Mineral tunnelling weathering

Smits, M., Hoffland, E. van Breemen, N. (2005). Contribution of mineral tunneling to total feldspar weathering. Geoderma, 125, 59-69. 

The absence of secondary mineral precipitation in fungal tunnels indicates that the weathering products are removed from the tunnel interior, either by diffusion or fungal transport. Removal by diffusion is likely because it is probably faster than feldspar weathering. If the tunnel is occupied by a fungus, the diffusion rate would be depressed, so that fungal transport could become important. 

Production of organic acids by EMF has also been suggested to result in penetration of mineral particles by EM hyphae (Jongmans et al., 1997), although recent estimates have found that tunnel-shaped structures within mineral grains contribute very little (less than 1 %) of the total weathering in the soil (Smits et al., 2005 see Smits, Chapter 13 this volume). 

EM fungi can also get hold of nutrients from rock mineral by active weathering of rock minerals. The fungus might even do this from rather inert rock materials like granite where it has been shown that mycorrhizal fungi can etch tunnels through the stone mineral (Fig 6.7 and 6.8). 

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