Date of Award

Spring 5-13-2017

Level of Access Assigned by Author

Open-Access Thesis



Degree Name

Master of Science (MS)


Earth Sciences


Amanda Olsen

Second Committee Member

Aria Amirbahman

Third Committee Member

Stephanie Burnett


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). Phaseolus vulgaris (common beans) 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 calcium (Ca) and phosphorous (P). Using Atomic Adsorption Spectroscopy 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. P. vulgaris 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, nutrient uptake and exudation of organic acids. Because of this, as much as 811% more Ca was released from biotic than abiotic experiments by the end of week 8. The presence of plants resulted in the release of over 100´ more P compared to their absence. Plants grown in elevated CO2 released 82% more Ca and 80% more P than those grown in ambient conditions. Although elevated CO2 helped plants to grow larger root structures and lower the solution pH, no significant change to weathering rates was observed during the experiment. Our results show the importance of below ground carbon fluxes in creating changes to the rhizosphere which aid in P release from apatite.