Premium
Control of transpiration in an irrigated Eucalyptus globulus Labill. plantation
Author(s) -
White D. A.,
Beadle C. L.,
Worledge D.
Publication year - 2000
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.2000.00530.x
Subject(s) - transpiration , canopy , canopy conductance , eucalyptus globulus , eucalyptus , conductance , stomatal conductance , botany , interception , tree canopy , horticulture , mathematics , atmospheric sciences , environmental science , physics , biology , ecology , photosynthesis , combinatorics , vapour pressure deficit
Stomatal conductance and transpiration were measured concurrently in an irrigated Eucalyptus globulus Labill. plantation. Canopy stomatal conductance, canopy boundary layer conductance and the dimensionless decoupling coefficient ( Ω ) were calculated (a) summing the conductance of three canopy layers ( g c ) and (b) weighting the contribution of foliage according to the amount of radiation received ( g c ′). Canopy transpiration was then calculated from g c and g c ′ for Ω = 1 ( E eq ), Ω = 0 ( E imp ) and by weighting E eq and E imp using Ω ( E Ω ). E eq , E imp and E Ω were compared to transpiration estimated from measurements of heat pulse velocity. The mean value of Ω was 0·63. Transpiration calculated using g c and assuming perfect coupling (12·5 ± 0·9 mmol m −2 s −1 ) significantly overestimated measured values (8·7 ± 0·8 mmol m −2 s −1 ). Good estimates of canopy transpiration were obtained either (a) calculating E Ω separately for the individual canopy layers or (b) treating the canopy as a single layer and using g c ′ in a calculation of E imp ( Ω = 0). The latter approach only required measurement of stomatal conductance at a single canopy position but would be unsuitable for use in combined models of canopy transpiration and assimilation. It should however, be suitable for estimating transpiration in forests regardless of the degree of coupling.