An owl at rest on a remnant fence from the days this soybean field was a pasture, Rondônia, Brazil. Photo credit: Gillian Galford.

Ecosystems Center Scientists Active in Nitrogen 2007 Conference

Ecosystems Center director Jerry Melillo and MBL adjunct and visiting scientists Robert Howarth and James Galloway helped to organize the N2007 symposium, held October 1-5 in Costa do Sauipe, Brazil. The symposium addressed the impacts and inequities of nitrogen use on Earth. Associate scientist Christopher Neill attended, along with two alumni of the center’s Semester in Environmental Science, Toby Ahrens and Eve-Lyn Hinckley, both doctoral candidates at Stanford University.

The last 40 years have seen an extraordinary change in the global nitrogen cycle. As recently as the 1960s, nitrogen availability on Earth was controlled by natural processes, but the production of synthetic nitrogen fertilizer and the release of nitrogen from fossil-fuel combustion now match the natural supply of reactive nitrogen on the planet. The use of nitrogen is imbalanced: industrialized countries suffer pollution problems from too much nitrogen and low-income countries have a shortage of nitrogen that constrains food production. The meeting brought together some of the world’s best nitrogen scientists and development experts from 42 countries.

	Dryland rice between rainstorms, Mato Grosso, Brazil. Photo credit: Gillian Galford.

Toby Ahrens presented a talk and a poster on his Ph.D. research projects from his Stanford University. The talk was titled, “Understanding controls on regional nitrogen-use efficiency with achievement distribution curves,” and the poster, “A comparison of four methods used to determine clay-fixed ammonium in soils and implications for simulated crop growth and N cycling.” Mr. Ahrens received his master's degree in environmental engineering from Stanford in 2004 and is currently working on his PhD dissertation in Dr. Pamela Matson's biogeochemistry laboratory. His dissertation is organized around understanding the controls on nitrogen-use efficiency in agro-ecosystems. Projects have included the effects of regional variability in climate on crop growth and nitrogen cycling, soil nitrogen retention mechanisms and feedbacks to fertilizer nitrogen fates, and regional simulation modeling to understand what factors lead to nitrogen-use efficiency underachievement in farmers’ fields.

Ms. Hinckley also studies with Pamela Matson in Stanford’s Ph.D. program. Her research looks at how different near-surface hydrological flow paths affect the fate and transport of applied sulfur in Northern California vineyards. According to Ms. Hinckley, her interest in working at the interface of hydrology and biogeochemistry began at the Ecosystems Center, when she worked with Chris Neill on his Martha's Vineyard groundwater nitrogen project.

Also attending the conference were Gillian Galford, a graduate student in the Brown/MBL Graduate Program in Biological and Environmental Sciences, and Joaquin Chaves, a postdoctoral associate at Brown.