Herbivory by hares as a threat to the native brooms Carmichaelia juncea and C. vexillata

Adult mortality, seed production, and seedling establishment of two species of New Zealand broom (Carmichaelia juncea and C. vexillata) were studied in exclosure trials to determine the level of threat posed by herbivory by introduced mammals. While no effect on mortality was observed for either species, herbivory by hares drastically reduced seed production and subsequent seedling establishment in C. juncea. C. vexillata seemed less vulnerable to herbivore damage due to its plant architecture, as well as the timing and intensity of the herbivore impact. The results of this trial suggest that species characteristics and the dynamics of herbivore impacts need to be considered in planning targeted herbivore control.