Carbon and energy fluxes from a spatially heterogeneous permafrost peatland
Silvie R Harder1, Nigel T Roulet
2, Ian B Strachan
3, Patrick M Crill
4 and Luc Pelletier
1, (1)McGill University, Montreal, QC, Canada, (2)McGill University, Department of Geography, Montreal, QC, Canada, (3)McGill University, Department of Natural Resource Sciences, Montreal, QC, Canada, (4)Stockholm University, Dept. of Geological Sciences and Bolin Centre for Climate Research, Stockholm, Sweden
Contact First Author: Silvie R Harder; silvie.harder@mail.mcgill.ca
English Abstract:
Various microforms, created by spatially differential thawing of permafrost, make up the subarctic heterogeneous Stordalen peatland (68°22’N, 19°03’E), near Abisko, Sweden. This results in significantly different peatland vegetation communities across short distances, as well as differences in wetness, peat temperatures, snow distribution and therefore carbon and energy fluxes. In recent decades, the permafrost extent of Stordalen has been markedly shrinking with warming air temperatures as well as differential snow distribution. When snow accumulates along the margins of the permafrost peat plateaus and palsas, the increased insulation maintains warmer ground temperatures as compared to the tops of the peat plateaus and palsas where the snow is blown clear. This insulation can advance permafrost thaw, leading to changes in vegetation communities and local hydrology as well as impacts to both the energy and carbon balances at this peatland.
Since 2012, we have been measuring the spatially integrated CO2, energy and water vapour fluxes from this peatland complex using eddy covariance (EC). We have also been examining the CO2 exchange from specific plant communities within the EC tower footprint (autochambers). LIDAR was used to produce a 1 m resolution digital evaluation model of the complex and the spatial distribution of plant functional types (PFTs) across the peatland was obtained from concurrent high-resolution digital colour air photography trained from vegetation surveys. The EC footprint is calculated for every half-hour and PFT based models are run with the corresponding environmental variables. These models calculate light use efficiency as well as ecosystem respiration for the different PFTs.
Our results show that the Sphagnum, palsa, and sedge PFTs have distinctly different light use efficiency models, and that the tower fluxes are dominated by a blend of the Sphagnum and palsa PFTs. We also see a distinctly different energy partitioning between the fetches containing intact permafrost and those where the permafrost has thawed: the evaporative efficiency is higher and the Bowen ration lower for the thawed fetches.
