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 yrs. Soil formation in these areas is considered to be 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 CO₂ uptake and have a significant role in carbon storage in the proglacial valley, despite their small surface area. 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 yrs, the autotrophic microbial community likely plays an important role in these young systems. Non-saturated locations showed a much larger variation in 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.