Effects of lichens on the geochemical weathering of granitic rocks

This paper examined the role of lichens in geochemical weathering of granite for several lichens representative of the species colonizing granitic monuments in Galicia (N.W. Spain). The salient results were that although the lichens affected the mobility of some elements, overall geochemical weathering was similar for colonized and uncolonized rock. Where differences were detected the various lichen species generally had similar effects on the weathering of the rock. Lichens seemed to protect the exposed surface of the rock from atmospheric weathering, thereby reducing losses of the most mobile elements. However, the overriding factor determining the extent to which an element was accumulated at, or mobilized from, the surface of colonized rock was the susceptibility to weathering of the source mineral. A new term, “interphase”, was introduced to describe rock engulfed in lichen thalli.