MINERAL TRANSFORMATION THROUGH FUNGAL WEATHERING

Ectomycorrhizal fungal weathering is well documented in soil environments and there is growing evidence from laboratory experiments that mineral dissolution rates are increased in the presence of ectomycorrhizal fungi. This process influences soil formation where the intermediate products are amorphous organo-clay materials that are possible pre-cursors for soil clay minerals.

This presentation highlights results from column growth experiments and field studies that focused on understanding processes at the plant-microbe-mineral interface. We investigated the role of biofilm and direct mineral surface contact of microbes in mineral weathering and secondary product formation. Plants provide the photosynthetic energy driving the weathering processes that result in nutrient release for immediate needs of the plants and microorganisms, and precipitation of secondary phases that provide sinks for unneeded elements and surfaces for nutrient accumulation. Combinations of chemical, biological, mineralogical, and computational techniques and methodologies are needed to untangle the complexity of the processes at the plant-microbe-mineral interface.

We utilized methods ranging from bulk to surface-specific techniques to examine transformations in batch, column, and mesocosm experiments. We estimated lithogenic elements weathered using amounts of cations in drainage and soil waters, plant biomass and soil exchangeable sites determined by ICP-AES, and characterized mineral surface changes such as etch-pit and secondary coating formations using scanning and transmission electron microscopy and atomic force microscopy methods. These techniques in combination with tracer studies, molecular microbiology methods and numerical geochemical modeling are being employed to improve our understanding of mineral transformations mediated by fungi.