Demographic responses of the invasive annual grass Microstegium vimineum to prescribed fires and herbicide

Management of invasive species in forests often includes combinations of prescribed fire and herbicides. However for most efficient management, evaluations of these tools should include whole-population responses of targeted plants. In this study, we evaluated how the timing and frequency of prescribed fire and herbicide application affected population growth of the invasive annual grass Microstegium vimineum (stiltgrass) using periodic matrix population models. We conducted an experiment in M. vimineum-invaded deciduous forests in Indiana, USA to compare effects of spring and fall prescribed fires combined with pre- or post-emergent herbicide on M. vimineum populations and to build matrix population models predicting long-term population responses to these management treatments across multiple life-history stages. We found that spring fires were effective at reducing population growth rates during the year of treatment but there was no effect of burning on M. vimineum populations the following year. Similarly, fall prescribed fires were effective at reducing seed production, as well as numbers of seedlings and adults following fires, but had no long-term effect on population growth rates. Post-emergent herbicide alone was the only treatment that reduced M. vimineum population growth beyond 1 year. Seedbank survival had the highest life-stage elasticity across all treatments, indicating that novel management methods specifically designed to exhaust seedbanks for three or more years may be needed to prevent M. vimineum population resurgence after cessation of treatments.