101-3 Biogeochemical Cycling and Mineral Weathering in Soil.
We observed differences in mineral weathering and soil chemical profiles between the studied angiosperm and gymnosperm tree systems in the field, which include understory vegetation, fungi, and bacteria. We assessed rooting depth and density, tree biomass, leaf chemical composition, and element accumulation and depletion patterns in soil beneath the different tree types. Complementary laboratory studies illuminated differences in mineral surface etching, organic acid exudation, litter decomposition, and rhizosphere pH. Using these data, we have developed a simple model that illustrates the biogeochemical cycles relating to the study trees. A deeper understanding of the differences in mineral weathering and biogeochemical cycling of elements will help us anticipate the impact of shifting vegetation and soil communities on modern soils as well as potential implications for the role of plants, fungi, and bacteria in the global long-term carbon cycle.
These studies provide a snapshot of the biogeochemical factors at work in soil processes, but additional methods are needed to determine the dynamics and feedback loops at play within the soil. One potential method, a colorimetric functional assay for small organic molecules with strong metal-chelating characteristics known as siderophores, will be presented.