Chen,J., Blume,H.-P. and Beyer,L.(2000): Weathering of rocks induced by lichen colonization - a review. Catena, 39, 121-146.


 The evidence presented by numerous investigations of the interface between lichens and their rock substrates strongly suggests that the weathering of minerals can be accelerated by the growth of at least some lichen species. The effects of lichens on their mineral substrates can be attributed to both physical and chemical processes. The physical effects are reflected by the mechanical disruption of rocks caused by hyphal penetration, expansion and contraction of lichen thallus, swelling action of the organic and inorganic salts originating from lichen activity. Lichens also have significant impact in the chemical weathering of rocks by the excretion of various organic acids, particularly oxalic acid, which can effectively dissolve minerals and chelate metallic cations. As a result of the weathering induced by lichens, many rock-forming minerals exhibit extensive surface corrosion. The precipitation of poorly ordered iron oxides and amorphous alumino-silica gels, the neoformation of crystalline metal oxalates and secondary clay minerals have been frequently identified in a variety of rocks colonized by lichens in nature. For a better understanding of the impacts of lichens on environments, further work on the comprehensive involvement of the lichen effects on weathering of natural rocks, deterioration of building stones and stonework, and formation of primitive soils should be carried out.

Keywords: Lichens; Lichen acids; Mineral substrates; Weathering process』


1. Introduction
2. Physical effects
 2.1. Penetration of hyphae
 2.2. Expansion and contraction of thallus
 2.3. Freezing and thawing of lichen thallus and associated microenvironment
 2.4. Swelling action of organic ad inorganic salts
 2.5. Incorporation of mineral fragments into thallus
3. Chemical effects
 3.1. Mechanisms
  3.1.1. Respiratory CO2
  3.1.2. Oxalic acid
  3.1.3. Lichen compounds
  3.1.4. Other mechanisms
 3.2. Nature of weathered rocks and minerals
  3.2.1. Sandstone
  3.2.2. Basalt
  3.2.3. Granitic rocks
  3.2.4. Calcareous rocks
  3.2.5. Other rocks
 3.3. Secondary weathering products
  3.3.1. Metal oxalates
  3.3.2. Iron oxides
  3.3.3. Amorphous alumino-silicate gels
  3.3.4. Clay minerals
4. Further areas of research
 4.1. Involvement of lichens in weathering and preliminary soil-forming processes
 4.2. Weathering rate of rocks promoted by lichen
 4.3. Involvement of airborne dusts
 4.4. Protection effects of lichen against weathering process