16 June 2024

Foliose lichens – Raydah Escarpment

The climate of Raydah and the general area of Jebel Sawdah near Abha is influenced both by westerly depressions which bring rain in the winter and spring, and by the southwest monsoon system which brings summer precipitation averaging of 559 mm of rainfall per year. In addition, the Red Sea diurnal wind circulation brings frequent cloud to areas above 1000m, allowing the growth of foliose lichens on trees. Foliose lichens are abundant on the trees above 2500 m but there are few or no lichens below 2350m showing how the cloud moisture at the top of the Raydah Escarpment helps sustain this plant.