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Quantification de l'effet des racines d'arbres et des microorganismes associés sur l'altération des minéraux de sols forestiers : observations en forêt et expérimentations

Abstract : The impact of the mineral weathering process on tree nutrition in acidic forest soils is well known. However, the quantitative effect of different biological factors on this process remains to be clarified. In this context, the aim of the present work was to quantify the impact of the rhizosphere of forest trees (roots and associated microorganisms) on the weathering of soil minerals. In forest, we observed an increase of the weathering of minerals (dissolution and transformation) in the rhizosphere of trees, suggesting an important impact of the tree rhizosphere on the dynamics of minerals as well as on soil evolution. We characterized in vitro the weathering potential of microorganisms which were isolated in forest from bulk soil and ectomycorrhizas. We showed that the ectomycorrhizal symbiosis significantly structures the functional diversity of culturable bacterial communities and selects strains potentially beneficial to tree nutrition. We developed a column experiment to quantify the respective impact of plant, bacteria and fungi on the weathering process. We demonstrated that tree roots and bacteria significantly increase Mg, K, Fe, Cs, Ni mobilisation via the weathering of a reference mineral. This process is altered in the presence of toxic elements such as uranium. Considering the whole of our results, we can propose the following hypothesis: in forest soils, the nutrient bioavailability determines the mineral weathering due to its impact on the root and microorganism activity. This suggests an important plasticity of forest ecosystems towards nutrition, which could partly explain the sustainability of these ecosystems.
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Submitted on : Friday, March 30, 2018 - 9:44:21 AM
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Christophe Calvaruso. Quantification de l'effet des racines d'arbres et des microorganismes associés sur l'altération des minéraux de sols forestiers : observations en forêt et expérimentations. Science des sols. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10129⟩. ⟨tel-01754308⟩

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