Establishment of pioneer litho-microorganisms on chalk rocks after a severe forest fire in Israel

Three and a half years after a forest fire in the Carmel Mountains, Israel, we observed, on chalk rocks, ascocarps of the non-lichenized ascomycete Didymella applanata which is considered to be the first visible pioneer on such rocks following a forest conflagration. Four years after the fire, we observed unicellular green algae on burnt surfaces of the rocks, probably Trebouxia sp., colonizing small holes 30-50 μm in diameter, and clusters of ascospores of the lichens Caloplaca aurantia and Xanthoria parietina located in small rock depressions. Young thalli of the lichen Xanthoria parietina colonized fissures on the rock surfaces. The first thalli of crustose lichens which were observed on rocks 4 years after the fire were Caloplaca aurantia.