Lab Members

Rebecca Ryals (PI)


I am an Assistant Professor in the School of Natural Sciences’ Life and Environmental Sciences Unit at the University of California, Merced.

If you are interested in opportunities in lab, please contact me at rryals[at]

Ryals CV November 2017






Nicholas Krueger (Ph.D. student)


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






Steven Heisey (M.S. student, co-advised by Dr. Nhu Nguyen)

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Steven joining the master’s program at UH Manoa in 2017, 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.




Kate Porterfield (Undergraduate student)

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Kate joined the Ryals Lab as a research intern in the summer of 2017. Her 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. Kate is in her third year at Middlebury College where she is majoring in Conservation Biology. While she is now back in Vermont, she continues to work with the Ryals lab for her undergraduate research project, which consists of measuring soil carbon pools across a chronosequence of rangelands with different timescales of grazing management.



Mahealani Wilson (Undergraduate student; UH Nitrogen Footprint Fellow)

Aloha! My name is Mahealani and I am a current junior majoring in anthropology with a minor in Tropical plant and Soil Science. I am currently working on calculating and reducing reactive nitrogen emissions on UH Mānoa’s campus.







Jillian Cristobal (Undergraduate student; UH Nitrogen Footprint Fellow)

JilianJillian is a third year student at the University of Hawaii at Manoa and majoring in Natural Resource and Environment Management as well as Geography. She is currently working on calculating UH Manoa’s Nitrogen Footprint as a method to assess and track sustainability practices and goals at the institutional level.







Lab Alumni

Wailea Collins (M.S. 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.





Gavin McNicol (Postdoctoral Fellow, 2016-2017)


Gavin was a postdoctoral fellow in the Ryals Lab at UH Manoa from 2016 – 2017 after receiving my PhD in Ecosystem Science from UC Berkeley. He is now a postdoc at the University of Alaska. While at UH, 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. To borrow from Paul Farmer (co-founder of Partners in Health), we are especially excited by the science and impact that can be effected when we start thinking about about ecology ‘in the broadest possible sense’.

Gavin’s website




Naomi Jun (Undergraduate student)

Naomi is an interdisciplinary studies major with a keen interest in sustainable community planning. She has been working in the lab since summer 2017. She assists in the lab and in the greenhouse on all our on-going projects.