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Climate change predictions derived from coupled carbon-climate models are highly dependent on assumptions about feedbacks between the biosphere and atmosphere. One critical feedback occurs if C uptake by the biosphere increases in response to the fossil-fuel driven increase in atmospheric [CO(2)] ("CO(2) fertilization"), thereby slowing the rate of increase(More)
Increases in tree biomass may be an important sink for CO 2 as the atmospheric concentration continues to increase. Tree growth in temperate forests is often limited by the availability of soil nutrients. To assess whether soil nutrient limitation will constrain forest productivity under high atmospheric CO 2 , we studied the changes in forest litter(More)
Free-air CO2 enrichment (FACE) technology was used to expose a loblolly pine (Pinus taeda L.) forest to elevated atmospheric CO2 (ambient + 200 µl l-1). After 4 years, basal area of pine trees was 9.2% larger in elevated than in ambient CO2 plots. During the first 3 years the growth rate of pine was stimulated by ~26%. In the fourth year this stimulation(More)
Elevated concentrations of atmospheric CO2 increase plant biomass, net primary production (NPP) and plant demand for nitrogen (N). The demand for N set by rapid plant growth under elevated CO2 could be met by increasing soil N availability or by greater efficiency of N uptake. Alternatively, plants could increase their nitrogen-use efficiency (NUE), thereby(More)
The idea that the concentration of secondary metabolites in plant tissues is controlled by the availability of carbon and nitrogen in the environment has been termed the carbon±nutrient balance hypothesis (CNB). This hypothesis has been invoked both for prediction and for post hoc explanation of the results of hundreds of studies. Although it successfully(More)
Photosynthetic efficiency is often quantified as the light-limited, maximum quantum yield in ecophysiological studies. Four published comparative studies report that photosynthetic efficiency varies little among plant species of widely diverse origins, and that quantum yields were near the maximum theoretically attainable value. However, many other(More)
We compared radiation-use efficiency of growth (epsilon;), defined as rate of biomass accumulation per unit of absorbed photosynthetically active radiation, of forest plots exposed to ambient (approximately 360 micro l l-1) or elevated (approximately 560 micro l l-1) atmospheric CO2 concentration ([CO2]). Large plots (30-m diameter) in a loblolly pine(More)
Increased concentrations of CO 2 and ozone are predicted to lower nutritional quality of leaves for insect herbivores, which may increase herbivory as insects eat more to meet their nutritional demands. To test this prediction, we measured levels of herbivory in soybean grown in ambient air and air enriched with CO 2 or O 3 using free air gas concentration(More)
[1] In two parallel but independent experiments, Free Air CO 2 Enrichment (FACE) technology was used to expose plots within contrasting evergreen loblolly pine (Pinus taeda L.) and deciduous sweetgum (Liquidambar styraciflua L.) forests to the level of CO 2 anticipated in 2050. Net primary production (NPP) and net ecosystem production (NEP) increased in(More)