Effect of post-thaw hydrological changes during the degradation process of a palsa

• Main Authors: Laurent, Melissa, Hoffman, Mathias, Strauss, Jens, Schaller, Joerg, Verdonen, Marianna, Kumpula, Timo, Baysinger, Mackenzie, Treat, Claire
• Format: Conference Object
• Language: unknown
• Published: 2023
• Subjects: palsa; permafrost
• Online Access: https://epic.awi.de/id/eprint/58584/; https://epic.awi.de/id/eprint/58584/1/Laurent_EUCOP2023-ABSTRACTS-11.pdf; https://hdl.handle.net/10013/epic.b936de79-a70b-4d77-bd94-4cead4dc49ac

With climate change, discontinuous permafrost is thawing rapidly and is predicted to reach a “tipping point” in the next decade. Permafrost affected peatlands store about 185±66 Pg C. Due to permafrost thaw, the landscape topographies and hydrologic conditions could change quickly and thus, release carbon (C) stored in soils. However, there is a current lack of understanding regarding the C lability after post- thaw and how the microbial community and labile C in the water will affect methane (CH4) and carbon dioxide (CO2) fluxes. Here, we quantified and qualified the effect of hydrologic changes on CH4 and CO2 emissions and production during the thawing process of a palsa (peaty permafrost mounts, mainly in discontinuous permafrost areas). We did a chronosequence study by measuring CH4 and CO2 emissions along a thawing transect from an intact palsa to a thawed wetland site during fall. Additionally, we mimicked a palsa degradation by incubating 1 m soil cores from the palsa and the wetland sites. We inoculated the incubation with water from the thawed site to study the effect of hydrological changes after permafrost thaw. The CO2 and CH4 emissions were continuously measured for 60 days. Additionally, dissolved gas, as well as nutrients were sampling over the entirety of the incubation time. The preliminary results from the field measurements showed that the intact palsa and the intermediate site behaved as a net C sink whereas, the thawed wetland site had the highest CH4 emissions (20 – 40 ppm). Furthermore, we showed that this mesocosm-scale incubation setup is an efficient and robust way to study C cycle dynamics and more accurately upscale laboratory results to the field. With permafrost thaw and former areas turning into wetlands more greenhouse gases will be emitted. Therefore, bridging scale is necessary to better estimate the future C emissions.