·Rising atmospheric carbon dioxide (CO2) 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 CO2.
·We used open-top chambers to manipulate CO2 during regrowth after fire, and measured C, N and tracer 15N in ecosystem components throughout the experiment.
·Elevated CO2 increased plant C and tended to increase plant N but did not significantly increase whole-system C or N. Elevated CO2 increased soil microbial activity and labile soil C, but more slowly cycling soil C pools tended to decline. Recovery of a long-term 15N tracer indicated that CO2 exposure increased N losses and altered N distribution, with no effect on N inputs.
· Increased plant C accrual was accompanied by higher soil microbial activity and increased C losses from soil, yielding no statistically detectable effect of elevated CO2 on net ecosystem C uptake. These findings challenge the treatment of terrestrial ecosystems responses to elevated CO2 in current biogeochemical models, where the effect of elevated CO2 on ecosystem C balance is described as enhanced photosynthesis and plant growth with decomposition as a first-order response.
Original Publication Citation
Hungate, B. A., Dijkstra, P., Wu, Z. T., Duval, B. D., Day, F. P., Johnson, D. W., . . . Garland, J. L. (2013). Cumulative response of ecosystem carbon and nitrogen stocks to chronic CO2 exposure in a subtropical oak woodland. New Phytologist, 200(3), 753-766. doi:10.1111/nph.12333
Hungate, Bruce A.; Dijkstra, Paul; Wu, Zhuoting; Duval, Benjamin D.; Day, Frank P.; and Brown, Alisha L.P., "Cumulative Response of Ecosystem Carbon and Nitrogen Stocks to Chronic CO2 Exposure in a Subtropical Oak Woodland" (2013). Biological Sciences Faculty Publications. 247.