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| on dynamics in the rhizo- and mycosphere |
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F. Beese
Institut für Bodenkunde und Waldernährung, Göttingen
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Soils in general are characterized by bulk parameters like texture, pH, cation exchange capacity, base saturation, organic matter etc. Based on empirical studies, these parameters are optimized by soil management reducing possible physical and chemical stress in the root zone to obtain maximal growth or yields.
These parameters however do not describe the environment the root or in case of mycorrhized roots the fungi "see" in the soil. Due to water- and nutrient uptake or ion discrimination and exudation, spatial and temporal changes occur in the rhizo- and mycosphere, which dramatically may differ from the chemical situation of the bulk soil. This may lead to chemical stress to roots and fungi, not obvious when regarding chemistry of the bulk soil matrix or bulk soil solution.
Based on a multi species nutrient uptake model and studies of the rhizosphere chemistry of trees in acid soils, insight will be given in the dynamics of ions in the root/soil interface. It will be demonstrated that it is essential in nutrient uptake studies to include the dynamics of the physical and chemical interactions in the porous medium soil. Moreover it is necessary to regard not only the behaviour of one or two ions, but also the whole spectrum of cat- and anions involved. Another important aspect is the change in water content of the soil and the specific rate of water uptake by roots and fungi, which have impact on the chemical gradients built up in the root environment, leading to temporal chemical stress and influencing the metabolism and growth of plants.
Experimental and model results will be presented and discussed with respect to research needs and soil management in the future.
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