『Abstract
　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』

『要旨
　地衣類とその岩石基質との境界についての多数の調査によって提供された証拠は、鉱物の風化が少なくともいくつかの地衣類種の成長により促進されえることを示している。地衣類の鉱物基質に対する影響は、物理と化学の両方の過程に起因しうる。物理的影響は、菌糸の侵入、地衣類葉状体の膨張と収縮、および地衣類活動から生じる有機・無機塩の膨潤作用が引き起こす岩石の機械的な崩壊により反映される。地衣類はさまざまな有機酸、とくに鉱物を効果的に溶解できて金属イオンと結合してキレートをつくれるシュウ酸を排出することで、岩石の化学風化にも重要な影響を与える。地衣類により引き起こされる風化の結果、多くの造岩鉱物は広範囲にわたる表面腐食を示す。結晶度の低い鉄酸化物と非晶質のアルミノ珪酸ゲルの沈殿、結晶質金属シュウ酸塩と二次粘土鉱物の生成は、天然で地衣類のコロニー形成があるさまざまな岩石でしばしば確認されている。環境への地衣類の影響をもっと理解するためには、天然岩石の風化、建造石材と石造物の劣化、および初生土壌の形成に与える地衣類の影響の包括的な関係についてもっと研究が行われる必要がある。』

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
References