Because of the rapidly increasing CO2 emissions, it is important to know how the earth can compensate for the elevated CO2 levels. Earlier experiments involving elevated CO2 levels determined that both storage (in organic plant matter) and respiration rates (in roots and microbes) of carbon increase with more CO2 present. The goal of the present research is to follow how microbial processing and mineral weathering in surface and shallow soils transform carbon fixed in temperate forests. By doing so, the way in which carbon fixing affects the groundwater carbon budget and watershed processing can be determined. To do this, soil is gathered from four main sites for analysis: stands of aspen and sugar maple, elevated CO2 chambers, and a nearby field. By contrasting results from the natural (aspen, sugar maple, field) vs. experimental (elevated CO2) sections, the comparison of carbon transformation paths and mechanisms is possible. The soil is then tested for release of minerals and gases using experimental weathering arrays (addition of organic acids), lysimeters, and gas wells. Initial results indicate that dilute, dissolved organic carbon-rich solutions prevalent in the upper 20 cm of soil eventually grade down to inorganic carbon and mineral solutions similar to groundwater composition at 4m. Likewise, the amount of dissolved organic carbon in soil waters is high (3-4 mM) in shallow samples and low (0.6 mM) in deeper soils. These results suggest that organic carbon fixed in the rooting zone is transformed to dissolved inorganic carbon via respiration and mineral solubilization coupling before reaching the groundwater table. Thus, the inorganic carbon levels will rise in groundwater, but organic levels should remain stable due to the fixation and transformation that occurs as water leaches through the soil.
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