Our Team

Rebecca Ryals

Associate Professor & Presidential Chair in Climate Change

My research program focuses on ecosystem-based climate solutions, particularly in agricultural and sanitation contexts. A major research theme is the capture, transformation, and beneficial reuse of organic wastes as resources to rebuild soil carbon and contribute to a more productive and just food system.

If you are interested in opportunities in the lab, email me at rryals[at]ucmerced.edu

Elena Bischak

PhD Candidate

Elena is a PhD student interested in nutrient recycling, soil carbon sequestration, and innovative sanitation solutions. She received a B.S. in biology from the College of William and Mary. Prior to enrolling as a grad student, she lived in Senegal for two years as a Peace Corps volunteer.

Brendan Harrison

PhD Candidate

Brendan is interested in researching climate solutions at the intersection of food and waste systems, nutrient cycling in agroecosystems, and climate justice. He received a B.S. in Earth Sciences and a B.A. in Environmental Studies from UC Santa Cruz. Brendan is studying the potential of biochar to reduce greenhouse gas and ammonia emissions during manure composting.  

Zach Malone

PhD student (co-advised by Dr. Asmeret Asefaw Berhe)

Zach is a PhD student interested in the use of organic matter amendments, such as compost, on urban soils to improve soil health and carbon storage. He received his B.S. in Earth System Science from UC Merced where he also worked as a Wilderness Education Ranger for Yosemite.

Alexia Cooper

PhD student

Alexia is interested in soil health practices, such as compost amendments, that foster increased drought resiliency, agricultural adaptation, and climate mitigation via soil carbon sequestration. She has worked in urban agricultural systems, perennial pasturelands, and now orchard systems. For her dissertation, she will be investigating the effects of integrative soil health practices on soil health parameters in orchard systems. In particular, she is intrigued by deep soil carbon dynamics, arbuscular mycorrhizal fungi and their ability to increase drought resiliency in trees. She is passionate about food sovereignty, environmental and racial justice, and indigenous land management practices. Alexia earned her B.S. in Environmental Science from Westminster College (2017), and a Masters in Environmental Management focused on Sustainable and Resilient Communities from Western Colorado University (2020).

Whitman Ryals Bennett

Lab mascot & heavy machines operator


Si Gao

Postdoc (co-advised by Dr. Asmeret Asefaw Berhe and Dr. Teamrat Ghezzehei)

Si joined the lab in June 2021 as a postdoc working on a collaborative project evaluating how organic amendments (manure compost, biochar, and co-compost) may influence soil C and N storage, microbial activity and functions, and greenhouse gas fluxes in dairy farm operations and agroecosystems in Central Valley, CA. Si holds a PhD in Forest & Conservation Sciences from the University of Montana, Missoula, and a MS in Environmental & Forest Sciences from the University of Washington, Seattle. Si has broad research interests in sustainable forest and agricultural management practices on soil health, fire disturbance on ecosystem C and nutrient cycling, and the functions of pyrogenic organic matter in soil microbial N and P cycling. Si is now an Assistant Professor at California State University, Sacramento. Visit Si’s personal website: https://gaosi.weebly.com/

Gavin McNicol

Postdoc (2016-2017)

Gavin was a postdoctoral fellow in the Ryals Lab after receiving my PhD in Ecosystem Science from UC Berkeley. As a postdoc, he collaborated with the non-profit Sustainable Organic Integrated Livelihoods (SOIL) that tackles pressing sanitation and soil fertility issues in Haiti. His work focused on understanding nutrient and greenhouse gas dynamics during the composting of human solid waste (EcoSan). His goal was to study EcoSan composting using the principles and methods of ecosystem ecology, to best support sustainable agriculture in Haiti. He is now a Assistant Professor at the University of Illinois, Chicago. Visit Gavin’s website

Yocelyn Villa

PhD (2018-2021)

Yocelyn’s research interests include: sustainable management practices in agroecosystems, soil quality and health, and carbon sequestration. She received her B.S. in Environmental Science from the University of California, Riverside. Her completed her Ph.D. on the effects of long-term application of biosolids in California rangelands effects carbon dynamics in soils in 2021. Yocelyn is currently the Soil Program Manager at Epic Cleantech.

