University of Hawai‘i at Manoa
Skip Breadcrumb

Last updated on Wednesday, August 16, 2017     Make updates ->

Rebecca  Ryals

Name :

Rebecca Ryals

Title :

Asst Prof

Unit :

Department of Natural Resources and Environmental Management

Address :

1910 East-West Road
                    Honolulu, HI 96822

Room :

Sherman Lab 220

Phone :


Fax :


E-mail :

Website :

Specialties :

Agriculture, ecosystem ecology, soil carbon and nitrogen cycling, greenhouse gas emissions, compost, grazing systems

Professional Prep/Appointments :

PhD, University of California, Berkeley (2012)
MEM, Duke University (2006)
BS, Marywood University (2004)

Projects :

Ecological-based sanitation
We are collaborating with Sustainable Organic Integrated Livelihoods (SOIL) in Haiti to improve approaches to composting human waste. The composting of human waste and its use as an agricultural soil amendment can tackle three important challenges - providing improved sanitation for vulnerable communities, reducing the spread of intestinal-borne pathogens, and returning nutrients and organic matter to agricultural soils. Our research seeks to quantify these benefits and potential trade-offs.

Managing tropical grazing systems for carbon sequestration and efficient nutrient cycling
Rangelands represent the largest land use globally and store a large portion of the world's soil carbon. Healthy functioning of soils is key to ecosystem health, rangeland productivity, and long-term profitability and sustainability of grazing lands. The management of rangelands directly impacts soil health, nutrient cycling, and carbon storage. However, ranchers often lack the necessary baseline information and decision support tools to develop effective carbon-farming plans. We are working with ranchers across the state to develop effective soil carbon monitoring plans and to do novel research to better understand controls on soil carbon storage. We are also conducting field research to test the impact of management practices on soil carbon and nutrient cycling.

Courses Taught:

NREM 460/TPSS 450: Sustainable Nutrient Management of Agroecosystems (4 credits; every other spring semester)

NREM 491/631: Sustainable Agriculture Seminar - Climate Change Solutions in Terrestrial Ecosystems (3 credits; fall semesters)

NREM 695: MEM Capstone Preparation (1 credit; every other year, fall and spring semesters)

NREM 696: MEM Capstone Experience (3 credits; every other year, fall and spring semesters)

Research Interests :

My lab studies how nutrients and carbon move into, within, and out of ecosystems. We are particularly interested in applying ecosystem science to research solutions to some of today's most challenging problems, including climate change, sanitation, nutrient pollution, and food production.

Publications :

Clark, S. R. Ryals, D. Miller, C. Mullen, D. Pan, M. Zondlo, A.A. Boateng, M.G. Hastings. 2017. Effluent gas flux characterization during pyrolysis of chicken manure. Submitted to ACS Sustainable Chemistry and Engineering. DOI: 10.1021/acssuschemeng.7b00815 

Tully, K., R. Ryals. 2017. Nutrient cycling in agroecosystems: Balancing food and environmental objectives. Submitted to Agroecology and Sustainable Food Systems 41:761-798. 

Castner, E., A. Leach, N. Leary, J. Baron, J. Compton, J.N. Galloway, M. Hastings, J. Kimiecik, J. Lantz-Trissel, E. de la Reguera, and R. Ryals. 2017. The Nitrogen Footprint Network: A multi-institution program to limit nitrogen pollution. Sustainability: the Journal of Record 10:79-88 

Hastings, M.G., R.T. Barnes, J. Berry, J. Kimiecik, R. Ryals, J. Lantz-Trissel. 2017. Calculating institutional nitrogen footprints creates connections across campus. Sustainability: the Journal of Record 10:74-78. 

Cayuela, M.L., E. Aguilera, A. Sanz-Cobena, D.C. Adams, D. Abalos, R. Ryals, W. Silver, L. Barton, M.A. Alfaro, V. Pappa, P. Smith, J. Garnier, G. Billen, A. Bondeau, L. Bouwman, L. Lassaletta. 2017. Nitrous oxide emission factors in Mediterranean climate cropping systems: a revision of the available literature and assessment of difference with official national estimates. Agriculture, Ecosystems and Ecology 238:25-35. 

Yang, W.H., R. Ryals, D. Cusack, W.L. Silver. 2017. Cross-biome assessment of gross soil nitrogen cycling in California ecosystems. Soil Biology & Biochemistry 107:144-155.

Rowntree, J.E., R. Ryals, M.S. DeLonge, W.R. Teague, M.B. Chiavegato, P. Byck, T. Wang, S. Xu. 2016. Potential mitigation of Midwest grass-finished beef production emissions with soil carbon sequestration. Future of Food: Journal on Food, Agriculture and Society. 4:31-38. 

Ryals, R., V. Eviner, C.E. Stein, W.L. Silver. 2016. Grassland compost amendments increase forage production without changing plant communities. Ecosphere. 7:e01270. 

Ryals, R., M. Hartmann, W.J. Parton, M.S. DeLonge, and W.L. Silver. 2015. Simulating soil carbon and greenhouse gas dynamics in grasslands amended with compost. Ecological Applications. 25:531-545. 

Ryals, R., M. Kaiser, M.S. Torn, A.A. Berhe, and W.L. Silver. 2014. Impacts of organic matter amendments on carbon and nitrogen dynamics in rangeland soils. Soil Biology and Biochemistry. 68: 52-61. 

DeLonge, M.S., R. Ryals, and W.L. Silver. 2013. A lifecycle model to evaluate carbon sequestration potential and greenhouse gas dynamics of managed grasslands. Ecosystems. 16: 963-979. 

Ryals, R. and W.L. Silver. 2013. Effects of organic matter amendments on net primary productivity and greenhouse gas emissions in annual grasslands. Ecological Applications 23:46-59. 

Ackerely, D.D., R. Ryals, W.K. Cornwell, S.R. Loarie, W.L. Silver, and T.E. Dawson. 2012. Potential impacts of climate change on biodiversity and ecosystem services in the San Francisco Bay Area. Chapter in Bay Area Climate Change Impacts Report, California Energy Commission. 

Silver, W.L., R. Ryals, and V.T. Eviner. 2010. Soil carbon storage in California rangelands. Rangeland Ecology and Management. DOI: 10.2111/REM-D-09-00106.1 

Lichter, J., S.A. Billings, S.E. Zegler, D. Gaindh, R. Ryals, A.C. Finzi, R.B. Jackson, E.A. Stemmlerm W.H. Schlesinger. 2008. Soil carbon sequestration in a pine forest after 9 years of atmospheric CO2 enrichment. Global Change Biology 14:2910-2922. 

Williams, E., N. Greenglass, and R. Ryals. 2007. Carbon capture, pipeline and storage: a viable option for North Carolina utilities? The Nicholas Institute for Environmental Policy Solutions and The Center on Global Change at Duke University. Working Paper. March 8, 2007.