The Filley Biogeochemistry Research Group

Group members

undergraduate students

We offer a variety of undergraduate research experiences from the lab to the field. Please email Prof Filley ( with your questions and research interests.

graduate students

We are always looking for interested graduate students join the group. Please email Prof. Filley ( for more information.

postdoctoral scholars

We are currently searching for a postdoctoral scholar with expertise in greenhouse gas monitoring.

Meet the Group

Prof. Tim Filley
Dr. Tim Filley is professor in the College of Atmospheric and Geographic Sciences and the School of Geosciences at the University of Oklahoma (OU). Filley joined OU in 2021 and serves as the executive director of the Institute for Resilient Environmental and Energy Systems (IREES). Filley developed and directs the OU Stable Isotope Measurement facility, a core analytical facility within the Office of the Vice President for Research and Partnerships. Filley received his Ph.D. in geosciences from the Pennsylvania State University and he completed a post-doctoral fellowship at the Carnegie Science Earth and Planets Laboratory in Washington, D.C. He was a professor at Purdue University from 2000 to 2021, and served as director of the Purdue Center for the Environment from 2017 to 2021.
Dr. Jani Sparks
Dr. Jani Sparks is the lab manager for hte Filley Biogeochemistry Research Group, and a stable isotope specialist for the OU Stable Isotope Measurement Facility. She graduated from the University of Cincinnati’s Geology Department in 2017 with a focus on stable isotope biogeochemistry. During her time at UC, she focused on carbon, nitrogen, and sulfur isotope values in the terrestrial biological systems of Trinidad and Southwest Ohio. Prior to this, she gained a Master’s in Anthropology also from UC and a Bachelor’s in Interdisciplinary Studies from Miami University.
Dr. Martha Jimenez-Castaneda
Dr. Martha Jimenez-Castaneda is a postdoctoral research associate at the University of Oklahoma. Her research interests include biomarker analysis to study the pathways and preservation of organic matter. Martha is currently collaborating on diverse projects that evaluate carbon transformation, nutrient cycling, and soil health. She holds a M.Sc. in Natural Resources Management from The National Polytechnic Institute (Mexico) and earned her Ph.D. in Environmental Biogeochemistry from The University of Manchester (United Kingdom).
Dr. Carmen Roman
Carmen Roman is a postdoctoral research associate at the University of Oklahoma. She earned her PhD in Soil Science from the University of Alberta. She is the Project Coordinator of the PERU-Hub project, a multi-institutional initiative funded by USAID. Her research goals within the PERU-Hub project are focused on advancing sustainable and profitable crop production in the San Martin region of Peru. During her doctoral program, her research centered on the effects on greenhouse emissions and nitrogen dynamics from land application of biosolids to croplands.
Gordon MacLeod
Gordon is a Ph.D. candidate in biogeochemistry at Purdue University. His research examines the impact of invasive arthropod activity on factors affecting soil health, such as structure, carbon and nitrogen dynamics/transformations, and microbial activity. Other areas of interest are soil organic matter decomposition modelling, macrobiological effects on water quality, and GIS. He holds a B.S. in Chemistry from Salem State University and a B.A. in Music from Gordon College.
Ian Frantal
Ian Frantal is currently pursuing his M.S. in biogeochemistry at Purdue University in West, Lafayette IN, while completing his degree at the University of Oklahoma in Norman, OK. On a broad scale, Ian is interested in how land management and edaphic properties control soil’s response to rainfall events and drought. Using oven dried samples, he has analyzed soils from restored prairie and agricultural sites using an EA-IRMS, determining the %C and 13C makeup of both the near-surface and deep soil horizons. Additionally, he has used CO2 and O2 sensors to investigate how gas concentrations differ with changes in management, time, temperature, and soil moisture.
Taylor Frentz
Taylor is an M.S. student in the Department of Geography and Environmental Sustainability at the University of Oklahoma. She graduated from Oklahoma State University with a double major in Environmental Science and Soil Science and a minor in American Sign Language. Her current research explores the potential impacts agricultural tiles have on greenhouse gas emissions in the United States.
CJ McLemore
CJ McLemore is pursuing his M.S. in Geography and Environmental Sustainability at the University of Oklahoma. CJ graduated from Oklahoma State University with a B.S. in Environmental Science with a minor in Soil Science. Research interests include Traditional Ecological Knowledge (TEK), indigenous sustainability, and soil health. His current research focus is looking at how indigenous communities define soil quality/health and how their definitions relate to western soil science.
Prof. Nana Wu
Dr. Nana Wu is a Visiting Scholar in the Filley lab at the University of Oklahoma. She is an Associate Professor at Shenyang Jianzhu University, having completed her doctorate as a joint Ph.D. of Chinese Academy of Sciences and Purdue University. She has participated in 30 research projects and published 18 papers. Dr. Wu's research interests include terrestrial and Aquatic biogeochemistry, organic geochemistry, mechanisms and technology for water pollution control and treatment. Her current research focus is on turnover dynamics of lignin and substituted fatty acids in soil organic carbon.
Luke Christensen
Luke Christensen is an undergraduate at the University of Oklahoma in the College of Atmospheric and Geographic Sciences. He is pursuing a B.A. in Environmental Sustainability, with a concentration in science and natural resources as well as a minor in Geographic Information Systems (GIS) and Military Science. Academic interests include sustainability and resource management, the use of remote sensing in the study of wildlife populations, as well as other GIS applications in the field of natural resource management. As a research assistant for IREES, he has learned basic functions and operation of a Sercon EA-IRMS and aids in various other lab duties. LinkedIn:
Jordan Jones
Jordan Jones is a Pre-medical, Microbiology Student at University of Oklahoma. His research interest lies in the environmental effects on population health. Jordan is currently involved in research regarding soil respiration and the effect of storage and transport on Gas sample integrity.
Bailey Williams
Bailey Williams is an undergraduate student at the University of Oklahoma. She is pursuing a B.S. in Environmental Sustainability, with a concentration in natural resources and science, as well as a minor in GIS (Geographic Information Systems). Her academic interests include learning more about math, statistics, various software applications, and sustainability. During her time as a research assistant for IREES, she has learned about EA-IRMS and conducts multiple lab analyses.
Drew Baldwin
Drew Baldwin is a visiting undergraduate student at the University of Oklahoma. He is pursuing a B.S. in Geology & Geophysics at Purdue University. His academic interests include stable isotope geochemistry, dissolved organic carbon, structural geology, and data science. As a research assistant for IREES, Drew is focusing on dissolved organic carbon analysis and the effects of anthropogenic land cover change on carbon cycles in intensely managed landscapes.