Has the Priestley-Taylor Equation Any Relevance to Forest Evaporation?

Abstract Long-term evaporation measurements are expressed in the Priestley-Taylor (1972) “Potential evaporation” framework for a spruce forest in Plynlimon, Wales, and a Scots Pine forest in Norfolk, England. The results are used to illustrate the possibility of significant variability in evaporation from forest vegetation in response to precipitation input, and so provide a warning against the indiscriminate use of the Priestley-Taylor formula. A tentative suggestion is made regarding a possible role for potential evaporation in the forest environment.