Mowing as a management tool to control invasive Carduus nutans and Carduus acanthoides

Disturbance is commonly thought to promote biological invasion. However, disturbance can also be used as a management tool to control invasive species. We conducted a mowing experiment to investigate the effects of different disturbance aspects (frequency, intensity and timing) on the growth, survival and reproduction of two invasive thistles, Carduus nutans and Carduus acanthoides. Our results show that mowing removed apical dominance and therefore induced more stems. A single mowing application when plants were bolting had little effect on survivorship and flower number; however, it delayed peak flowering and reduced both maximum plant height and flower head diameter. The different aspects of disturbance interacted significantly to affect the overall invasion success of the two thistles. Our results suggest that certain combinations of the various aspects of disturbance may generate improved management outcomes.