One significant component of the surface and energy budget of a tall forest is the total heat storage (c. 5–10% of net radiation) which is affected by humidity, air temperature and the biomass of the canopy and the stem (e.g. Moore & Fisch, 1986). Approximately 80 W m−2 of maximal absolute hourly biomass heat storage fluxes were obtained for a 35-m-tall Amazonian tropical forest (Moore & Fisch, 1986) and similar values for a 30-m-tall Eucalyptus forest in Western Australia (Silberstein et al., 2001), while 63 W m−2 was reported for a 40-m-tall Eucalyptus forest in Eastern Australia (Haverd et al., 2007). In such cases, the absorption of net radiation by the canopy during the daytime and heat storage by the stem are important. The change in biomass heat storage is driven by radial heat diffusion within the stems and surface heat exchange by convection, insolation and longwave radiation (Haverd et al., 2007). In the early morning, the heat storage of air is maximal, corresponding to a rapid change of temperature. Radiative heat exchange with the environment takes place at the top of the canopy, and radiative energy is transferred slowly to the lower levels of stems because of their thermal properties, with a thermal conductivity 10-fold higher and a specific heat capacity 2-fold higher than that of air (Aston, 1985; Moore & Fisch, 1986; Haverd et al., 2007). More rapidly, the sun evaporates water from the canopy, which is carried down by turbulent air, promoting warm humid air in the understorey (e.g. Moore & Fisch, 1986). This process leads to warmer ambient air temperatures and cooler stem and bark temperatures during the daytime, a phenomenon that continues sometimes until late afternoon. This principle of delayed warming of stems in comparison to ambient air is not restricted only to tall forests (Aston, 1985; Moore & Fisch, 1986; Haverd et al., 2007); it has also been reported for a mixed 19-m-tall forest in Ontario, Canada (McCaughey, 1985) and for a 10-m-tall walnut (Juglands regia) orchard in California, USA (Garai et al., 2010). Thus, a colder stem temperature in the morning seems to be a common phenomenon, and may drive dew formation on the bark and epiphytic organisms under specific environmental conditions world-wide.