Peatland CO2, CH4 and WT under climate change: process-based simulations of alternative land-uses

Peatland greenhouse gas dynamics are affected by anthropogenic land-use but also climate change, and especially methane emissions are expected to increase due to warmer temperatures. We study peatland sites in Europe using process-based JSBACH-HIMMELI ecosystem model, which includes the peat-YASSO soil carbon model and HIMMELI methane production and transport model. The model is capable of simulating peatlands and peatlands drained for forestry with a separate forestry-growth model. We account for drainage by modifying the water table level. 

Here we use CMIP 5 and CMIP 6 climate scenarios including IPSL, MPI and CNRM climate models and RCP 2.6, 4.5 and 8.5 pathways. We first simulate the peatland sites with their current land-use and set the model parameters according to in-situ measurements of GHGs and hydrology when available or otherwise use Sentinel 2 -based estimation and default set of parameters. 

We also simulate different land use options for historical period the site being either pristine, drained for forestry, or drained for agriculture or peat extraction. For future scenarios, we simulate the site being pristine or restored by rewetting or afforestation. We study the temporal dynamics of soil carbon, water table level, carbon dioxide and methane fluxes due to changes in management and in alternative management scenarios. We also study the trends climate change possesses and how increasing drought events affect the peatlands. 

Our results showed that the peatlands became more climate-warming in Radiative Forcing due to increased methane emissions, while the effect solely on water table level or Net Ecosystem Exchange was small. Drought events became more important on their contribution to annual GHG budget, but the intensity of emissions during droughts did not change notably. Peatland rewetting showed the return of carbon sink, and the methane emissions increased for a couple of decades depending on the water table level.