PEATLAND: A PROCES-BASED MODEL OF CARBON DIOXIDE AND METHANE FLUXES FROM PEAT SOILS

The management of peatlands has a large effect on the carbon balance of these areas. Since medieval times the coastal peat areas in the Netherlands have been drained for agriculture. However, plans exist to convert parts of these peatlands back into wetland nature reserves by raising water levels again. Since drainage began, the Dutch coastal peat areas became a source of CO₂. On the other hand, raising of the groundwater level may turn these areas in a source of CH₄, which is more effective as a greenhouse gas than CO₂.

PEATLAND is a process-based model of CO₂ and CH₄ emission from peat soils at various management scenarios. PEATLAND includes CO₂ and CH₄ production from different soil organic matter reservoirs, including the peat substrate of the soil. CO₂ production is modelled using first order decomposition rates. The decomposition constants are influenced by the environmental factors temperature, soil aeration, soil moisture and pH. The CH₄ emission includes production from fresh organic matter, methane oxidation in the soil, and transport by diffusion, through plant roots and bubbles. Both submodels are linked to a primary production model. The model is validated using closed chamber flux measurements at three sites in the Netherlands.

The model results indicate interesting links between CO₂ and CH₄ production in cases of a seasonally fluctuating water table. The CH₄ production during high water table periods is suppressed by aerobic decomposition of fresh organic matter reservoirs during low water table periods. In case of a winter-high, summer-low water table regime CH₄ flux peaks occur in spring and autumn. High CH₄ emission only occurs after a considerable raise of the water table. In some cases this may cause a net increase of the greenhouse gas flux (expressed in CO₂ equivalents) in spite of a decreased CO₂ flux.