Releases of the greenhouse gases carbon dioxide (CO2) and methane (CH4) from thawing permafrost are expected to be among the largest feedbacks to climate from arctic ecosystems. However, the current net carbon (C) balance of terrestrial arctic ecosystems is unknown. Recent studies suggest that these ecosystems are sources, sinks, or approximately in balance at present…. More

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It is necessary to partition eddy covariance measurements of carbon dioxide exchange into its offsetting gross fluxes, canopy photosynthesis, and ecosystem respiration, to understand the biophysical controls on the net fluxes. And independent estimates of canopy photosynthesis (G) and ecosystem respiration (R) are needed to validate and parametrize carbon cycle models that are coupled with… More

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The effect of elevated atmospheric CO2 concentration (Ca) on the aboveground biomass of three oak species, Quercus myrtifolia, Q. geminata, and Q. chapmanii, was estimated nondestructively using allometric relationships between stem diameter and aboveground biomass after four years of experimental treatment in a naturally fire-regenerated scrub-oak ecosystem. After burning a stand of scrub-oak vegetation, re-growing… More

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For two species of oak, we determined whether increasing atmospheric CO2 concentration (Ca) would decrease leaf mitochondrial respiration (R) directly, or indirectly owing to their growth in elevated Ca, or both. In particular, we tested whether acclimatory decreases in leaf-Rubisco content in elevated Cawould decrease R associated with its maintenance. This hypothesis was tested in… More

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Elevated atmospheric carbon dioxide (Ca) usually reduces stomatal conductance, but the effects on plant transpiration in the field are not well understood. Using constant-power sap flow gauges, we measured transpiration from Quercus myrtifolia Willd., the dominant species of the Florida scrub-oak ecosystem, which had been exposed in situ to elevated Ca (350 µmol mol−1 above ambient) in… More

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We report the results of a 2-year study of effects of the elevated (current ambient plus 350 μmol CO2 mol−1) atmospheric CO2 concentration (Ca) on net ecosystem CO2 exchange (NEE) of a scrub–oak ecosystem. The measurements were made in open-top chambers (OTCs) modified to function as open gas-exchange systems. The OTCs enclosed samples of the ecosystem (ca…. More

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The long-term effects of elevated (ambient plus 350 μmol mol−1) atmospheric CO2 concentration (Ca) on the leaf senescence of Quercus myrtifolia Willd was studied in a scrub-oak community during the transition from autumn (December 1997) to spring (April 1998). Plants were grown in large open-top chambers at the Smithsonian CO2 Research Site, Merritt Island Wildlife Refuge,… More

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