Response of Naturalized and Ornamental Biotypes of Miscanthus sinensis to Soil-Moisture and Shade Stress

A recent trend in bioenergy-feedstock development includes the use of large-statured perennial grasses whose rapid growth and biomass-accumulation rates in low-fertility conditions make them highly desirable; however, these species tend to have much in common with many invasive plant species. Miscanthus sinensis (Chinese Silvergrass), an extremely popular ornamental grass and candidate bioenergy crop, has naturalized in over half of US states, yet little is known about its environmental-stress tolerance, which is a characteristic important for bioenergy development and invasiveness. Previous studies of Chinese Silvergrass have suggested that the species' enhanced tolerance to shade and drought conditions may be contributing to its invasion success in the US. To test this hypothesis, we conducted a greenhouse study to compare shade and soil-moisture stress tolerance among phenotypically diverse ornamental cultivars and naturalized biotypes of Chinese Silvergrass. We found enhanced plant growth and vigor in naturalized biotypes compared to ornamental biotypes across light levels from 5% to 100% of full sun. We also found that both the naturalized and the ornamental cultivars were not significantly affected by soil-moisture stress, and thus exhibited significant drought tolerance. Greater vigor and performance of naturalized biotypes in low light conditions compared to ornamental biotypes suggest that naturalized biotypes have enhanced shade tolerance, possibly due to hybridization. Our results provide direction for additional evaluations and weed-risk assessments of Chinese Silvergrass that will be critical in preventing future invasions and guide breeding for horticulture and bioenergy.