The Geochemical Carbon Cycle: A Vadose-Hydrologic Study of the Effect of Plants on Weathering

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9508003 Keller Carbon dioxide (CO2) is a greenhouse gas. One avenue to understanding the relationship of atmospheric CO2 concentration to climate, is to study processes affecting atmospheric CO2 on long time scales. The principal pathway for long-term transfer of CO2 from Earth's atmosphere to its crust is "chemical weathering" of common minerals in soils, subsoils, and groundwater systems followed by transport of the dissolved material to the oceans in continental drainage, where they are deposited on ocean floor. This sequence effects transfer of CO2 because mineral dissolution consumes CO2 containing acids, entrains bicarbonate, deposits carbonate minerals. CO2 in buried carbonate minerals returned to the atmosphere by volcanism and metamorphism. The relative rates of these processes determine the masses of CO2 in the atmosphere and lithosphere at any on time and, in the process, affect Earth's climate. It is therefore important the factors controlling the rates of the various processes in the cycle. Plant communities, are an important factor. Plants could enhance chemical weathering by raising subsurface concentrations of acids, facilitating the exposure of fresh mineral surfaces, and binding mineral grains into water-retaining structures characteristic of soils. The actual extent of weathering enhancement by these mechanisms is, however poorly understood because of the difficulty of factoring other variables out of comparative field studies. This study takes advantage of ongoing long-term, field-scale experiments in plant nutrient cycling. To collect needed data for subsequent research to test hypotheses on plant-weathering relationships. Existing instrumentation will is augmented to observe how chemical weathering evolves with depth and time in soils and subsoils beneath various plant communities