ABSTRACT
Much controversy has arisen over the years regarding the ability of saxicolous lichens to degrade their rock substrates, thus leading to the first stages in the formation of soil. The biological weathering of rocks and their constituent minerals involves both biogeochemical and biogeophysical weathering processes. The suggestion was made that, in this instance, the action was chemical since the etching was distributed evenly below older lichens, but was absent on the rock over which the younger thalli were growing. Schatz emphasized that the hyphae of crustose saxicolous lichens are in intimate contact with mineral particles and that the lichen acids are extracellular, crystallizing out on hyphae where they can act directly on rock minerals. The vegetation cover of the soils analyzed were lichens, mixed spruce/lichens, and spruce. The interpretation of this finding was that, once more, oxalic acid was implicated in the reaction of the lichen with the substrate rock.
