Freeze-thaw cycles simultaneously decrease peatland photosynthetic carbon uptake and ecosystem respiration

• Main Authors: Kuttim, Martin, Hofsommer, Maaike L., Robroek, Bjorn J. M., Signarbieux, Constant, Jassey, Vincent E. J., Laine, Anna M., Lamentowicz, Mariusz, Buttler, Alexandre, Ilomets, Mati, Mills, Robert T. E.
• Other Authors: Department of Forest Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: Finnish Environment Institute 2017
• Subjects: 1172 Environmental sciences; 4112 Forestry; MICROBIAL COMMUNITY STRUCTURE; ARCTIC TUNDRA SOILS; CLIMATE-CHANGE; CHLOROPHYLL FLUORESCENCE; SNOW COVER; CO2; TEMPERATURE; BOREAL; BOG; MANIPULATION; Arctic; Boreal Environment Research; Climate change; Tundra
• Online Access: http://hdl.handle.net/10138/208855

Decreasing snow cover in winter resulting from climate warming increases the incidence of freeze-thaw cycles (FTCs) in many ecosystems, including peatlands. As peatland ecosystems form a globally significant long-term carbon storage, understanding the effects of changing conditions in winter on carbon dynamics is essential. We studied how FTCs affect peatland carbon cycling by conducting mesocosm experiments with Sphagnum. Our results indicate an overall impeding effect of FTCs on Sphagnum photosynthesis, chlorophyll content, ecosystem respiration and enzymatic processes. A threefold reduction in photosynthesis in the FTC treatment was related to a decrease in chlorophyll content, showing that Sphagnum physiologically suffers from repeated FTCs. In the FTC treatment beta-glucosidase and phosphatase enzymatic activities decreased by 50% and 30%, respectively, whilst alanine remained unaffected, indicating that in peat soils short-term FTCs affect the carbon and phosphorus cycles, but not the nitrogen cycle. Long-term effects of FTCs deserve further studies. Peer reviewed