title: Transpiration from a mature Eucalyptus globulus plantation in Portugal during a spring-summer period of progressively higher water deficit.
abstract: The rates of transpiration from a mature Eucalyptus globulus Labill. stand in Portugal were evaluated during a drying period of the spring-summer 1994. Transpiration was measured by the Granier sap flow method and estimated by the Penman-Monteith model. During the experimental period daily transpiration varied between 3.64 and 0.50 mm day-1. For high-transpiration days, a good agreement was observed between Penman-Monteith estimates and sap flow measurements, both on a daily and on an hourly basis. However, for low-transpiration days, the Penman-Monteith model overestimated transpiration in comparison with the sap flow method. The diurnal variation of sap flow was then smoother and lagged behind the estimates of the Penman-Monteith model. E. globulus showed an efficient control of transpiration losses during dry periods through a progressive stomatal closure. As soil moisture deficit increased, the daily maximum stomatal conductance decreased from 0.46 to 0.14 cm s-1. The results also show that, on a seasonal basis, stomatal conductance and daily transpiration were mainly related to predawn leaf water potential and, thus, to soil moisture content.
authors.affiliation: Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa Codex, Portugal fax: 00 351 1 3645000; e-mail: Prostep@isa.utl.pt, , , , , , PT.
authors.forename: T S
authors.initials: TS
authors.lastname: David
authors.affiliation: Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa Codex, Portugal fax: 00 351 1 3645000; e-mail: Prostep@isa.utl.pt, , , , , , PT.
authors.forename: M I
authors.initials: MI
authors.lastname: Ferreira
authors.affiliation: Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa Codex, Portugal fax: 00 351 1 3645000; e-mail: Prostep@isa.utl.pt, , , , , , PT.
authors.forename: J S
authors.initials: JS
authors.lastname: David
authors.affiliation: Instituto Superior de Agronomia, Tapada da Ajuda, 1399 Lisboa Codex, Portugal fax: 00 351 1 3645000; e-mail: Prostep@isa.utl.pt, , , , , , PT.
authors.forename: J S
authors.initials: JS
authors.lastname: Pereira
keywords: Key words Transpiration ;   Water deficit;  Eucalyptus globulus Sap flow 