Lingering Effects of Invasive Species

By Susan Littlefield

The ecological disruption caused by invasive plants species is a worldwide problem. The cost of the environmental and economic impact of these invaders is estimated to be in the neighborhood of $1.4 trillion annually! Much research is being done to come up with strategies to control the spread of undesirable plants and minimize their impact on natural ecosystems. Now new research suggests that simply removing invasive species may not return plant communities to their pre-invasion condition.

Part of developing control strategies for invasive plants involves understanding the characteristics that allow certain species to become invasive in the first place, factors such as freedom from natural enemies, disturbance in the environment, and the ability of plants to release substances that prevent competing plants from growing.

To study how the interactions between all of these factors affect the success of an invasive species, investigators from the University of California and the University of Wisconsin studied invasive velvetgrass, Holcus lanatus,(illustrated) and its effect on a native daisy, Erigeron glaucus, in California. As described in an article in Science Daily on August 10, 2011, they found that direct competition between velvetgrass and the daisy accounted for much of its initial success due to the dense growth of the grass and its abundant propagules.

But they also found that velvetgrass altered the structure of the native community of soil organisms, specifically the mycorrhizal fungi in the soil. This change reduced the benefits of the mycorrhizae to the native daisy without having any negative impact on the velvetgrass. And the changes in the soil community persisted even after the velvetgrass was removed, potentially affecting the reestablishment of the native plants.

These findings suggest that studying the negative effects invasive species have on the ecology of the soil has important implications for researchers who are looking at ways to mitigate their effects.

To read more about the effects of invasive plants even after removal, go to: Science Daily.

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