Dr. Vanessa Buzzard | Senior Research Specialist

Dr. Buzzard is a senior research specialist with Dr. Meredith in the School of Natural Resources and the Environment. She received her Ph.D. from the University of Arizona in the Department of Ecology and Evolutionary Biology in 2017, where she focused on plant functional trait distributions across both space and time. She has since moved from studies of predominantly natural systems to focus on urban environments, where she extends questions regarding the drivers of biodiversity and ecosystem function to the effects of green infrastructure water management on soils in urban environments. Her research aims to quantify shifts in physical, chemical, and biological soil health indicators in response to green stormwater infrastructure in the City of Tucson.

Dr. Gemma Purser | Postdoc, NSF

Gemma is a Postdoctoral Researcher in the Meredith Lab working on the NSF Signals in the Soils project in collaboration with Aerodyne Research, Inc. and QuantAQ. Her current research  focuses on understanding the transport and fate of volatile organic compounds (VOCs) in subsurface environments. Originally from the UK, Gemma has a BSC in chemistry and biology (University of Derby) and an MSc in analytical chemistry (Loughborough University). She obtained her PhD from The University of Edinburgh, where she conducted field-based emission measurements of VOCs from bioenergy forests and assessed their air quality impacts using an atmospheric chemistry transport model (EMEP4UK) in collaboration with UK Centre for Ecology & Hydrology and Forest Research.

Her interdisciplinary approach emphasizes studying processes from a whole ecosystem perspective, particularly exploring VOC dynamics across different scales, from biosphere-atmosphere to plant-microbe interactions. With a background in geochemistry and prior work on carbon capture and storage for the British Geological Survey, Gemma is interested in the broader implications of climate change mitigation strategies like bioenergy, afforestation, and urban greening. Her recently awarded BIO5 postdoctoral fellowship focuses on VOC deposition to urban forest soil’s and their role in mitigating atmospheric VOC (anthropogenic and biogenic) concentrations, with a future aim to link this to both air quality and soil health impacts (in collaboration with researchers from Boston University and Aerodyne Research Inc). 

Dr. Ian, Zhaoxin Zhang | Postdoc, DOE-GSP

Ian, Zhaoxin Zhang, is a Postdoctoral Researcher in Meredith lab where he mainly focuses on how trace VOCs, produced by microbial, plant, and abiotic processes, enhance soil carbon storage. He received a Bachelor degree in Environmental Science from Zhejiang University, China, where he discovered his interest in the domain of microbial remediation on VOCs and pursued further interdisciplinary study. Dr. Zhang received his PhD in 2023 from the Hong Kong University of Science and Technology where his dissertation centered on the Allelopathic Potential of Microbial Volatile Emissions on Suppressing Malodor at Victoria Harbor.

After graduation, he would like to devote his energy to explore more globally from solving regionally environmental issues in Hong Kong to conclude and answer the internal principles of biogenic VOCs on soil carbon cycling. Now, he is conducting field and lab experiments to determine how plant productivity, root biomass, and plant growth stages influence soil carbon through VOCs-mediated processes in an agroecosystem of the bioenergy crop sorghum at the Maricopa Agricultural Center and contribute to field work at the Blodgett Forest Research Station in the Berkeley Lab to help determine the impact of deep soil warming on soil carbon in the coniferous forest. He works on integration of multi-omics datasets including volatilomics, metagenomics, proteomics and machine learning to help understand how BVOCs impact soil.

S. Marshall Ledford | PhD Student, Genetics

Marshall is a doctoral student in the Genetics Graduate Interdisciplinary Program and a University Fellow. Originally from the Appalachian Mountains in North Georgia, he graduated from Vassar College with a B.A. in general biology. There, his research focused on analyzing post-translational modifiers in response to heat stress within a model moss species. Through experience working with NASA Ames, the Mars Society, and the American Society for Gravitational and Space Research, he has developed a strong passion for space research and astrobiology. In the Meredith lab, he is currently exploring the possibility of using soil gas fluxes as a method for life detection, with an emphasis on understanding the influence of environmental factors on microbial-gas interactions. Eventually, he hopes to incorporate how these might relate to biosignatures in extreme soil environments on Earth and elsewhere.

Parker Geffre | Research Technician I

Parker, a Tempe native, is a UA graduate with degrees in Biochemistry and Molecular Cellular Biology. As a research technician at the Meredith Lab, she currently works on VOC data analysis and synthesis, novel sensor testing, and various support roles depending on the project. Her research interests are at a crossroads of molecular biology and atmospheric chemistry. Parker focuses on linking VOC soil-atmosphere flux to microbial soil community composition and respective shifts through isotopic substrate labeling and low-cost VOC sensor development. Her primary project is focused on understanding the drought tolerance of soil microbes capable of degrading isoprene, the most abundant biogenic VOC on earth.

In her time at the Meredith Lab, she has worked directly with industry and international collaborators, specifically at Aerodyne Research, Inc. in Boston, MA and the Earth and Life Systems Alliance in Norwich, UK. Through her research, she seeks to help fill in knowledge gaps regarding the fate of VOC carbon. Parker also works to address the lack of accessible soil VOC data by compiling results from various studies to generate an open-access soil VOC database. Outside of research, Parker enjoys adventuring, studying British history, videogames, and drawing.