GHG Emissions from a Mountain Peatland Under a Changing Climate — a Microcosm Study.

Globally, boreal and subarctic peatlands store about 30% of soil C and account for up to 5% of CH₄ emissions. Western Canadian peatlands constitute about 0.25% of the global land area and store 2.1% of global soil C. However, the feedback of peatland C cycling to global warming is still uncertain, especially for subsurface peat. In peatlands of the northern Rocky Mountains, peat may be underlain by older peat or by mineral sediments, which vary in terms of properties and C&N cycling. This suggests that the interaction of peat and mineral layers may make the feedback of greenhouse gas (GHG) emissions to global warming more complex. Therefore, our objective is to study the effect of subsurface peat and mineral layers on GHG emissions and how peat GHG might respond in a changing climate.

Two soil profiles – sedge peat underlain by mineral/calcareous sediments (PMC) and sedge peat underlain by moss peat (PP) – were incubated for 28 days under four treatments: current temperature/current water table, higher temperature/current water table, current temperature/lower water table, higher temperature/lower water table. Surface GHG emissions and GHG concentration from different depths (surface, above water table, below water table and above mineral contact) were monitored. Results indicated that temperature and soil profile classes were the main factors regulating GHG – at surface and at depth – in most samples. There was no interaction effect of soil profile class and temperature for GHG emissions from the surface.  There was, however, an interaction effect in the subsurface, with PP profiles exhibiting greater N₂O concentration at all depths except below water table and greater CH₄ concentration in samples from above water table with increased temperature. This study highlights potential sources of variability for GHG emissions from mountain peatlands in changing climate and the importance of characterizing subsurface properties in complex peatland environments.