Warming impacts on boreal fen CO2 exchange under wet and dry conditions

• Published in: Global Change Biology
• Main Authors: Laine, A.M., Mäkiranta, P., Laiho, R., Mehtätalo, L., Penttilä, T., Korrensalo, A., Minkkinen, K., Fritze, H., Tuittila, E-S
• Other Authors: Department of Forest Sciences, Kari Minkkinen / Principal Investigator, Forest Ecology and Management
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: 1172 Environmental sciences; 4112 Forestry; carbon dioxide; ecosystem respiration; gross photosynthesis; OTC; peatland; warming; water level drawdown; CLIMATE-CHANGE; GREENHOUSE-GAS FLUXES; PEATLANDS; WATER-TABLE MANIPULATION; TEMPERATURE RESPONSE; LEVEL DRAWDOWN; CARBON-DIOXIDE; METHANE FLUX; SUB-ARCTIC FEN; SOIL RESPIRATION; Arctic; Climate change
• Online Access: http://hdl.handle.net/10138/313134

Abstract Northern peatlands form a major soil carbon (C) stock. With climate change, peatland C mineralization is expected to increase, which in turn would accelerate climate change. A particularity of peatlands is the importance of soil aeration, which regulates peatland functioning and likely modulates the responses to warming climate. Our aim is to assess the impacts of warming on a southern boreal and a sub-arctic sedge fen carbon dioxide (CO2) exchange under two plausible water table regimes: wet and moderately dry. We focused this study on minerotrophic treeless sedge fens, as they are common peatland types at boreal and (sub)arctic areas, which are expected to face the highest rates of climate warming. In addition, fens are expected to respond to environmental changes faster than the nutrient poor bogs. Our study confirmed that CO2 exchange is more strongly affected by drying than warming. Experimental water level draw-down (WLD) significantly increased gross photosynthesis and ecosystem respiration. Warming alone had insignificant impacts on the CO2 exchange components, but when combined with WLD it further increased ecosystem respiration. In the southern fen, CO2 uptake decreased due to WLD, which was amplified by warming, while at northern fen it remained stable. As a conclusion, our results suggest that a very small difference in the WLD may be decisive, whether the C sink of a fen decreases, or whether the system is able to adapt within its regime and maintain its functions. Moreover, the water table has a role in determining how much the increased temperature impacts the CO2 exchange. This article is protected by copyright. All rights reserved. Peer reviewed