title: Elevated carbon dioxide does not affect average canopy stomatal conductance of Pinus taeda L.
abstract: While photosynthetic responses of C3plants to elevated CO2are fairly well documented, whole-plant water use under such conditions has been less intensively studied. Woody species, in particular, have exhibited highly variable stomatal responses to high CO2as determined by leaf-level measurements. In this study, sap flux of Pinus taeda L. saplings was periodically monitored during the 4th year of an open-top chamber CO2fumigation experiment. Water use per unit sapwood area did not differ between treatments. Furthermore, the ratio of leaf area to sapwood area did not change under high CO2, so that average canopy stomatal conductance (on a unit leaf area basis) remained unaffected by the CO2treatment. Thus, the only effect of high CO2was to increase whole-plant water use by increasing sapling leaf area and associated conducting sapwood area. Such an effect may not directly translate to forest-level responses as the feedback effects of higher leaf area at the canopy scale cannot be incorporated in a chamber study. These feedbacks include the potential effect of higher leaf area index on rainfall and light interception, both of which may reduce average stomatal conductance in intact forest canopies.
authors.affiliation: Nicholas School of the Environment, Duke University, Durham, NC 27708, USA, , , , , , US.
authors.forename: Diane E
authors.initials: DE
authors.lastname: Pataki
authors.affiliation: Nicholas School of the Environment, Duke University, Durham, NC 27708, USA, , , , , , US.
authors.forename: Ram
authors.initials: R
authors.lastname: Oren
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA, , , , , , US.
authors.forename: David T
authors.initials: DT
authors.lastname: Tissue
keywords: Elevated CO2; Key wordsPinus taeda; Stomatal conductance; Whole-plant water use