User:Dawson Fairbanks

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Contact Info

Dawson Fairbanks

• Dawson Fairbanks
• University of Arizona
• Saguaro Hall 315
• Tucson, AZ
• dawsonfairbanks{at}email.arizona.edu

Education

• 2014-present, Ph.D Soil, Water, Environmental Science, University of Arizona
• 2012, B.S. Biological Sciences, Northern Arizona University

Research Interests

• Stable Isotope Analysis
• Environmental Microbiology
• Soil Science
• Global Change
• Ecosystem Ecology
• Landscape Evolution

About

I started out my research career assisting in Catherine Gehring's Mycorrhizal Ecology Lab at Northern Arizona University as an undergraduate research technician. I assisted in greenhouse, field, and laboratory research experiments studying how biotic and abiotic forces in the environment affect mycorrhizal populations and communities, and how these changes in turn influence host plant performance. In 2012, I received the Hooper Undergraduate Research Award for $3,500 to carry out my own independent research project to test the hypothesis that exotic Russian Olive could outcompete native Fremont Cottonwoods in soils impacted by Tamarisk based on the findings that Tamarisk had been shown to disrupt mycorrhizal mutualisms of native species Cottonwoods and Willows. I conducted a greenhouse study planting Cottonwood and Russian Olive seedlings in live and sterilized soil collected from a Tamarisk stand. I then analyzed root tips using clearing and staining techniques to quantify percent mycorrhizal colonization in both plant species and compared fungal colonization to relative growth and success of each plant species. Tamarisk was shown to increase potentially pathogenic fungal colonization in both plant species where Russian Olive seedlings exhibited a greater negative effect in terms of relative growth. These findings were presented at the May 2013 Hooper Undergraduate Research Award Symposium and the NAU Undergraduate Research Symposium.

During this time I also began working in Dr. Bruce Hungate's laboratory at NAU advised by Dr. Paul Dijkstra studying biochemical processes of soil and hot spring microbial communities using newly developed stable isotope techniques. From incubation experiments conducted on whole living soils, we were able to calculate the Carbon Use Efficiency using position-specific stable isotope pairs to calculate the central carbon metabolic network including glycolysis, TCA cycle, and pentose phosphate pathways. The metabolic model was solved using the ratio of CO₂ production from 1-¹³C and from U-¹³C glucose and from 1-¹³C and 2,3-¹³C pyruvate. To evaluate the model we incorporated additional isotopomers of glucose and the model then calculated the ratio of ¹³CO₂ production from the remaining C-atoms of glucose relative to U-¹³C glucose. These modeled values for glucose isotopomers were compared with measured glucose isotopomer ratios. By measuring the reaction rate at which ¹³CO₂ is released we calculated how much carbon is respired into the atmosphere vs. incorporated into microbial biomass and biosynthetic precursors. These findings were presented at the December 2012 AGU conference in San Francisco.

Now, I am continuing my research investigating C cycling in soils at the Critical Zone Observatories located in the Jemez River Basin in New Mexico and the Santa Catalina Mountains near Tucson. My dissertation project is largely interdisciplinary working with modelers, biogeochemists, hydrologists, and geologists with the goal of understanding the functional role of microorganisms and to identify physiological responses to soil in relation to changing environmental conditions and climates. To do this we will utilize a metadata-rich and model-supported systems context to examine all three domains of fungal, bacterial, and archaeal communities targeting changes in relative abundances of specific taxa or functional groups through a host of meta-omic (-genomic, -transcriptomic, and -proteomic) techniques and enzyme assay analysis to gain an overall understanding into functional processes underlying carbon storage and release and the role of disturbance in landscape evolution processes.

Current Projects

Microbiology in the Critical Zone: geomicrobiology, "hot spots and hot moments", and ecosystem services in the JRB-SCM CZO

The JRB-SCM Critical Zone Observatory is an interdisciplinary observatory that will improve our fundamental understanding of the function, structure and co-evolution of vegetation, soils, and landforms that comprise the Critical Zone (CZ). This CZO lead by Jon Chorover has developed a conceptual framework of (a) “hot spots and hot moments”, where landscape change occurs non-uniformly over space and time, for example occurring rapidly after major fire events (which our CZO just experienced in summer 2013), and (b) an energy/carbon flow equation ("EEMT", effective energy and mass transfer, developed by CZO PI Craig Rasmussen) that quantitatively describes critical zone landscape evolution. With the recent summer 2013 renewal the SWES-MEL lab and the Gallery Lab have begun to bridge microbiology and CZO biogeochemistry in the context of water and soil processes, including decomposition, weathering, carbon stabilization, and carbon flow, and water purification. Our approach spans both physiological (Gallery Lab) and meta-omic (Rich lab) approaches.

Presentations

• Fairbanks, Dawson, Erin Miller, Elena Salpas, Shannon Hagerty, Bruce Hungate, Jane Marks, George Koch, Egbert Schwartz, Scott Thomas, Brian Hedlund and Paul Dijkstra. Measuring and modeling activities of the central carbon metabolic processes using position-specific ¹³C-labeled metabolic tracers in soil and hot spring microbial communities. (2013). Poster presentation at the China-US Collaborative Research Symposium on Life in Terrestrial Geothermal Springs, June 26-28 in Kunming, China.

• Fairbanks, Dawson, Ashley Craig, Catherine Gehring. Alterations in soil microbial communities in Tamarisk impacted soil: effects on growth and establishment between exotic Russian olive and native Fremont Cottonwoods. (2013 ). Poster presentation at Northern Arizona University Undergraduate Research Symposium, Flagstaff, Arizona.

• Dijkstra, Paul, Kees-Jan van Groenigen, Shannon Hagerty, Elena Salpas, Dawson Fairbanks , Bruce Hungate, George Koch, Egbert Schwartz. Metabolic Flux Analysis of Microbial Communities in Soils, Litter, and Hot Spring Sediments. (2013 ). Oral Presentation at the 4^th Annual Argonne Soil Metagenomics Meeting, Chicago, Illinois.

• Dijkstra, Paul, Kees-Jan van Groenigen, Shannon Hagerty, Elena Salpas, Dawson Fairbanks, Bruce Hungate, George Koch, and Egbert Schwartz. Measuring and modeling C flux rates through the central carbon metabolic pathways in microbial communities using position-specific ¹³C-labeled tracers. (2012 ). Oral presentation at the American Geophysical Union December Meeting, San Francisco, California.

• Fairbanks, Dawson, Bruce Hungate, George Koch, Egbert Schwartz, Scott Thomas, Brian Hedlund and Paul Dijkstra. Evaluating metabolic models of intact soil microbial communities using position-specific ¹³C-labeled glucose. (2012). Poster presentation at the American Geophysical Union December Meeting, San Francisco, California.

Publications

• Dijkstra, Paul, Elena Salpas, Dawson Fairbanks, Erin Miller, Shannon Hagerty, Bruce Hungate, Jane Marks, George Koch and Egbert Schwartz. (In Prep). Evaluating and Comparing Metabolic Models for Soil Microbial Communities.

Awards

• 2014 Alfred P. Sloan Foundation Indigenous Graduate Partnership Fellowship, University of Arizona; $38,500
• 2014 UA Graduate Access Fellowship, University of Arizona; $10,000
• 2012 Hooper Undergraduate Research Awards, Northern Arizona University; $3,500