5. Prof. Dan Yakir

Evapotranspiration (ET) is considered the key means of controlling leaf and ecosystem temperature. Under dry conditions, ET is greatly suppressed, temporally and in the total water availability. Yet, vegetations succeed in keeping leaves and canopies within the physiological limits of about 35C, which becomes increasingly important for survival under climate change. We show that this relies on shifting the dominant underlying temperature management processes from those relying on “water cooling” (evaporation) to those relying on “air cooling (turbulence).” A critical component in this shift is the enhanced production of sensible heat flux, which requires changes in the aerodynamic resistance to heat transfer. We briefly discuss the evolution of this process from the leaf through branches to the canopy scale. We also argue that the contribution of sensible heat fluxes to heat dissipation, and its contribution to vegetation temperature management is often underrated in general and not only in dry conditions.