Grassland recovery from exotic plant invasion will be long, complicated
Invasive Plant Science and Management recently published the results of a 14-year study of Montana grasslands invaded by leafy spurge, an herbaceous perennial native to Eurasia, and these results indicate that grassland restoration in terms of reducing plant invasion and increasing native diversity will take many years and involve gaining an understanding of a number of variables.
Researchers used flea beetles as a biocontrol agent to destroy leafy spurge. They observed a reduction of the leafy spurge, as well as an increase in native species. However, because the plots used as controls were colonized by the flea beetles, it was not possible to argue that the beetles were directly responsible for the observations.
It had been assumed that successful efforts to remove invasive plants would coincide with the recovery of native diversity to preinvasion levels. The results of this study indicate that this is not the case and that complete restoration of grassland ecosystems will most likely take decades.
Despite the lack of control plots, this study is important because it covers a span of 14 years and documents changes in leafy spurge biomass and native diversity in three sites dominated by native perennial grasses and leafy spurge at the beginning of the study. Furthermore, the data gathered will be helpful to future researchers with similar aims of providing direction on the best way to restore grasslands. It is also noteworthy that the results coincide with a controlled study that was conducted at one of the sites before it was colonized by flea beetles.
It is interesting that two of the sites had a history of herbicide application and reacted differently than the site that had not been treated. These observations mean that it is likely that restoration efforts will be dependent on each particular site's quality and history, as well as such treatment methods as biocontrol.
As invasive plants continue to spread across western North America, reducing native diversity, it will be important to find ways to both halt the spread and restore grasslands to their preinvasion state. This report shows that these tasks will be both arduous and lengthy.
To read the entire study, Effect of Biological Control on Leafy Spurge (Euphoria esula) and Diversity of Associated Grasslands over 14 years, visit http://www.allenpress.com/pdf/ipsm-02-02-151-157.pdf.
Invasive Plant Science and Management is a new journal of the Weed Science Society of America, a non-profit professional society that promotes research, education, and extension outreach activities related to weeds; provides science-based information to the public and policy makers; and fosters awareness of weeds and their impacts on managed and natural ecosystems. For more information, visit http://www.wssa.net/.