Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Experimental weathering of mica by mycorrhizal and non-mycorrhizal beech and pine. | 762s Ann. Sci. For. 1989 46 suppl. 762s-764s Forest Tree Physiology E. Dreyer etal. eds. Elsevier INRA Experimental weathering of mica by mycorrhizal and non-mycorrhizal beech and pine c. Leyval and J. Berthelin Centre de Pédologie Biologique du CNRS 17 rue BP 5 54500 Vandoeuvre-lồs-Nancy France Introduction Ectomycorrhizal fungi are able in pure culture to release organic acids and to solubilize insoluble minerals such as insoluble phosphates Leyval and Berthelin 1986 . However in symbiotic conditions in plant rhizosphere their effect on the weathering of minerals has not yet been studied to any great extent. A lysimeter experiment was performed in a greenhouse to study the influence of Laccaria laccata mycorrhization on the weathering of phlogopite a ferro-magnesian mica in pine Pinus sylvestris L. and beech Fagus silvatica L. rhizospheres. Materials and Methods Six month old pine and beech seedlings were grown on sand in lysimetric cylinders Leyval 1988 1989 . They were inoculated or not with the ectomycorrhizal fungus L. laccata. Phlogopite particles mixed with the sand were the only source of Mg Fe and Al and the partial source of K for plant nutrition. Cylinders with plants and control cylinders without plants were fed automatically with a nutrient medium. After 2 yr dry weight of plants and their uptake of mineral elements were determined Ley-val 1988 1989 . Phlogopite transformation was observed by means of chemical analyses X-ray diffraction analysis and scanning electron microscopic observations combined with a microprobe Leyval 1988 . Mineral element Mg Fe and Al mobilization from phlogopite was indirectly evaluated by adding the quantities absorbed by plants and the amounts released in the collected nutrient solution. Results X-ray diffraction diagrams Fig. 1 show a mineralogical transformation of phlogopite into the clay vermiculite appearance of a peak at 14 Â . This transformation was observed only in the rhizosphere and was greater
