Because it grows rapidly and can develop high wood density, there’s increasing interest in the South for growing Eucalyptus commercially as a bioenergy feedstock. For the South, this means finding and testing Eucalyptus species that will grow in temperate areas as well as genetically modified hybrids bred to be frost tolerant. Growing well under a variety of conditions is part of Eucalyptus attraction, but it also raises questions about its potential to become invasive. Other major concerns include potential fire risk and water use.
To address these questions and more, the U.S. Forest Service and partners held a conference in 2012 in Charleston, South Carolina, to review the history of Eucalyptus research and growing culture and to look more closely at potential environmental issues that might arise as the plants introduction into the South expands. Sponsors of the conference included the National Council for Air and Stream Improvement (NCASI), ArborGen, MeadWestvaco, and the Forest Service.
Papers from the conference form a special issue of the International Journal of Forestry Research edited by Forest Service Southern Research Station (SRS) senior scientist John Stanturf and colleagues, Eric D. Vance, Thomas R. Fox, and Matias Kirst. “Environmental issues addressed in these papers include invasiveness potential, fire risk, water use, and sustainability,” says Stanturf. “The special issue also includes articles on Eucalyptus culture from other countries that can serve as a strong basis for hypotheses about environmental issues associated with growing this genus in the southern United States.”
SRS scientists were lead authors on articles about invasiveness and fire risk. For the article on the potential for invasiveness, Mac Callaham, research ecologist at the SRS Center for Disturbance Science, with co-authors Stanturf, SRS research ecologist Joe OBrien, and others, evaluated invasiveness by analyzing seedlings found within or near established Eucalyptus plantations on 19 sites, three in South Carolina and 16 in Florida.
The researchers found that some Eucalyptus species naturalize—spontaneously reproduce in their range—but there was no evidence for invasion (defined as spreading over long distances in large numbers.) “The intensively managed land use around the sites we looked at seemed to militate against escape,” says Callaham. “We found no seedlings in agricultural, suburban, or citrus orchard areas.” Overall, the papers in the special issue showed limited potential for invasiveness for most Eucalyptus species under consideration for wider planting in the South, though the authors caution that this might change as the scale of plantings increases.
In an article on fire risk, Scott Goodrick, project leader of the SRS Center for Forest Disturbance Science, and co-author Stanturf sought to answer questions about the potential fire risk of widespread plantings of Eucalyptus in the southern Lower Coastal Plain and how fires in Eucalyptus stands might differ from those in pine plantations. “Based on fuels modeling, we found that fire behavior in Eucalyptus plantations is not much different from that in pine plantations,” says Goodrick. “Stands managed on less than 10-year cycles will avoid the bark shedding that leads to fire problems. That said, fire risk will vary with the landscape Eucalyptus plantations are grown in. We recommend that future research focus on possible fire risk at the landscape level.”
To read an overview of other issues such as water use and sustainability, read the introductory article by Stanturf and fellow journal issue co-editors.
For more information, email John Stanturf at firstname.lastname@example.org