Restoration of leafy spurge sites at national parks and wildlife refuges of the northern Great Plains
Leafy spurge is an invasive Eurasian perennial introduced into the U.S. as a contaminant of crop seed in the 1880s and 1890s. It typically forms near-monocultures in rangelands and natural areas of the northern Great Plains. Because all parts of the plant contain latex, it is not consumed by naturally occurring herbivores or cattle, but the biological control program has been successful. Our studies have found, however, that the native vegetation does not necessarily return to sites after leafy spurge has been reduced by biological control. This portion of our long-term studies investigates the mechanisms by which leafy spurge dominates and limits recruitment of native plants. Such information will assist resource managers as they make decisions about the necessity and/or implementation of restoration after reduction of leafy spurge by biological control insects. Results thus far suggest that the seed bank of native plants is not limiting recruitment at sites where leafy spurge has been controlled. Leafy spurge had a larger impact on cover and diversity of vegetation than on the seed bank. Soil legacy effects of leafy spurge, as well as invasive grasses, were found to alter arbuscular mycorrhizal fungi (AMF) colonization rates and community composition in seedling roots of both native and invasive species. Because AMF are key mutualists with most native prairie plant species, restoration of the fungi may be important in successful restoration of native prairies after control of invasive species. Pathogenic fungi likewise respond to plant invasion and influence germination of some native species.
Diane L Larson