Energy budget evaluation of the transpiration‐<i>p</i>F relationship in a young pine forest

Abstract

By using the Bowen ratio method, hourly and daily evapotranspiration totals were determined during a drying period for a 9‐year‐old pine forest ( Pinus sylvestris ) situated in the upper Rhine area of Germany. A relationship between the soil water suction, expressed by p F, and the ratio Q of the latent heat of evapotranspiration to the available energy was obtained. For 2 &lt; p F &lt; 3, Q ≈ 0.6, and for p F &gt; 3, Q decreases exponentially when p F increases. For p F ≈ 4.2, Q = 0.11. These and other empirical and theoretical results discussed in the paper suggest that the Q − p F relationship can be useful for calculating evapotranspiration from complex terrain situations where the micrometeorological approach is inapplicable.