Variability in exchange of CO₂ across 12 northern peatland and tundra sites

• Published in: Global change biology Vol. 16; no. 9; pp. 2436 - 2448
• Main Authors: LUND, MAGNUS, LAFLEUR, PETER M, ROULET, NIGEL T, LINDROTH, ANDERS, CHRISTENSEN, TORBEN R, AURELA, MIKA, CHOJNICKI, BOGDAN H, FLANAGAN, LAWRENCE B, HUMPHREYS, ELYN R, LAURILA, TUOMAS, OECHEL, WALTER C, OLEJNIK, JANUSZ, RINNE, JANNE, SCHUBERT, PER, NILSSON, MATS B
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.09.2010; Blackwell Publishing Ltd
• Subjects: Air temperature; Aquatic ecosystems; biomass; carbon; Carbon dioxide; Climate change; data collection; Earth and Related Environmental Sciences; Ecology; ecosystem respiration; Ecosystem structure; ecosystems; eddy covariance; environmental factors; Environmental Sciences related to Agriculture and Land-use; Europe; Geovetenskap och miljövetenskap; Geovetenskap och relaterad miljövetenskap; Global warming; Growing season; heat sums; leaf area index; Leaves; Measurement techniques; Miljö- och naturvårdsvetenskap; mire; Natural Sciences; Naturgeografi; Naturvetenskap; net ecosystem exchange; normalized difference vegetation index; North America; Nutritional status; Organic carbon; peatland; Peatlands; photosynthesis; Physical Geography; Primary production; primary productivity; Respiration; soil; summer; Taiga & tundra; Tundra; Vapor pressure; Vegetation; wetland; Wetlands; Arctic; North America; PN, Arctic; Europe
• ISSN: 1354-1013; 1365-2486; 1365-2486
• DOI: 10.1111/j.1365-2486.2009.02104.x

Many wetland ecosystems such as peatlands and wet tundra hold large amounts of organic carbon (C) in their soils, and are thus important in the terrestrial C cycle. We have synthesized data on the carbon dioxide (CO₂) exchange obtained from eddy covariance measurements from 12 wetland sites, covering 1-7 years at each site, across Europe and North America, ranging from ombrotrophic and minerotrophic peatlands to wet tundra ecosystems, spanning temperate to arctic climate zones. The average summertime net ecosystem exchange of CO₂ (NEE) was highly variable between sites. However, all sites with complete annual datasets, seven in total, acted as annual net sinks for atmospheric CO₂. To evaluate the influence of gross primary production (GPP) and ecosystem respiration (Reco) on NEE, we first removed the artificial correlation emanating from the method of partitioning NEE into GPP and Reco. After this correction neither Reco (P= 0.162) nor GPP (P= 0.110) correlated significantly with NEE on an annual basis. Spatial variation in annual and summertime Reco was associated with growing season period, air temperature, growing degree days, normalized difference vegetation index and vapour pressure deficit. GPP showed weaker correlations with environmental variables as compared with Reco, the exception being leaf area index (LAI), which correlated with both GPP and NEE, but not with Reco. Length of growing season period was found to be the most important variable describing the spatial variation in summertime GPP and Reco; global warming will thus cause these components to increase. Annual GPP and NEE correlated significantly with LAI and pH, thus, in order to predict wetland C exchange, differences in ecosystem structure such as leaf area and biomass as well as nutritional status must be taken into account.