Cumulative response of ecosystem carbon and nitrogen stocks to chronic CO2 exposure in a subtropical oak woodland. Issue 3 (30th May 2013)

• Record Type: Journal Article
• Authors: Hungate, Bruce A.; Dijkstra, Paul; Wu, Zhuoting; Duval, Benjamin D.; Day, Frank P.; Johnson, Dale W.; Megonigal, J. Patrick; Brown, Alisha L. P.; Garland, Jay L.
• Is Part Of: New phytologist. Volume 200:Issue 3(2013)
• Page Start: 753
• Page End: 766
• Publication Date: 2013-05-30
• Subjects: Botany -- Periodicals; 580
• DOI: 10.1111/nph.12333
• Languages: English
• ISSNs: 0028-646X

Abstract

<abstract abstract-type="main" id="nph12333-abs-0001"> <title>Summary</title> <p> <list id="nph12333-list-0001" list-type="bullet"> <list-item> <p>Rising atmospheric carbon dioxide (CO<sub>2</sub>) could alter the carbon (C) and nitrogen (N) content of ecosystems, yet the magnitude of these effects are not well known. We examined C and N budgets of a subtropical woodland after 11 yr of exposure to elevated CO<sub>2</sub>.</p> </list-item> <list-item> <p>We used open‐top chambers to manipulate CO<sub>2</sub> during regrowth after fire, and measured C, N and tracer <sup>15</sup>N in ecosystem components throughout the experiment.</p> </list-item> <list-item> <p>Elevated CO<sub>2</sub> increased plant C and tended to increase plant N but did not significantly increase whole‐system C or N. Elevated CO<sub>2</sub> increased soil microbial activity and labile soil C, but more slowly cycling soil C pools tended to decline. Recovery of a long‐term <sup>15</sup>N tracer indicated that CO<sub>2</sub> exposure increased N losses and altered N distribution, with no effect on N inputs.</p> </list-item> <list-item> <p>Increased plant C accrual was accompanied by higher soil microbial activity and increased C losses from soil, yielding no statistically detectable effect of elevated CO<sub>2</sub> on net ecosystem C uptake. These findings challenge the treatment of terrestrial ecosystems responses to elevated CO<sub>2</sub> in current biogeochemical models, where the effect of elevated CO<sub>2</sub> on ecosystem C balance is described as enhanced photosynthesis and plant growth with decomposition as a first‐order response.</p> </list-item> </list> </p> </abstract>