Effects of long-term elevated CO2 on earthworm populations, bioturbation and carbon sequestration in soils

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).One of the most pronounced global effects of human activity is the sharp increase in atmospheric carbon dioxide (CO2) concentration. Elevated atmospheric CO2 concentration has a direct impact on vegetation through increasing plant growth and an indirect impact through cascading effects on soil organisms that consume plant residues. Earthworms are considered one of the most important groups of soil organisms due to their substantial processing of plant material, incorporation and stabilization of plant-derived carbon in soils, and soil-mixing activities. Earthworm activities can affect carbon sequestration in soils by controlling the amount of carbon that is processed and by mixing the plant material deep in the soil, thereby influencing the amount of time that this plant-derived carbon remains in the soil. This project seeks to understand: (1) how plant responses to elevated CO2 have affected earthworm populations, (2) whether earthworm-mediated soil mixing has increased or decreased in forests exposed to elevated CO2, and (3) how these combined effects influence soil carbon sequestration. The investigators propose to combine geochemical techniques with ecological methodologies to make inferences about the role of earthworms on soil mixing and carbon sequestration. The study will be conducted in a temperate deciduous forest exposed to elevated CO2 since 1998 at Oak Ridge National Laboratory. To study the effects of elevated CO2 on earthworms, the densities and biomass of earthworm species in replicated forest plots exposed to elevated CO2 will be compared with those at ambient CO2 conditions . The investigators will use stable and radioactive isotopes as chemical markers and will measure biomarkers for specific plant components (i.e., leaves and roots) to identify separate mixing layers within the soil and to provide a more accurate knowledge of the fate of plant-derived carbon in these forest soils.The results from this project will contribute new knowledge about feedbacks and interactions among biological and soil processes that determine the degree of carbon sequestration in an ecosystem. Specifically this project will: (1) provide new information on cascading effects of elevated CO2 and global change on temperate forests, (2) quantify the role of earthworms on soil mixing and carbon sequestration, (3) apply a novel method using radioisotopes to study the effects of global change on soil processes, and (4) generate important functional data that will provide an unprecedented context for earthworm ecology in carbon cycling and global change research. An important outcome of this proposal will be the incorporation of earthworm research in on-going science education activities in high schools of Chicago public schools from districts that serve mostly underrepresented groups. In addition, funding for this project will broaden participation in science, and represent an employment opportunity for the PI, who is a beginning investigator, as well as for undergraduate students from the University of Illinois at Chicago who will participate in this research, providing them unique experiences in science with real-world implications.