- journal_title：Geology
- Contributor：Steeve Bonneville ; Mark M. Smits ; Andrew Brown ; John Harrington ; Jonathan R. Leake ; Rik Brydson ; Liane G. Benning
- Publisher：Geological Society of America
- Date：2009-
- Format：text/html
- Language：en
- Identifier：10.1130/G25699A.1
- journal_abbrev：Geology
- issn：0091-7613
- volume：37
- issue：7
- firstpage：615
- section：Articles
Plant-driven fungal weathering is a major pathway of soil formation, yet the precise mechanism by which mycorrhiza alter minerals is poorly understood. Here we report the first direct in situ observations of the effects of a soil fungus on the surface of a mineral over which it grew in a controlled experiment. An ectomycorrhizal fungus was grown in symbiosis with a tree seedling so that individual hyphae expanded across the surface of a biotite flake over a period of three months. Ultramicroscopic and spectroscopic analysis of the fungus-biotite interfaces revealed intimate fungal-mineral attachment, biomechanical forcing, altered interlayer spacings, substantial depletion of potassium (~50 nm depth), oxidation of the biotite Fe(II), and the formation of vermiculite and clusters of Fe(III) oxides. Our study demonstrates the biomechanical-chemical alteration interplay at the fungus-biotite interface at the nanometer scale. Specifically, the weathering process is initiated by physical distortion of the lattice structure of biotite within 1 μm of the attached fungal hypha. Only subsequently does the distorted volume become chemically altered through dissolution and oxidation reactions that lead to mineral neoformation.