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The Effects of Elevated CO2 on Leaf Dark Respiration Rates in Two Forest Species
Hamilton, J.G., Thomas, R.B. and DeLucia, E.H.  2001.  Direct and indirect effects of elevated CO2 on leaf respiration in a forest ecosystem.  Plant, Cell and Environment 24: 975-982.

What was done
Circular FACE plots (30 meters in diameter) receiving nocturnal atmospheric CO2 concentrations of 400 and 600 ppm were established several years ago (1996) in a now 17-year-old loblolly pine (Pinus taeda L.) plantation in North Carolina, USA.  This evergreen plantation also contains several hardwood species, including the economically important deciduous sweetgum (Liquidambar styraciflua L.) tree.  In this paper, the authors report the effects of elevated CO2 on leaf dark respiration rates in these two forest species.

What was learned
Elevated CO2 reduced rates of leaf dark respiration in the deciduous sweetgum trees by an average of 10% but did not significantly affect leaf dark respiration rates in the coniferous loblolly pines.

What it means
Because elevated CO2 has been shown to have concurrently increased leaf photosynthetic rates in both of these forest species (DeLucia and Thomas, 2000; DeLucia et al., 1999), both species would be expected to have experienced concomitant CO2-induced increases in biomass production and net carbon accumulation, as has indeed been documented to be true (Naidu and DeLucia 1999).  Hence, as the air's CO2 content continues to rise, forests comprised of these two species of trees should exhibit increasingly greater rates of growth and carbon sequestration.

DeLucia, E.H., Hamilton, J.G., Naidu, S.L., Thomas, R.B., Andrews, J.A., Finzi, A., Lavine, M., Matamala, R., Mohan, J.E., Hendrey, G.R. and Schlesinger, W.H.  1999.  Net primary production of a forest ecosystem with experimental CO2 enrichment.  Science 284: 1177-1179.

DeLucia, E.H. and Thomas, R.B.  2000.  Photosynthetic responses to CO2 enrichment of four hardwood species in a forest understory.  Oecologia 122: 11-19.

Naidu, S.L. and DeLucia, E.H.  1999.  First-year growth response of trees in an intact forest exposed to elevated CO2Global Change Biology 5: 609-613.