PVN 1.0: using dynamic PFTs and restoration scenarios to model CO2 and CH4 emissions in peatlands

Peatlands are the world’s largest terrestrial carbon store. Despite covering only 3% of the planet’s land surface, peatlands store 30% of the planet’s terrestrially available carbon. The Dutch government’s 2019 National Climate Agreement committed to reduce the contribution of peatlands to total national Dutch GHG emissions, by 1 MtonCO 2 per year (or 20%) until 2030. Countries with similarly degraded peatlands are likely to face similar commitments in the coming years. Restoration (or rewetting) is a proposed solution to reduce land subsidence and increase carbon sequestration in agricultural peatlands but 5 is often accompanied by large CH 4 emissions. Whilst, previous studies have investigated whether singular plant types impact the greenhouse gas (GHG) emissions of peatlands, few (or no) studies have investigated the impact of plant composition on GHG emissions in peatlands. To assess the impact of dynamic vegetation on subsequent GHG ﬂuxes in peatlands, we developed a new model, Peatland-VU-NUCOM (PVN). This is the second process-based model to date, capable of simulating dynamic vegetation, CO 2 , and CH 4 emissions 10 in peatlands. The new PVN model simulates CH 4 and CO 2 ﬂuxes in relation to the plant community composition. The PVN model includes plant competition, CH 4 diffusion, ebullition, root, shoot, litter exudate production, belowground decomposition, and aboveground moss development, under changing water table and climatic conditions. The model was compared against observational data collected at two sites in the Netherlands. These results showed that plant communities impact net GHG emissions. This is the ﬁrst time that a peatland emissions model is able to investigate the role of re-introducing peat forming vegetation on subsequent GHG emissions. We also found that the initial plant community inﬂuenced the potential for harvest events to reduce GHG emissions. These results indicated that plant community restoration is a critical component of peatland restoration. activities that do not consider vegetation restoration. The second pathway, rewetting followed by re-establishment, refers to rewetting activities that re-establish, or re-introduce, peat forming vegetation. We hypothesise that plant composition inﬂuences 90 the GHG emissions subsequent rewetting. Automated ﬂux-chamber measurements taken at two peatland sites, one ’abandoned’ and one ’re-established’ site, in the Netherlands are used to evaluate the model. The new PVN model simulates CH 4 and CO 2 ﬂuxes in relation to the plant community composition, including the belowground and decomposition of plant detritus under changing water table and climatic conditions. urgent need to reduce land subsidence whilst achieving carbon sequestration in peatlands. These results showed that peatland restoration efforts that rewet without restoring peat-forming vegetation will likely result in larger GHG emissions than restoration efforts that rewet and abandon. These results indicate that vegetation 760 re-establishment is a critical component of peatland restoration. Author contributions. TL, KvH, and MH developed the theoretical framework of the model. TL performed the model developments, composed the PFTs, made the ﬁgures, all analyses, and wrote the paper. TL and KvH collected the observational data, and developed the model parameterisation scheme, and soil proﬁles. KvH pre-processed the observational data and offered valuable suggestions on the development and calibration of the model. HD participated in the writing of this paper. HD, MH, KvH,YvdV participated in the revision of this paper. DH, HD, MH, and KvH aquired the funding and