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Exposure to an enriched CO 2 atmosphere alters carbon assimilation and allocation in a pine forest ecosystem
Schäfer, Karina V. R.; Oren, Ram; Ellsworth, David S.; Lai, Chun-Ta; Herrick, Jeffrey D.; Finzi, Adrien C.; Richter, Daniel D.; Katul, Gabriel G.
Schäfer, Karina V. R.; Oren, Ram; Ellsworth, David S.; Lai, Chun-Ta; Herrick, Jeffrey D.; Finzi, Adrien C.; Richter, Daniel D.; Katul, Gabriel G.
2003-10
Citation:SchÄfer, Karina V . R.; Oren, Ram; Ellsworth, David S.; Lai, Chun-Ta; Herrick, Jeffrey D.; Finzi, Adrien C.; Richter, Daniel D.; Katul, Gabriel G. (2003). "Exposure to an enriched CO 2 atmosphere alters carbon assimilation and allocation in a pine forest ecosystem." Global Change Biology 9(10): 1378-1400. <http://hdl.handle.net/2027.42/73982>
Abstract: We linked a leaf-level CO 2 assimilation model with a model that accounts for light attenuation in the canopy and measurements of sap-flux-based canopy conductance into a new canopy conductance-constrained carbon assimilation (4C-A) model. We estimated canopy CO 2 uptake ( A nC ) at the Duke Forest free-air CO 2 enrichment (FACE) study. Rates of A nC estimated from the 4C-A model agreed well with leaf gas exchange measurements ( A net ) in both CO 2 treatments. Under ambient conditions, monthly sums of net CO 2 uptake by the canopy ( A nC ) were 13% higher than estimates based on eddy-covariance and chamber measurements. Annual estimates of A nC were only 3% higher than carbon (C) accumulations and losses estimated from ground-based measurements for the entire stand. The C budget for the Pinus taeda component was well constrained (within 1% of ground-based measurements). Although the closure of the C budget for the broadleaf species was poorer (within 20%), these species are a minor component of the forest. Under elevated CO 2 , the C used annually for growth, turnover, and respiration balanced only 80% of the A nC . Of the extra 700 g C m −2 a −1 (1999 and 2000 average), 86% is attributable to surface soil CO 2 efflux. This suggests that the production and turnover of fine roots was underestimated or that mycorrhizae and rhizodeposition became an increasingly important component of the C balance. Under elevated CO 2 , net ecosystem production increased by 272 g C m −2 a −1 : 44% greater than under ambient CO 2 . The majority (87%) of this C was sequestered in a moderately long-term C pool in wood, with the remainder in the forest floor–soil subsystem.