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@ucmerced.edu
Michael Vincent Rodriguez
Postdoc
Michael’s research focuses on the impact of sustainable agricultural and organic waste management practices on environmental quality and climate change. Michael earned his B.S. in Chemistry at UC Davis (2016) and Ph.D. in Environmental Science at UC Riverside (2023). Michael’s dissertation researched greenhouse gas and ammonia emissions from dairy manure management and manure land application. Michael was also a fellow for the UCOP Carbon Neutrality and Global Food Initiatives and researched bokashi fermentation and digestion by insect larvae as organic waste management strategies to foster soil health and reduce trace gas emissions. His current work collaborates with community organizations to research the potential, implementation, and impacts of community-scale composting in the San Joaquin Valley.
Shijana Duwadi
Postdoc
Shrijana Duwadi is from Gorkha, Nepal. She earned her Master’s in Forestry from Auburn University (2019) and Ph.D. in Environmental Science from Tennessee Technological University (2023). Her dissertation focused on the factors affecting nutrient retention recovery and greenhouse gas emissions in restored agricultural floodplain wetlands. Shrijana’s research interests include global change, soil ecology and biogeochemistry, plant-soil-microbe interactions, carbon sequestration, and ecological statistics. She believes in collaborative science and enjoys mentoring. Her current work investigates the effects of organic amendments on soil carbon stability and greenhouse gas dynamics in an effort to manage tradeoffs from California’s Landmark Methane Policy. Outside academia, Shrijana is a nature enthusiast with a passion for literature and fine arts.
Zach Malone
PhD Candidate (co-advised by Dr. Asmeret Asefaw Berhe)
Zach is a PhD candidate interested in soil climate solutions and closing the nutrient loop. He is specifically studying the use of organic matter amendments, such as compost, on urban turf grass soils to improve soil health and carbon storage. He is also interested in the impacts of compost on urban soil emissions, such as GHGS, and air pollutants such as ammonia and NOx. He also received his B.S. in Earth System Science from UC Merced where he worked as a Wilderness Education Ranger for Yosemite which influenced his interest in studying urban greenspaces.
Melinda Gonzales
PhD Candidate
Melinda is a PhD student interested in soil health practices in the Central Valley. She received her Bachelor’s in Agriculture studying soil science from CSU, Chico. She currently is studying biochar as a greenhouse gas-reducing amendment in dairy manure composting as well as its further implications on soil carbon sequestration and plant productivity.
Evelyn Perez-Agredano
Phd Student
Evelyn is a PhD student interested in researching regenerative agricultural practices and their potential to increase soil health and mitigate climate change. She is particularly interested in exploring the effects of organic soil amendments, like co-composting with biochar, on nutrient cycling, carbon sequestration, and GHG emissions in agroecosystems. Evelyn received her B.S. in Environmental Systems Science from UC Merced where she first joined the lab as an undergraduate researcher. As a grad student, she is studying the effects of soil health practices in California almond orchard systems.
Aaryn Wilson
Phd Student
Aaryn is a PhD student interested in food sovereignty, community-university partnerships, and innovative ways to compost food waste. He received a B.S. in plant science from the University of Minnesota. Before enrolling as a grad student, he served with AmeriCorps. He was a fellow in the inaugural ‘Equipping Next Gen Ag Leaders’ hosted by Green Lands Blue Waters.
Samuel Lee
Junior Specialist & Lab Manager
Samuel is a Junior Specialist interested in the effects of compost on urban soil emissions and health. He is focusing on experimental design, soil sampling, and field data collection of soil gas fluxes, soil conditions, and turf health in urban environments. He is also interested in various applications of biochar to increase carbon sequestration, reduce GHG emissions, and lower chemical fertilizer usage. Samuel received his B.S. in Environmental Systems Science from UC Merced where he collaborated and led a greenhouse biochar experiment as an undergraduate research assistant.
Whitman Ryals Bennett
Lab mascot & heavy machines operator
LAB ALUMNI
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
Alexia Cooper
PhD (2020-2024)
Alexia focuses on soil health, including compost amendments, fostering drought resilience, and climate mitigation through soil carbon sequestration. With diverse experience in urban and rural agricultural systems, her current research delves into the effects of soil health practices on orchard systems, emphasizing deep soil carbon and mycorrhizal fungi’s role in enhancing tree resilience to drought. Alexia holds a B.S. in Environmental Science (2017) from Westminster University and a Masters in Environmental Management (2020) from Western Colorado University.
Elena Bischak
PhD (2019-2023)
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 (2019-2023)
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.
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.
Bárbara Maressa dos Santos
Junior Specialist
Bárbara is a junior specialist passionate about soil health practices and regenerative agriculture. She is interested in exploring innovative approaches to sustainable farming and reversing climate change. She currently focuses on studying the effects of soil health practices in almond orchard systems in California. Bárbara holds a B.S. in Animal Science (2019) from São Paulo State University and a Masters in Plant and Soil Sciences (2023) from Oklahoma State University
Jocelyn Rojas
Junior Specialist (2023-2024)
Jocelyn is a first-generation college graduate with a B.S. in Environmental Systems Science from UC Merced. She is interested in community-engaged research at the intersection of environmental science and social justice. Her goal is to contribute to sustainable and equitable solutions to address issues related to industrial agriculture, climate change, and access to natural science education.
Ernesto Mendoza
Undergraduate Researcher (2024)
Ernesto Mendoza is a 4th year Environmental Systems Science undergraduate. His interest in soil health soils as a whole has only grown since starting at UC Merced. Working in the agroecology lab has inspired Ernesto to pursue a future in the field.
Alicia Corcuchia
Undergraduate Researcher (2024)
Alicia is an undergraduate student graduating in the spring of 2024 with a B.S. in Environmental Systems Science. She is interested in sustainable approaches to agriculture and climate change.
Josh Thomas
Undergraduate Researcher (2023)
Josh is a second-year bioengineering student interested in sustainability and material science. He assists the lab in soil carbon studies.
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.”
Taylor Cottrell
Undergraduate researcher (2020-2021)
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.
Chiara DeLeon
Undergraduate researcher, 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 researcher, UC Merced (2019)
Buraaq studies Mechanical Engineering at the University of California, Merced. He is interested in developing automation solutions for sustainability oriented labs.
Jillian Cristobal
Undergraduate researcher, 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.
Naomi Jun
Undergraduate researcher, 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.
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.
Mahealani Wilson
Undergraduate researcher, 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.
AGROECOLOGY LAB 