Boreskov

OP‐27lichenized fungi to tolerate severe abiotic stresses such as dessication, rapid rehydration,temperature extremes and high UV light intensities (Nash, 2008). Lichens are often pioneerson rocky surfaces and are well known for accelerating mineral weathering. Besides, lichenscolonizing fine‐earth or disturbed soil often act as stabilizers of their substrate preventingsurface erosion. Lichens can contribute to primary accumulation of soil organic matter viaproducts of thalli decomposition or leached‐off phenolic and nitrogenous compounds. Theyalso produce laccases and tyrosinases which are well known catalysts of polyphenolspolymerization into humic substances (Laufer et al 2006 ab, Zavarzina and Zavarzin, 2006).According to the first fossil records lichens colonized soil in Ordovician‐Silurian (480‐400Ma). This time might be considered as the beginning of the formation of organic‐mineralsoil.76