet, C.A. Kelly, and J.W.M. Rudd. In situ stimulation of mercury methylation in a boreal peatland: towards a link between acid rain and methylmercury contamination in remote environments. Global Biogeochemical Cycles 13: 737-742, 1999. *

Hilbert, D.W., N.T. Roulet, and T.R. Moore. Modelling and Analysis of Peatlands as Dynamic Systems. Journal of Ecology 88:241-256, 2000. *

Letts. M.G., N.T. Roulet, N.T. Comer, M.R. Skarupa, and D.L. Verseghy. Parameterization of peatland hydraulic properties for the Canadian Land Surface Scheme. Atmosphere - Oceans 38:141-160, 2000. *

Comer, N.T., P. Lafleur, N.T. Roulet, M.G. Letts, M.R. Skarupa, and D.L. Verseghy. The use of CLASS to model energy balance and soil climate of northern peatlands. Atmosphere - Oceans 38: 161-179, 2000. *

Rivers, J.S., D.I.Siegel, L.S. Chasar, J.P. Chanton, P.H. Glaser, N.T. Roulet, and J.M. McKenzie. A stochastic appraisal of the annual carbon budget of a large circumboreal peatland, Rapid River Watershed, northern Minnesota. Global Biogeochemical Cycles 12: 715-727, 1998.

Dove, A., N.T. Roulet, P. Crill, J. Chanton, and R. Bourbornierre. CH4 dynamics in a boreal beaver pond. Ecoscience 6: 577-586, 1999. *

Quinton, W., and N.T. Roulet. The spring and summer hydrology of the northern patterned fen. Arctic and Alpine Research 30:285-294, 1998. *

Moore, T.R., N.T. Roulet, and J.M. Waddington. Uncertainty in predicting the effect of climate change on the carbon cycling of Canadian peatlands. Climatic Change 40:229-245, 1998.

Frolking, S.E., J.L. Bubier, T.R. Moore, T. Ball, L.M. Bellisario, A. Bhardwaj, P. Carrol, P.M. Crill, P.M. Lafleur, J.H. McCaughy, N.T. Roulet, A.E. Suyker, S.B. Verma, M.J. Waddington, and G.J. Whiting. Relationship between ecosystem productivity and photosynthetically-active radiation for northern peatlands. Global Biogeochemical Cycles 12:115-126, 1998.

Branfireun, B.A., D. Hilbert, and N.T. Roulet. Sources and sinks for methylmercury in Precambrian drainage basins. Biogeochemistry, 41: 277-291, 1998*

Recent Book Chapters

Gitay, H., Brown, S., Easterling, W., Jallow, B., Antle, J., Apps, M., Beamish, R., Chapin, T., Cramer, W., Frangi, J., Laine, J., Lin Erda, Magnuson, J., Noble, I., Price, J., Prowse, T., Root, T., Schulze, E., Sirotenko, O., Sohngen, B., Soussana, J., Buggman, H., Egorov, C., Finlayson, M., Fleming, R., Fraser, W., Hahn, L., Hall, K., Howden, M., Hutchins, M., Ingram, J., Ju Hui, Masters, G., Megonigal, P., Morgan, J., Myers, N., Neilson, R., Page, S., Parmesan, C., Rieley, J., Roulet, N., Takle, G., van Minnen, J., Williams, D., Williamson, T., Wilson, K., Fischlin, A. & Diaz, S. 2001. Ecosystems and their goods and services. In. McCarthy, J.J., Canziani, O.F., Leary, N.A., Dokken, D.J. & White, K.S. (Eds.) Climate change 2001, Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge. pp. 235-342.

Sampson, R. N., R.J. Scholes, C. Cerri, L. Erda, D.O. Hall, M. Hanada, P. Hill, M. Howden, H. Jansen, J. Kimble, R. Lal, G. Marland, K. Minami, K. Paustian, P.A. Sanchez, C. Scoppa, B. Solberg, S. Trumobre, O.Van Cleemput, A. Whitmore, B. Burrows, G. Liping, W. Hall, W. Kaegi, P. Reyenga, N. Roulet, K.E. Skog, G.R. Smith, Y. Wang, and J.W.B. Stewart (1999). Additional Human-Induced Activities - Article 3.4. In The Intergovernmental Panel of Climate Change Special Report on Land Use, Land-Use Change, and Forestry 2000. R. T. Watson, I.R. Noble, B. Bolin, N.H. Ravindranath, D.J. verado, and D.J. Dokken (eds). Cambridge, UK, Cambridge University Press: 375.