Climatology at Trent University
The Blue Lab
Mer Bleue - Eastern Peatland

Auto-chamber system at Mer Bleue

 

 

Peatland Carbon Study (PCARS): Measurement and Modelling of the Contemporary Carbon Sequestration in Peatlands.

FCRN.AGM07.Lafleur.v3.ppt

 

Introduction
Northern peatlands have accumulated between 300 and 500 Pg C (or one third of the carbon stored in soils) since the end of the Wisconsin Ice Age (Gorham 1991; Turunen et al. 2002). At present, peatlands are characteristically found in lowland areas and exhibit moist and nutrient-poor conditions. This leads to an annual carbon balance that is small compared with other terrestrial

environments, yet the sensitivity of peatlands to climate change is of great interest due to their potential ability to act as an atmospheric source of greenhouse gases such as CO2 and CH4. The sequestration of carbon in peatlands is dependent on the balance between photosynthesis, autotrophic respiration and heterotrophic respiration. Each of which involve a number of controlling environmental and climatological processes, making the peatland carbon balance a complex area of study. Varying moisture conditions can strongly influence soil temperature and the proportion of aerobic and anaerobic respiration within peatlands. At water saturation the by-product of anaerobic decomposition, CH4, is produced and can be emitted in large quantities, while drier conditions promote aerobic respiration from plant and microbial biomass. Meanwhile, plants counteract these atmospheric sources of carbon by sequestering carbon dioxide and releasing it to the peat complex as litter. Since most of the peatlands are located in the circumpolar north, a region that is predicted to experience large changes in temperature and precipitation in 2xCO2 scenarios (Cubasch et al. 2001), the effect of climate change on the peatland carbon balance is of concern.

To investigate the response of northern peatlands to climate change the Peatland Carbon Study (PCARS) was initiated in 1997 to measure and model the influence of climate on the carbon balance of a peatland. Since that time the PCARS investigators have collaborated to integrate Mer Bleue into the Fluxnet-Canada Research Network as the Eastern Peatland site. This has provided a number of benefits including financial support, expansion of measurements, interaction among researchers and across disciplines and rigorous testing and intercomparison of data collection and analyses.

There are four main activities at the Mer Bleue site: (1) the development of an ecosystem model for peatlands that explicitly includes aerobic and anaerobic decomposition processes; (2) the coupling of the ecosystem model to the Canadian Land Surface Scheme (CLASS) which has been parameterized to estimate the soil climate of peatlands; (3) the examination of the short-term and long-term carbon accumulation rate of peat accumulation, and how the rate varies with changes in past climate; and (4) through simulations derived from the coupled ecosystem – climate model determine the sensitivity of the peatland carbon pool to climate change and variability.

Study Site
The principal PCARS research site is Mer Bleue, a 35 km2 ombrotrophic bog located 10 km east of the city of Ottawa in the Ottawa River valley. The central portion of the peatland started to form about 8400 years ago accumulating Peat nearly 6 m deep. The porewater at Mer Bleue is highly acidic, rich in dissolved organic carbonb and poor in nutrients. The surface is slightly domed. Vegetation on the surface is composed of ericaceous shrubs (dominantly Chamaedaphne calyculata, Kalmia angustifolia, and Ledum groenlandicum) and grasses. The hummocks are covered by Sphagnum moss (dominantly Sphagnum capillifolium and Sphagnum fuscum) while the hollows are covered by Smilacina trifolia, Eriophorum vaginatum and Sphagnum magellannicum and Sphagnum angustifolium. The instrument tower is located in the western end of the bog, about 250 m from the shore in a northwesterly direction. Instrumentation includes a full suite of meteorological and flux measurements, including energy balance and carbon dioxide. Tower measurements are supported by a number of on-going field investigations on biomass quantification and decomposition, soil water content, hydrology of the bog, and others. A more detailed description of the instruments and measurements is provided on the FCRN website and at Ameriflux.

