Branch transpiration of pine and spruce scaled to tree and canopy using needle biomass distributions |
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Authors: | A-S Morén Anders Lindroth Jeremy Flower-Ellis Emil Cienciala Meelis Mölder |
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Institution: | (1) Department for Production Ecology, Swedish University of Agricultural Sciences, P.O. Box 7042, SE-750 07 Uppsala, Sweden e-mail: Ann-Sofie.Moren@spek.slu.se Tel.: +46-18-672559, Fax: +46-18-673376, SE;(2) Department of Physical Geography, University of Lund, P.O. Box 118, SE-22100 Lund, Sweden, SE;(3) Department of Soil Sciences, Swedish University of Agricultural Sciences, P.O. Box 7014, SE-75007 Uppsala, Sweden, SE |
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Abstract: | Branch water exchange and total tree water uptake were measured in a mixed Norway spruce and Scots pine stand in central Sweden
during the 1995 and 1996 growing seasons. Branch transpiration was scaled to canopy level on the basis of a branch conductance
model, using vertical needle-area distributions obtained by destructive sampling. Comparison with total tree water uptake
scaled to canopy level showed agreement within 10%, for periods when the canopy was not affected by climatically induced stress.
Comparison of scaled fluxes on individual trees showed that measurements of transpiration at branch level provide information
on the direct response of transpiration to variations in weather, and furthermore that the time-lag between transpiration
and tree water uptake was as much as 3 h. The vertical needle-area distribution of Scots pine was similar to that found by
other authors. Needle-area distribution on Norway spruce, which has not been described before, showed that it has its largest
needle area at the top of the crown. Specific needle area varied considerably both within trees and between trees. For spruce,
mean specific needle area (±SD) varied from 2.4±0.5 mm2 mg–1 at the top of the crown to 7.1±1.9 mm2 mg–1 at the base. Corresponding figures for Scots pine were 3.4±2.0 and 9.1±2.1.
Received: 5 March 1999 / Accepted: 17 March 2000 |
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Keywords: | Boreal forest Norway spruce Scots pine Sap-flow Allometric relationships |
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