Forest ThreatNet

University Partnership Focuses on Water and Carbon Use

By Stephanie Worley Firley, EFETAC

Climate change issues, including altered patterns of precipitation and runoff, will pose great challenges to resource managers in the future. It is no surprise, then, that climate change and water are two key research areas for a partnership effort between EFETAC’s Southern Global Change Program (SGCP) and North Carolina State University (NCSU).

Collaborative efforts by the SGCP research team and NCSU faculty John King, Asko Noormets, and Jean-Christophe Domec, from the Department of Forestry and Environmental Resources, focus on quantifying ecosystem-level exchanges of carbon and water as a function of stand age and climate in managed forests along the Lower Coastal Plain of North Carolina. Since 2004, researchers have been gathering data from loblolly pine plantations in which instrumented towers are continuously recording atmospheric carbon and water fluxes at the landscape scale using state-of-the-art technology known as the eddy covariance method. They are also monitoring sapflow sensors on individual trees that measure water use.

Above: SGCP biological scientist Michael Gavazzi trains a graduate student at the eddy flux measurement site. (Photo by Ge Sun)

“The project’s simple objectives are to quantify how much carbon dioxide plantations can absorb as well as how much water they use, and to provide new data to develop strategies to mitigate elevated atmospheric greenhouse gas concentrations through reforestation,” says Ge Sun, SGCP research hydrologist. “We are also analyzing how nutrient cycling and carbon balances are affected when human activities like forest conversion and ditching (draining wetlands) change the hydrology of a site and the associated ecological processes.”

According to Noormets, the data accumulated so far show that pine forests older than 14 years function as a large carbon sink, while recently planted pine plantations remain a strong carbon source through the first six years after planting. “In other words, older forests sequester (store) large amounts of carbon that would otherwise be present in the atmosphere,” explains Noormets. “We have also observed that a 15-year-old pine plantation with a closed canopy uses—and loses—more water than a recently planted site. Annual climatic variability and recent severe drought in 2007 have led to the initiation of other studies to examine how changes in precipitation may affect carbon storage in drained ecosystems.”

Above right: NCSU faculty Asko Noormets and Jean-Christophe Domec install sapflow sensors at the research site. (Photo by Michael Gavazzi)

This project continues a previous 5-year collaboration with Jiquan Chen from the University of Toledo. In working with Chen through the U.S.-China Carbon Consortium (USCCC), chaired by SGCP team leader Steve McNulty, SGCP scientists have joined forces with a wide range of institutions in China, including Beijing Forestry University, Chinese Academy of Sciences, and the Institute of Botany of the Chinese Academy of Sciences. Now, because of the NCSU collaboration, the research scope is still expanding. The U.S. Department of Energy recently awarded King and Noormets a grant to add a new flux measurement site in the Alligator River National Wildlife Refuge to understand wetland carbon sequestration and water cycles across a hydrologic gradient in eastern North Carolina. “Our study that focuses on coastal wetland ecosystems is rather unique in the U.S. and promises to fill some of the knowledge gaps identified by the global change community. The work will be able to generate policy relevant findings in the next few years,” says King.

Additionally, this carbon and water research has received much attention from the AmeriFlux and FluxNet communities that conduct similar studies around the world. “Data generated from the AmeriFlux and FluxNet sites contribute to continental and global synthesis on the impacts of climate change and management on carbon sequestration and water resources,” says Sun. McNulty adds, “Research on global change issues requires a wide range of close global collaborations. Forest Service research benefits tremendously from the long-term collaborative work with NCSU. We value the opportunities to work with NCSU and welcome participation of other institutions on this project.”

Above: A 70-ft. tower built in 2004 was instrumented to continuously measure carbon and water fluxes in a 15-year-old loblolly pine plantation on the coastal plain of eastern North Carolina. (Photo by Ge Sun)

For more information, contact Dr. Ge Sun at ge.sun@usda.gov or Dr. John King at John_King@ncsu.edu. To learn more about the U.S.-China Carbon Consortium, visit http://www.research.eeescience.utoledo.edu/lees/research/usccc/.