Thesis Defense: 'Root and microbial respiration dominate CO2 efflux in an arctic ecosystem,' June 19

Tuesday, June 19, noon
ConocoPhillips Integrated Science Building, Room 120

The Biological Sciences Department is pleased to have Aliza Segal, graduate student in biological sciences, defending her thesis "Root and microbial respiration dominate CO2 efflux in an arctic ecosystem." The graduate committee will consist of Bjartmar Sveinbjornsson, Ph.D., Paddy Sullivan, Ph.D., Jeff Welker, Ph.D., and Kim Peterson, Ph.D.

Segal on her thesis:
"Ecosystem respiration (ER) is the largest carbon flux out of ecosystems, yet our ability to model this aggregate flux lags considerably behind our ability to model photosynthesis in arctic tussock tundra. Partitioning respiration into its component fluxes is a critical step towards understanding differential responses of respiration to climate change. To partition respiration into aboveground, belowground autotrophic and belowground heterotrophic respiration, I used a novel herbicide plant exclusion method, ecosystem-level biomass estimates, and tissue-scale respiration measurements of mosses, leaves and roots.

The most important drivers of variation for each constituent were identified at the species-level using multiple linear regression. My results suggest that belowground sources contribute substantially to ER. I found that, near the end of the growing season, 52 percent of ER was attributable to bulk soil microbial respiration and 24 percent to root respiration. Respiration of the leaves and roots of Eriophorum vaginatum contributed 6.5 to 20 percent of total ER over the course of the season, while mosses contributed between 3 and 8 percent. Our findings contrast with efforts to model ER as an aggregate flux, which often use only aboveground drivers to predict the flux. I hypothesize that these aboveground factors may be serving as proxies for unidentified belowground drivers."

Parking on campus is enforced during the summer semester. A parking pay station is located in the parking garage behind the Conoco Phillips Science Building. Please call the Department of Biological Sciences at (907) 786-4770 for further assistance.