CHANGES IN PLANT MEDIATED MINERAL WEATHERING UNDER ELEVATED CO2

Elevated concentrations of atmospheric CO₂ brought about by human activity creates changes in plant morphology, growth rate and exudate production. Our study sought to understand the effect of these changes on soil mineral weathering using plants grown under two conditions, Ambient CO₂ (400ppm) and elevated CO₂ (1000ppm). Plants were grown in flow-through microcosms consisting of a mixture of quartz and apatite sands. Plant growth was sustained by a nutrient solution devoid of Ca and P. Using AAS and colorimetry, Ca and P content of the leachate and plant tissue served as a proxy for apatite dissolution. Plants were harvested periodically during the 8-week experiment to show Ca and P content with time. Plants grown in elevated CO₂ had a greater root to shoot ratio. This outcome was expected based on the results of many other studies. The planted microcosms were found to have a lower pH than abiotic controls due to root respiration and exudation of organic acids. Because of this, 3.5 times as much Ca, by weight, was released in the first 6 weeks of the experiment. During the first 4 weeks of the study, plants grown in elevated CO₂ were also better able to release Ca and P from apatite than plants receiving the ambient treatment. While the rest of the data are still being collected, these results show the importance of below ground carbon fluxes in speeding mineral weathering.