Abstract

Although the processes governing photosynthesis are well understood, scaling from shoot to canopy in coniferous forests is complex. Development of different sap-flow techniques has made it possible to measure transpiration of whole trees and thereby also of whole canopies. There is a strong link between photosynthesis and transpiration, For which reason it would be interesting to test whether measurements of canopy transpiration could also be used to estimate canopy photosynthesis. As a first step towards this, water-use efficiency (WUE) was studied at branch and canopy scales on the basis of branch gas-exchange measurements, with half-hourly and daily temporal resolution. Half-hourly and daily WUE at both branch and canopy scales showed a strong dependency on vapour-pressure deficit (deltae). Branch photosynthesis modelled from branch transpiration and deltae mimicked well measured branch photosynthesis. Also, modelled photosynthesis, scaled to canopy and compared to net forest CO2 exchange measured by the eddy-covariance technique, occasionally showed good agreement. In spite of these seemingly promising results, there was a difference in the response to deltae between branches and between years, which needs to be better understood

Published in

Trees - Structure and Function
2001, Volume: 15, number: 2, pages: 67-74
Publisher: SPRINGER-VERLAG

SLU Authors

• Moren, Ann-Sofie

  • Department of Forest Soils, Swedish University of Agricultural Sciences
    

• Grelle, Achim

  • Department of Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Forest Science
Environmental Sciences related to Agriculture and Land-use
Renewable Bioenergy Research


Publication identifier

DOI: https://doi.org/10.1007/s004680000078

Permanent link to this page (URI)

https://res.slu.se/id/publ/23953