MS, Kent State University, 2019, College of Arts and Sciences / Department of Earth Sciences
Manganese (Mn), an essential nutrient critical for photosynthesis in plants but a toxic
element in excess, impacts the fate and transport of other nutrients and toxins, forest metabolism,
carbon storage, and ecosystem productivity. Given the significant role Mn can play in
ecosystems, it is important to understand how soil geochemistry controls Mn uptake by
vegetation. The purpose of this research was to explore how Mn uptake by plants is related to
Mn supply to plants through mineral dissolution. We conducted a greenhouse pot experiment to
quantify Mn uptake by plants based on controlled geochemical constraints. Specifically, we
investigated whether Mn uptake was limited by the supply of Mn to soil solution or by biological
controls within the plants. Greenhouse soil pots (quartz sand + peat) that were non-vegetated or
vegetated with red maple saplings were supplied with either no added Mn, dissolved Mn, Mn
oxides, or crushed shale containing Mn-bearing pyrite. We analyzed the chemical composition of
plant tissue to quantify Mn uptake and soil leachate to quantify Mn losses. From these values, we
constructed a mass balance model and calculated pseudo-first order rate constants to compare
Mn mobilization between treatments. Mn uptake was higher in systems with dissolved Mn
because it was not limited by mineral weathering. Mn uptake was also higher in systems supplied
with fast-weathering substrates (pyrite in the shale) than slow-weathering substrates (Mn
oxides). There were not significant differences in Mn leaching and total Mn loss between
vegetated and non-vegetated pots in the Mn-oxide or shale treatments. We conclude that Mn
uptake is controlled by dissolution rates of Mn-minerals in soil.
Committee: Elizabeth Herndon (Advisor); David Singer (Committee Member); Chris Blackwood (Committee Member)
Subjects: Biogeochemistry; Environmental Geology; Environmental Science; Environmental Studies; Geobiology; Geochemistry; Geology