Proglacial wetlands: an overlooked CO2 sink within recently deglaciated landscapes

Abstract

Glacial retreat has uncovered vast landmasses in the European Alps over the last 150 years. Soil formation in these areas is likely slow due to low temperatures, lack of moisture, and short growing seasons. Previous studies have however focused solely on dry soils, omitting any water saturated locations. Our research shows that these water saturated locations are key locations of daytime CO2 uptake and have a significant role in carbon storage in the proglacial valley, despite their small surface area (<5 %). Loss-on-ignition analyses showed certain wetland soils contained up to 85 % carbon, suggesting these wetlands can become peatlands over time, storing large amounts of carbon. CO2 flux measurements showed atmospheric CO2 uptake in wetlands of all measured ages, even as young as 5 years after deglaciation. As little moss or plant cover was generally observed at locations < 50 years, the autotrophic microbial community likely plays an important role in these young systems. Non-saturated locations showed a much larger variation in daytime CO2 fluxes, with both emission and uptake of CO2 being observed across ages. Overall, our research shows that wetlands are hotspots of biological activity and pedogenic processes in proglacial areas and should therefore receive more attention in proglacial research.