See more from this Division: Topical Sessions
See more from this Session: Opportunities at the Interface: Minerals, Bugs, and Aqueous Solutions
Abstract:
We studied the effects of ectomycorrhizal fungus and bacteria associations with a growing pine seedling root system, on mineral surface alteration, weathering fluxes, and the partitioning of weathering products, in simple replicated flow-through column systems. Tree-system soil waters exhibited 20-60% lower concentrations than controls without trees, and the tree systems showed correspondingly smaller drainage losses. Mineral weathering fluxes, which were largely diverted into soil and biomass pools, were greatest in fungus + bacteria treatments. Microscopy showed widespread microbe-mineral attachment via extracellular polysaccharides (EPS) which blanketed etched mineral surfaces. The same phenomena, including suppression of soil-water nutrient concentrations, were observed in the five-order-magnitude larger Hubbard Brook sandbox mesocosms growing 15-20 yr old pine trees.
These results are consistent with a mycorrhizosphere chemical-weathering model in which mineral, microbe, solution, and root interfaces coexist in micron to sub-micron proximity inside bacterially generated EPS biofilms. Within these biofilms, acid and ligand generation, mineral dissolution, and plant uptake mass transfers can occur a) over very small distances, and b) in relative isolation from bulk soil water, thereby increasing plant nutrient acquisition efficiency and reducing drainage loss.
See more from this Division: Topical Sessions
See more from this Session: Opportunities at the Interface: Minerals, Bugs, and Aqueous Solutions