Improving peat decomposition in a peatland greenhouse gas emissions model: Peatland-VU v3.

Accurate modelling of peatland carbon dynamics is critical for understanding their role in the global carbon cycle and predicting future greenhouse gas (GHG) fluxes. In this study, we present an updated version of the Peatland-VU model, Peatland-VU v3.0, designed to enhance the simulation of peat decomposition processes and below-ground soil organic matter (SOM) dynamics.A key focus of this development is the improved representation of SOM decomposition sensitivity to temperature, which we evaluate using both the Arrhenius equation and Q10 relationships. The model allows the specification of distinct Q10 values for eight different SOM pools and simulates decomposition in both anaerobic and aerobic soil layers. To capture seasonal and vegetation-specific dynamics, we also refined representations of harvest effects, leaf area index, phenology, and leaf senescence.We evaluate the model at two contrasting peatland sites in the Netherlands: the natural bog complex of the Weerribben and the drained peat pasture of Assendelft. These sites differ significantly in soil profiles, hydrology, and land-use history, offering insights into how these factors influence decomposition rates and net carbon dioxide and methane emissions.We highlight the benefits and limitations of the Q10 and Arrhenius approaches in modelling the temperature sensitivity of SOM decomposition, with implications for accurately representing peatland GHG fluxes under varying climatic and management scenarios. Additionally, we discuss potential model limitations, including missing processes that may be critical for simulating peatland responses to environmental change.This work provides new insights into peat decomposition dynamics and contributes to the development of more reliable tools for simulating peatland GHG emissions in both natural and managed ecosystems.