Observations of equilibrium evaporation from a windbreak-sheltered kiwifruit orchard

K. J. McAneney*, P. T. Prendergast, M. J. Judd, A. E. Green

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

Eddy correlation measurements of sensible heat and evaporation fluxes from a kiwifruit orchard confirm earlier, less comprehensive measurements that the spatially-averaged evaporation rate from well-watered and well-sheltered orchard blocks in the northern part of New Zealand occurs at the equilibrium rate (Eq. In this humid coastal climate the rapid onset of dewfall after sunset prevents night-time water use, which contrasts with other work showing that nocturnal transpiration may represent 25% of the daily water economy of a kiwifruit vine. Sensible heat fluxes measured at both shelter height (h) and 2.25h agreed within 5%, implying the existence of a constant flux region above shelter height. Under the low windspeed conditions common in mid-summer, the aerodynamic resistance to scalar transport between the canopy and the height of the windbreaks is shown to be of comparable magnitude (about 65 s m-1) to both the canopy 'stomatal' and boundary-layer resistances. One consequence of this is that transpiration will be less sensitive to stomatal regulation. Independent of imposed wind and radiative conditions, the effect of the close-spaced windbreaks and crop geometry is to create an orchard environment that is an efficient absorber of radiation but which is relatively poorly coupled with overhead conditions through turbulent exchange.

Original languageEnglish
Pages (from-to)253-264
Number of pages12
JournalAgricultural and Forest Meteorology
Volume57
Issue number4
DOIs
Publication statusPublished - 1992
Externally publishedYes

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