David Gorchov, professor of botany, and Mary Henry, assistant professor of geography at Miami University, have been awarded a U.S. Department of Agriculture National Research Initiative (NRI) grant. The $376,940 grant will support their research on how landscape patterns shape the invasion dynamics of the non-native shrub Amur honeysuckle (Lonicera maackii). Their work involves an innovative use of remote sensing approaches to determine the historical spread of the shrub.
Invasive species such as honeysuckle threaten biodiversity, habitat quality and ecosystem function, according to the U.S. Department of Agriculture (USDA). It is estimated that 50,000 species of plants and animals have been introduced into the U.S. resulting in more than $100 billion in losses and damage each year. Invasive species have contributed to the decline of 42 percent of the endangered and threatened species in the U.S., estimates the USDA.
Gorchov, Henry and colleague Oscar Rocha, assistant professor of biological science at Kent State University, will research this problem in our own backyard. Amur honeysuckle was introduced to North America from China as an ornamental shrub in the late 19th century; it was widely planted in the eastern U.S. but escaped from cultivation and is now naturalized in at least 24 states. It was first reported naturalized in Ohio in 1961 in Hamilton county, and is now naturalized in 34 other counties in Ohio. It is "by far the commonest shrub, native or alien, in Greater Cincinnati," says Gorchov.
Seeds of this shrub are spread by some of the many bird species that eat the fruits, with robins and starlings most important in southwest Ohio, according to research by Gorchov's former doctoral student Anne Bartuszevige. It competes with tree seedlings, wildflowers and other native plants and is considered a serious problem in eastern and Midwestern forests.
Gorchov, Henry and Rocha will determine how landscape patterns, such as forest fragmentation, shape the pattern and rate of invasion of Amur honeysuckle.
Their first objective is to document the historical expansion of Amur honeysuckle over the last 20 years in southwestern Ohio. Based on a successful pilot study, they will use Landsat satellite images to detect the historical spread of the shrub. Because Amur honeysuckle is the first shrub to leaf out in spring and the last to drop its leaves in autumn, invaded stands can be distinguished with satellite images, says Henry.
Their study "Detecting an invasive shrub in a deciduous forest understory using late-fall Landsat sensor imagery," published in the August 20, 2007 issue of the International Journal of Remote Sensing, was the first to use distinct leaf phenology (seasonal changes in plant growth) to remotely sense an understory species, according to Henry and Gorchov. (Students involved in the Miami's National Science Foundation-funded Research Experience for Undergraduates program on Research in Human-Dominated Landscapes contributed to this pilot study).
Research supported by the new grant, conducted by master's student Bryan Wilfong (Institute of Environmental Sciences) has improved the detection ability, enabling the scientists to distinguish heavily invaded from lightly invaded stands.
Once they have reconstructed the historical invasion, the researchers will develop a model to predict the likelihood of new invasions in stands (woodlots and forests) at the edge of the current range. This model will be verified by searching stands for new invasions and using genetic data to identify the most likely source population of the first shrubs to grow in each stand.
Ultimately their model will enable land managers to predict which stands will most likely be invaded, and therefore focus monitoring, detection, and early eradication efforts at the sites with the highest risk.