Articles
USE OF SAP-FLOW PROFILES IN TRUNKS TO DERIVE CANOPY CONDUCTANCE
Article number
846_30
Pages
271 – 276
Language
English
Abstract
We have tested the hypothesis that if sap flow in the outer rings changes as a consequence of stomatal response to environmental variables, then we can infer canopy conductance from sap-flow measurements.
In 2004 we ran experiments to calibrate the tz compensation heat-pulse method in three fruit tree species with contrasting hydraulic characteristics and water requirements: olive, plum and orange.
In some of those experiments one tree of each species was cut at ground level and the butt placed in a reservoir with free water.
Then we measured the actual tree transpiration (Ep) every half hour, as well as the total leaf area.
The Ep values, together with simultaneous measurements of micrometeorological variables over the trees, were used to calculate reliable values of canopy conductance by inverting the Penman-Monteith equation (Gc). We also obtained independent values of canopy conductance from leaf gas-exchange measurements carried out in the three instrumented trees (gc), and checked that they were similar to the Gc results.
Our gc data were compared to tz profiles recorded in the trunk to test our hypothesis that the diurnal pattern of tz profiles can be used to derive reliable values of canopy conductance.
Results from the three tested species showed a good correlation between tz and gc, thus confirming our hypothesis.
In 2004 we ran experiments to calibrate the tz compensation heat-pulse method in three fruit tree species with contrasting hydraulic characteristics and water requirements: olive, plum and orange.
In some of those experiments one tree of each species was cut at ground level and the butt placed in a reservoir with free water.
Then we measured the actual tree transpiration (Ep) every half hour, as well as the total leaf area.
The Ep values, together with simultaneous measurements of micrometeorological variables over the trees, were used to calculate reliable values of canopy conductance by inverting the Penman-Monteith equation (Gc). We also obtained independent values of canopy conductance from leaf gas-exchange measurements carried out in the three instrumented trees (gc), and checked that they were similar to the Gc results.
Our gc data were compared to tz profiles recorded in the trunk to test our hypothesis that the diurnal pattern of tz profiles can be used to derive reliable values of canopy conductance.
Results from the three tested species showed a good correlation between tz and gc, thus confirming our hypothesis.
Publication
Authors
A. Diaz-Espejo, J.E. Fernández
Keywords
olive, plum, orange, sap flow profiles, transpiration, stomatal conductance
Online Articles (44)