Nick Krueger

PhD, UH Mānoa (2016-2021)

Nick’s research interests include tropical grazing systems and management, forage production and soil-plant-animal relationships. He received a B.S. in Agriculture from the University of Hawaii at Hilo and a M.S. in Agronomy from the University of Florida. He is now an instructor at UH Hilo.

Steven Heisey

MS, UH Mānoa (2017-2019)

Steven joined the master’s program at UH Manoa, after two years of service in the Peace Corps in Madagascar. He is interested in sustainable agricultural management, and his thesis explores the role of soil microbes in nutrient cycling and crop production. He is now a soil health specialist at USDA NRCS on Kauai.

Wailea Collins

MS, UH Mānoa (2015-2017, co-advised by Dr. Creighton Litton)

Wailea is interested in Hawaiian montane restoration ecology with particular interest in the role of community structure in resisting biological invasion. For her thesis, she investigated the effect of koa density on understory development; native outplant survival and non-native grass suppression in a restoration context. Wailea is originally from Maui island and received her B.S. in Wildlife Ecology at the University of Nevada, Reno. She is now employed as a forest ecologist technician on a collaborative project between the USDA, Colorado State University, and UH Hilo.

Chiara DeLeon

Undergraduate, UC Merced (2018-2020)

Chiara de Leon is studying chemistry with a biological emphasis. In the Ryals Lab, she contributed to several projects focused on quantifying soil carbon in agroecosystems.

Buraaq Alrawai

Undergraduate, UC Merced (2019)

Buraaq studies Mechanical Engineering at the University of California, Merced. He is interested in developing automation solutions for sustainability oriented labs.

Kate Porterfield

Undergraduate summer intern (2017 UH Mānoa, 2018, UC Merced)

Kate’s research interests include nutrient cycling and the use of novel soil amendments such as biochar in agroecosystems to reduce nutrient pollution and enhance food production. She graduatetd from Middlebury College with a degree in Conservation Biology. She is now a PhD student at the University of Vermont.

Jillian Cristobal

Undergraduate, UH Mānoa (2016-2018)

Jillian earned her undergraduate degrees in Natural Resource and Environment Management and Geography at the University of Hawaii at Manoa. She was a UH Nitrogen Footprint Fellow and conducted the university’s first Nitrogen Footprint.

Mahealani Wilson

Undergraduate, UH Mānoa (2016-2018)

Mahealani earned her undergraduate degree in Anthropology with a minor in Tropical Plant and Soil Science. She was a UH Nitrogen Footprint Fellow and conducted the university’s first Nitrogen Footprint.

Naomi Jun

Undergraduate, UH Mānoa (2017-2018)

Naomi was an interdisciplinary studies major with a keen interest in sustainable community planning. She assisted in the lab and in the greenhouse on all our projects related to soil science and sustainability.

Melisa Quintana

Undergraduate researcher (2020-2022)

Melisa was an undergraduate student in the school of Natural Science majoring in Earth Systems of Science with a minor in Natural Science Education. Before joining the lab, she was a Garden Assistant in her local community garden. Her interests include soil health, agriculture, conservation & regeneration of biodiversity, and nutrient cycling in natural ecosystems. “Joining the lab has expanded my knowledge in the application of soil health practices while also showing me that I have a place in STEM as a first generation BIPOC Scientist.”

Eddie Phosalath

Undergraduate researcher (2019-2022)

Eddie was an undergraduate in the School of Natural Sciences at UC Merced with a major in Biological Sciences with an Ecology and Evolutionary Biology emphasis. Choosing this path as it’s my passion to learn how we can solve our world’s environmental problems. In the past couple years, he has been involved in many environmental programs, including the Yosemite Leadership Program at UC Merced, Carson House, and an WildLink alumni.

Taylor Cottrell

Undergraduate researcher (2020-2021)