Global comparison of mineral weathering rates by mycorrhiza

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Weathering is of utmost importance for the support of life on earth, as it delivers nutrients to organ-isms. Besides physico-chemical weathering, biogenic weathering might contribute substantially to overall mineral degradation and supply of nutrients to the ecosystem. Mycorrhizal fungi are in-creasingly identified to be a major player in biogenic weathering, but the underlying processes are still little understood as comparative in situ studies on large scale are lacking. This project aims at elucidating the biogenic weathering functioning of mycorrhizal fungi in a global field study by comparing forest ecosystems dominated by closely related plants either realizing arbuscular mycorrhiza (AM) or ectomycorrhiza (EM). Mesh bags containing minerals with different stability and nutrient contents are buried at 21 biogeochemically monitored sites for up to three years. Using multiple wet chemical, imaging, and spectroscopic methods we will assess (i) the extent of fungal colonization and type of mycorrhiza involved in mineral weathering, (ii) the selectivity, magnitude and rate of mycorrhiza-induced mineral weathering depending on ecosystem properties, and (iii) the contribution of different organism groups to biogenic weathering. This unique data set will largely extend our current understanding of the role of biota in ecosystem functioning and sustainability on global scale.