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Effects of Elevated Atmospheric CO2 on Water Relations in a Scrub-Oak Community
Hungate, B.A., Reichstein, M., Dijkstra, P., Johnson, D., Hymus, G., Tenhunen, J.D., Hinkle, C.R. and Drake, B.G.  2002.  Evapotranspiration and soil water content in a scrub-oak woodland under carbon dioxide enrichment.  Global Change Biology 8: 289-298.

What was done
The authors measured daily rates of evapotranspiration and soil moisture in mature scrub-oak communities growing within open-top chambers receiving atmospheric CO2 concentrations of 380 and 700 ppm over an eight-month period to study the effects of elevated CO2 on water-use in these woody communities.

What was learned
Elevated CO2 significantly reduced the mean daily rate of evapotranspiration by 19% throughout the eight-month study, in spite of 20-40% increases in leaf area index within the CO2-enriched chambers.  In addition, elevated CO2 significantly increased the soil moisture content in the 3- to 10-cm soil depth interval.

What it means
As the CO2 content of the air continues to rise, scrub-oak communities - and possibly other woody-species-dominated ecosystems - will likely experience reductions in evapotranspiration.  Consequently, such ecosystems should exhibit greater soil moisture contents, which should enable their various component species to better withstand periods of reduced rainfall.

Reviewed 5 June 2002