Escaped Miscanthus sacchariflorus reduces the richness and diversity of vegetation and the soil seed bank

Prioritizing management efforts and funds for invasive species relies upon knowledge of their ecological impacts. Often, however, novel species have unknown effects and can exhibit long time lags before proliferating, making early management decisions difficult. The grasses Miscanthus sinensis, Miscanthus sacchariflorus, and their sterile hybrid M. x giganteus have been introduced to North America and elsewhere for horticultural and agricultural purposes, but little is known about their impacts on resident vegetation upon escape from cultivation. We compared the vegetation communities and soil seed bank of paired areas invaded and uninvaded by escaped Miscanthus sacchariflorus at ten sites in Ontario, Canada. Invaded plots had very few species other than Miscanthus sacchariflorus and had lower plant species abundance, richness, and diversity than did uninvaded plots, and effects were greater on the vegetation than on the seed bank. Invaded plots also had more live and dead standing biomass, taller vegetation, and greater litter biomass, along with decreased light penetration to the soil surface than in uninvaded plots. However, Miscanthus sacchariflorus did not produce a germinable seed bank. Our results suggest that the regional spread of Miscanthus sacchariflorus is currently limited by a lack of seed production/viability, but its occurrence along disturbance-prone roadways and drainages facilitates its local vegetative spread. The strong negative effects of Miscanthus sacchariflorus on the resident plant community should be considered in risk assessments and management planning for this and other Miscanthus species.