Document: KAR-3-32-25

Water use and stomatal conductance of Pinus taeda L. and Liquidambar styraciflua under ambient and elevated CO 2.

SCHAFER, K.V.R.*, R.OREN, C.LAI and G.KATUL

Duke University, Durham, NC 27708 USA 1

Abstract:
Plant water use was scaled from sap flux measured in a maturing loblolly pine forest at the FACTS-I (forest atmosphere transfer and storage) facility in the Duke Forest, NC, USA. Sap flux measurements of eight Pinus taeda and four Liquidambar styraciflua trees were made with Granier-type sensors at each of six clusters within the stand - three under ambient atmospheric CO2 (360 mol mol-1) and three under elevated CO2 (ambient + 200 mol mol-1) conditions. Canopy transpiration was estimated from sap flux measurements scaled with sapwood area per unit ground area for each species separately. Total stand transpiration agreed well with latent heat flux measured with the eddy-covariance technique. Mean canopy stomatal conductance was estimated for each species from transpiration and vapor pressure deficit. Stomatal conductance of both species were significantly lower under elevated than under ambient atmospheric CO2 under severe drought.

Keywords: Keywords; canopy conductance, water use, Pinus taeda , Liquidambar styraciflua

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This abstract is being presented at: 3:30 PM in session:
Oral Session #34: Water Relations in Trees.