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Posted 15 September 2008. PMN Crop News.

Low Nitrogen Levels in Soil Reduce Exotic Plant Invasion and Protect Biodiversity

Weed Science Society of America.

Lawrence, Kansas (September 11, 2008)--A new study published in Invasive Plant Science and Management reports that the nitrogen level in soil is a key factor that determines whether exotic invasive plants will flourish and consequently cause damage to wildlife habitats, ecosystems, and native species.


Managing invasive plant species is important because not doing so negatively affects biodiversity and causes many other problems, including monetary ones. For example, Bromus tectorum, by displacing native grasses, is responsible for the large increase in the number of fires in the western United States and the $20 million spent each year to control them.

Arguing that the degree of plant invasion is dependent on the amount of nitrogen in the soil, the authors present a conceptual model predicting that species with low nitrogen levels are more successful at resisting invasion than are species with high nitrogen levels.

The question, then, becomes how to achieve lower soil nitrogen levels. The authors discuss grazing, mowing, reseeding, and amending soil carbon as potential methods of management. Although burning is also discussed, it is not recommended as a long-term approach.

Rather than supporting the traditional method of treating the symptoms of plant invasion by removing the invasive plants themselves, the authors offer a better approach that involves tackling the problem by altering the ecological processes that allow the invasion to occur in the first place. Ensuring that nitrogen levels in the soil are at the correct low level will hinder exotic speciesí ability to invade native species and as a result minimize threats to biodiversity.

To read the entire study, visit

Invasive Plant Science and Management is a 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