Pedogenetic action of the lichens Lecidea atrobrunnea, Rhizocarpon geographicum gr. and Sporastatia testudinea on serpentinized ultramafic rocks in an alpine environment

The effects of biogeophysical and biogeochemical weathering generated by the epilithic lichen species Sporastatia testudinea (Ach.) A. Massal., Lecidea atrobrunnea (Lam. and DC.) Schaer. and Rhizocarpon geographicum gr. on antigorite serpentinites were examined with a petrographic and lichenological approach. Lithotype structure and mineral composition are decisive factors in modulating hyphal penetration which invades up to 2 mm in depth. A microcrystalline fraction composed of fragments of the colonized substratum (antigorite, magnetite, diopside), neoformation minerals typical of serpentine soils (illite, halloysite, vermiculite) and biomineralization products (mainly oxalates), constantly found at the lichen-rock interface, underlines the important role of these crustose lichen species in the pedogenetic processes.