Recent Developments
The net ecosystem exchange of carbon dioxide (NEE) and its relationship to light varies significantly between peatland types such as bogs, poor fens and rich fens (Frolking et al. 1998). Consequently, the sensitivity of annual peatland C budgets to climate variations is also expected to vary between peatland types. In order to predict the potential consequences of climate change on the large stores of C within northern peatlands, it is critical to understand the biophysical factors, which control respiration, photosynthesis, and aerobic and anaerobic oxidation of peat. By measuring NEE in different peatland types within the same ecoclimatic region, differences in ecosystem structure and function may be evaluated. Ultimately, measurements such as these are critical for the further development and validation of process-oriented C budget models such as the Peatland Carbon Simulator (PCARS) (Frolking et al. 2002).

Using the eddy covariance technique, NEE and evaporation have been continuously monitored since 1998 at the Mer Bleue peatland. Over this period, this bog has been found to be a sink for CO2 of about 70 g C m-2 y-1 (Lafleur et al. 2001). However, remote-sensing imagery shows marked variation in surface vegetation within the Mer Bleue bog and chamber measurements of NEE vary with location.


The objectives of this study begun in 2004 are 1) to quantify the spatial variation of daily and seasonal NEE within the Mer Bleue peatland and between peatlands of different types and 2) to identify the processes and the biophysical factors controlling these variations. The main tower in the Mer Bleue bog is the permanent research site where NEE and water vapour and energy fluxes are continuously measured using the eddy covariance technique. Three additional sites have been established within the Mer Bleue bog but outside of the current flux footprint. These include a cattail marsh, a poor fen, and an ombrotrophic bog with a different composition of species from that of the main tower’s flux footprint. All sites are outfitted with a basic weather station and sensors monitoring microclimate conditions while a mobile eddy covariance system is moved to one of the three satellite sites every 1 to 1.5 months. Fluxes of methane and input/outputs of dissolved organic and inorganic carbon are measured in co-operation with collaborating researchers. At each site, peatland characteristics required for PCARS simulations are also collected. This work will contribute to the development of the PCARS model and its ability to assess the sensitivity of northern peatland C budgets to climate and land-use change.


Other Studies
Wetlands have been a major focus of research at the Blue Lab. Dr. Peter Lafleur has been involved in research at a number of wetlands in Canada (apart from Mer Bleue), including sites at Kesagami River on James Bay, BOREAS FEN site at Thompson, Manitoba, the Peace-Athabasca Delta in northern Alberta, and Cape Race on Newfoundland. The focus of most of this research has been the study of energy and water balances of these wetland ecosystems. Information from many of these sites was used in the CLASS project for validation of this land surface process model for wetlands. Here are some links to other active investigators of the PCARS project:

Dr. Elyn Humphreys, Associate Professor, Carleton University
Website: http://http-server.carleton.ca/~erhumphr/Site/Welcome.html

Dr. Tim Moore, Professor, McGill University
Website: https://www.mcgill.ca/geography/people/moore

Dr. Nigel T. Roulet, Professor, McGill University
Website: https://www.mcgill.ca/geography/people/roulet



Publications
For a list of selected publications, please refer to: publication document


References
Cubasch, U and 40 others, 2001. Projections of future climate change. In: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, New York.
Frolking, S. et al., 2002. Modelling the seasonal to annual carbon balance of Mer Bleue Bog, Ontario, Canada. Global Biogeochemical Cycles, 16: 1029-1040.
Frolking, S. et al., 1998. Relationship between ecosystem productivity and photosynthetically active radiation for
northern peatlands. Global Biogeochemical Cycles, 12: 115-126.
Gorham, E., 1991. Northern peatlands: role in the carbon balance and probable responses to climatic warming.
Ecological Applications 1, 182-195.
Lafleur, P.M., Roulet, N.T., and Admiral, S., 2001. The annual cycle of CO2 exchange at a boreal bog peatland. J.
Geophys. Research, 106: 3071-3081.
Turunen, J.E., T.K. Tolonen and A. Reinikainen, 2002. Estimating carbon accumulation rates of undrained mires in
Finland – applications to boreal and subarctic regions. Holocene 12, 69-80.