Evapotranspiration of Melaleuca Forest in South Florida

Abstract

Melaleuca forests cover extensive areas of south Florida, and are widely assumed to have extraordinarily high evapotranspiration (ET) rates. This investigation indicates that the transpiration of the melaleuca forest is dominated by vapor deficits, with net radiation playing a secondary role. Evaporation of intercepted rainfall contributes between 12 and 23% to the monthly ET, with lower contributions during the dry season and higher contributions during the wet season. Annual ET from the melaleuca forest is estimated to be approximately 1,600 mm, with 300 mm contributed by intercepted rainfall. Comparison of these results with predictions of other forest-ET models indicate that the Shuttleworth model overestimates the ET of melaleuca forest by about 5% in a typical month as a result of neglecting the canopy wetness effect. The Clader-Newson model, which equates forest transpiration to short-vegetation transpiration, produces annual ET estimates that are within 6% of the annual ET estimated in this study. However, the discrepancies in monthly ET range between -8 and +17%.