Effects of Season and Frequency of Prescribed Fire on the Demography of Centaurea maculosa, (Spotted Knapweed), in a Midwest Prairie RestorationEPA Grant Number: U916007
Title: Effects of Season and Frequency of Prescribed Fire on the Demography of Centaurea maculosa, (Spotted Knapweed), in a Midwest Prairie Restoration
Investigators: Emery, Sarah M.
Institution: Michigan State University
EPA Project Officer: Lee, Sonja
Project Period: January 1, 2001 through January 1, 2004
Project Amount: $83,988
RFA: STAR Graduate Fellowships (2001) RFA Text | Recipients Lists
Research Category: Fellowship - Terrestrial Ecology and Ecosystems , Academic Fellowships , Ecological Indicators/Assessment/Restoration
The objective of this research project is to understand the unique constraints that invasive exotic species present in restoration sites to develop effective ways of managing invasive species populations, while promoting native biodiversity. Oak savanna and prairie were once common throughout the upper Midwestern United States, but agriculture and urbanization have destroyed all but a few remnants of these distinctive ecosystems. Restoration of these threatened natural areas is essential for protecting native biodiversity and ecosystem functions, and provides unique opportunities to explore experimentally the basic processes of ecology. Restoration projects often are complicated by the presence of invasive exotic species that depend on disturbances, such as those used in traditional restoration practices, to become established and persist.
Ecologists and land managers often use prescribed fire to restore and maintain native plant diversity in prairie remnants of the Midwest, although effects of burning on exotic species in such sites are not well documented. Depending on the timing of management relative to individual species' life cycles, different seasons or frequencies of fire can have very different effects on population dynamics of species within these communities. Centaurea maculosa (spotted knapweed) is one exotic invasive that is an important economic pest in the western United States, and which is becoming a problem in the Great Lakes Region. I used annual censuses and population matrix analysis to evaluate the demographic consequences of burning on Centaurea maculosa (spotted knapweed) populations in a Michigan prairie restoration experiment. Treatments began in 2000, and varied in season of burn (spring, summer, or fall) and frequency (annually or biennially). Annual summer burning was the only treatment effective at reducing C. maculosa population growth rates. A Life Table Response Experiment analysis showed that summer burning reduced population growth by reducing reproduction in adult plants. Biennial summer burning and spring and fall burning at any frequency had little effect on population size, structure, or growth. Elasticity analyses showed that, independent of treatment, nonreproductive adult survival tended to the most important life stage influencing population growth. This suggests that future management attempts that target adult survivorship also may be successful in controlling C. maculosa in Midwestern grasslands. Annual summer fires may provide adequate control if the burn regime can be sustained, although responses of the entire community also should be considered.