Modelling CO2 and CH4 fluxes from drained and natural peatlands with the PEATLAND-VU model

Draining peatlands results in oxic soil conditions that causes microbial oxidation of peat. Drained peatlands are a large source for CO₂ emissions, contributing 2-5% to the total anthropogenic greenhouse gas emissions. Understanding processes that contribute to peat oxidation are useful to simulate, predict and project CO₂ emission in different environmental conditions. In wet conditions, soil is anoxic, which leads to an increase in methane (CH₄) emission. Wetlands, including peatlands, are the largest natural source of CH₄. Weather conditions, water table height, substrate availability, and vegetation type play a crucial role in the amount of CH₄ that is emitted. The dynamic of CH₄ production and oxidation, driven by the above mentioned factors, is complex. Nevertheless, for both CO₂ and CH₄, it is essential to be able to simulate these fluxes with a mechanistical model for monitoring and predicting greenhouse gas emission from peatlands.

PEATLAND-VU is a 1D process based model, consisting of four submodels for 1) soil physics (water table, soil temperature and soil moisture), 2) biomass production, 3) CH₄ production, oxidation and transport (diffusion, ebullition and plant transport), and 4) CO₂ production. Here, CO₂ production is represented as the sum of decomposition from different soil organic matter (SOM) pools, like litter, root exudates, microbial biomass, and peat.

We calibrated the PEATLAND-VU model for two intensively used drained peat meadows and a wet Sphagnum-reed peatland in the Netherlands. These sites have 2-4 years of CO₂ flux and CH₄ flux (Sphagnum-reed peatland only) data. In our presentation we will show that the model performed well for simulating CO₂ and CH₄ fluxes. We will focus on the contribution of peat oxidation to the total CO₂ emission, and show results of different water table management and future climate scenarios. Furthermore, for the Sphagnum-reed peatland the modelled CH₄ production, CH₄ oxidation, and the transport pathways resulting in the net CH₄ flux will be discussed.