Abstract:
• Additional water supplied by dew formation is an important resource for microbes, plants
and animals in precipitation-limited habitats, but has received little attention in tropical forests
until now.
• We evaluated the micro-environmental conditions of tree stem surfaces and their epiphytic
organisms in a neotropical forest, and present evidence for a novel mechanism of diurnal dew
formation on these surfaces until midday that has physiological implications for corticolous
epiphytes such as lichens.
• In the understorey of a lowland forest in French Guiana, heat storage of stems during the
day and delayed radiative loss during the night decreased stem surface temperatures by 6?C
in comparison to the dew-point temperature of ambient air. This measured phenomenon
induced modelled totals of diurnal dew formation between 0.29 and 0.69 mm d
)1
on the
surface of the bark and the lichens until early afternoon.
• Crustose lichens substantially benefit from this dew formation, because it prolongs photo-
synthetic activity. This previously unrecognized mechanism of midday dew formation contrib-
utes to the water supply of most corticolous organisms, and may be a general feature in forest
habitats world-wide
