Metla Project 7114
Modelling and extrapolation of peatland greenhouse gas fluxes
Keywords: CH4, CO2, N2O, greenhouse gases, peat, peatland ecosystem
Research project group: Distinct projects 1 - Structure and function of forest ecosystems
Objectives The principal aim of this project is to combine statistical, site type specific gas exchange data and physically based ecosystem models with weather parameters, into dynamical (weather dependent) annual emission factors for the atmospheric exchange of CO2, CH4 and N2O. A regional assessment of gas balances will be attempted. To achieve this, gas exchange data from the model land use sites and corresponding high resolution time series of weather data and nationwide distribution of peatlands under various land use must be obtained. Gas exchange in natural peatlands is considered as a baseline, against which impacts from other land use schemes are evaluated.
A weather dependent peat soil model will ultimately form a framework for estimating the gas fluxes under varying measured or simulated weather patterns. This approach of obtaining GHG fluxes will be employed to estimate “dynamic emission factors” from the different land use forms. The basis for such estimation will be the data obtained in field from the model sites in this programme, or measured earlier using comparable techniques. It is thus essential that the data collected by the different projects will be processed into regression based reconstruction functions in a consistent manner. To achieve this, the modelling project will interact with all the measurement projects.
The dynamical, time and weather dependent emission factors and improved regional information on peatland use in Finland will be utilized in regional emission estimates. A user interface will be planned for future calculations, data visualization and presentation. The functions will be made available for a life-cycle analysis of the use of peat and peatlands in Finland.
Results The first year of the project has been used for testing several existing process models on C cycling and GHG emissions in pristine peatlands. Field data collected from Salmisuo, eastern Finland, and Kaamanen in Finnish Lapland have been used as reference for PCARS (Frolking et al. 2002). The comparison of modelled and measured data shows that a reasonable agreement in gross photosynthesis and respiration can be reached using PCARS. Thus a useful estimate of net CO2 exchange is obtained. However, dynamics of methane were not satisfactorily reproduced by PCARS. Hence, we plan to employ a process oriented model developed for Finnish conditions by Kettunen(2003).
We have made preparations to run two other models, DNDC (Zhang et al., 2002) and a peat soil climate model by Granberg et al. (1999). The latter model is presently being implemented as a computer software, adapted for our purposes. For the purpose, collaboration with the Department of Computer Science at the University of Joensuu has been established.
The models available at the moment require water table as input. Therefore, we plan to test and further develop a Finnish model PeatSoil, formulated earlier in collaboration with the Universities of Joensuu and Helsinki (Weiss et al. 1998, Shurpali et al. 2003). A physically based model on peat moisture and temperature is essential in order to connect local weather time series with soil oxic/anoxic conditions, and processes of primary production and decomposition into gaseous fluxes of CO2, CH4 and N2O. Our primary concern now is to have access to, or to develop a sound soil model that would be useful for peatlands. There is a need for further measurements of soil physical parameters, especially concerning the ecohydrology of undrained peatlands.
Frolking, S., Roulet, N.T., Moore, T.R., Lafleur, P.M., Bubier, J.L. and Crill, P.M. 2002. Modelling seasonal to annual carbon balance of Mer Bleue Bog, Ontario, Canada. Global Biogeochemical Cycles, VOL. 16, NO. 3, 10.1029/2001GB001457, 2002
Granberg, G., Grip, H., Lofvenius, M.O., Sundh, I., Svensson, B.H., and Nilsson, M. A simple model for simulation of water content, soil frost, and soil temperatures in boreal mixed mires. Water Resources Research, 35(12): 3771-3782, 1999.
Kettunen, A. Connecting methane fluxes to vegetation cover and water table fluctuations at microsite level: A modeling study. (accepted to Global Biogeochemical Cycles), 2003.
Shurpali, N.J., Weiss, R., and Alm, J. Constraints to simulating water table and temperature of pristine peat soils of Finland. In: Järvet, A. & Lode, E. (eds.). Ecohydrological Processes in Northern Wetlands. Selected papers of International Conference & Educational Workshop, Tallinn, Estonia 30 June - 4 July 2003. Tallinn - Tartu. p. 245-249, 2003.
Weiss, R. Alm, J. Laiho, R. and Laine, J. Modeling moisture retention in peat soils. Soil sci.Soc.Am.J 62: 305-313, 1998.
The Finnish Forest Research Institute,
PL 68, FI-80101 JOENSUU, FINLAND
Phone: +358 29 532 3107
Heinonen, Jaakko, JO (2005), Juutinen, Sari (2004), Shurpali, Narasinha (2002-05)
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