What was done
The authors developed a model for calculating net ecosystem exchange (NEE) of CO2 between wetland sedge (Scirpus olneyi Gray) communities and the atmosphere that is based on published ecophysiological data and additional measurements of photosynthetic parameters at the site of the long-term Chesapeake Bay CO2-enrichment (to 350 ppm above ambient) study described by Curtis et al. (1989a,b).

What was learned
The S. olneyi community responded favorably to the near-doubled atmospheric CO2 concentration by increasing its NEE by 35-40%.  The authors say this result is to be compared with a mean net photosynthesis increase of 74% reported by Gielen and Ceulemans (2001) in a review of 28 experiments on poplar trees and a mean increase of 60% reported by Norby et al. (1999) in a more extensive review that included several tree species and ecosystems.

What it means
The authors say that "because Scirpus-dominated ecosystems are extremely productive (Drake and Leadley, 1991), a 35-40% productivity increase might represent a larger additional amount of carbon fixed as compared to a 60% increase in less productive forest ecosystems."   Hence, because wetlands cover approximately six million square kilometers of land worldwide, with about 15% of that area located in temperate regions (Mitsch et al., 1994), they conclude that "temperate C3 wetlands have a huge potential for increased plant productivity [and, therefore, sequestration of carbon] during the 21st century."

References
Curtis, P.S., Drake, B.G., Leadly, P.W., Arp, W.J. and Whigham, D.F.  1989a.  Growth and senescence in plant communities exposed to elevated CO2 concentrations on an estuarine marsh.  Oecologia 78: 20-26.

Curtis, P.S., Drake, B.G. and Whigham, D.F.  1989b.  Nitrogen and carbon dynamics in C3 and C4 estuarine marsh plants grown under elevated CO2 in situ.  Oecologia 78: 297-301.

Drake, B.G. and Leadley, P.W.  1991.  Canopy photosynthesis of crops and native plant communities exposed to long-term elevated CO2.  Plant, Cell and Environment 14: 853-860.

Gielen, B. and Ceulemans, R.  2001.  The likely impact of rising atmospheric CO2 on natural and managed Populus: a literature review.  Environmental Pollution 115: 335-358.

Mitsch, W.J., Mitsch, R.H. and Turner, R.E.  1994.  Wetlands of the Old and New Worlds: ecology and management.  In: Mitsch, W.J., Ed., Global Wetlands Old World and New, Elsevier, Amsterdam, the Netherlands.

Norby, R.J., Wullschleger, S.D., Gunderson, C.A., Johnson, D.W. and Ceulemans, R.  1999.  Tree responses to rising CO2 in field experiments: implications for the future forest.  Plant, Cell and Environment 22: 683-714.