The Effects of Landscape and Soil Development on the Terrestrial Phosphorus Cycle

Indiana University, Bloomington IN

Investigators

Abstract

Previous research has yet to quantitatively document how past climates, especially glacial-interglacial cycles, have affected the release of phosphorus from continental material and/or the availability of phosphorus to terrestrial and marine ecosystems. As a biolimiting nutrient, phosphorus availability plays a key role in reconstructions of the biological cycle and the global carbon balance. The major focus of this research project will be a comprehensive examination of phosphorus geochemistry in lake sediments as a record of soil development in surrounding landscapes since deglaciation. New perspectives gained from studies of lake-sediment records promise to add a solid geologic component to understandings of the effects of climate and landscape development on the terrestrial phosphorus cycle. This research will be performed on sediment cores from a variety of headwater lakes in North America, spanning a range of paleoclimates, bedrock lithologies, slope-aspect characteristics, and ecosystem types. The project also will include an assessment of phosphorus transformations along a transect of lakes. This will allow characterization of changes in phosphorus availability and assessment of the impacts on the phosphorus geochemical record from external input (soil and litter weathered from surrounding watersheds) and internal production (organic matter production and deposition from dissolved phosphate in the lake-river systems and the effects of sediment diagenesis). The project also will include examination of several other potential paleoweathering indicators in these lakes, including clay mineralogy, organic matter and carbon-nitrogen-phosphorus ratios, phosphorus-aluminum ratios, and germanium-silicon ratios of lake diatoms using a recently developed technique. Results from this project will add a critical terrestrial dimension to reconstructions of the global phosphorus mass balance. It will shed new light on the biogeochemistry of phosphorus fluxes into oceanic environments over time, and it will provide quantitative information about the state of nutrient dynamics on the continents as a function of climate.