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Fine-Root Respiration in a Loblolly Pine and Sweetgum Forest Growing in Elevated CO2

K. George, R. J. Norby, J. G. Hamilton and E. H. DeLucia
The New Phytologist
Vol. 160, No. 3 (Dec., 2003), pp. 511-522
Published by: Wiley on behalf of the New Phytologist Trust
Stable URL: http://www.jstor.org/stable/1514306
Page Count: 12
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Fine-Root Respiration in a Loblolly Pine and Sweetgum Forest Growing in Elevated  CO2
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Abstract

• The loss of carbon below-ground through respiration of fine roots may be modified by global change. Here we tested the hypothesis that a reduction in N concentration of tree fine-roots grown in an elevated atmospheric CO2 concentration would reduce maintenance respiration and that more energy would be used for root growth and N uptake. We partitioned total fine-root respiration (R T) between maintenance (R M), growth (R G), and N uptake respiration (R N) for loblolly pine (Pinus taeda) and sweetgum (Liquidambar styraciflua) forests exposed to elevated CO2. • A substantial increase in fine-root production contributed to a 151% increase in R G for loblolly pine in elevated CO2. Root specific R M for pine was 24% lower under elevated CO2 but when extrapolated to the entire forest, no treatment effect could be detected. • $R_{{\rm G}}(<10\%)$ and $R_{{\rm N}}(<3\%)$ were small components of R M in both forests. Maintenance respiration was the vast majority of R T, and contributed 92% and 86% of these totals at the pine and sweetgum forests, respectively. • The hypothesis was rejected because the majority of fine-root respiration was used for maintenance and was not reduced by changes in root N concentration in elevated CO2. Because of its large contribution to R T and total soil CO2 efflux, changes in R M caused by warming may greatly alter carbon losses from forests to the atmosphere.

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