Date of this Version
Smooth brome (Bromus inermis Leyss.) is an aggressive invader of fescue prairie; however, little information is available on the germination ecology of this exotic perennial relative to native flora. This information is needed to understand the processes of invasion and to develop strategies to curb the spread of smooth brome. Germination of smooth brome and plains rough fescue (Festuca altaica subsp. hallii (Vasey) Harms) seeds was compared under various temperature regimes, levels of water stress, and light. Germination of both species was severely restricted by water stress, but not by temperatures between 5 and 25°C. Smooth brome had higher germination over a broader range of temperatures and water stress than plains rough fescue. When incubation temperatures were decreased from 25 to 5°C, total germination was reduced for plains rough fescue relative to temperatures that were increased from 5 to 25°C; germination of smooth brome was similar under increasing or decreasing temperatures. At a given level of water stress at 10 and 20°C, plains rough fescue germination was unaffected by light and darkness. Germination was higher for smooth brome in dark than in light at 10°C, but at 20°C it was generally similar in light and darkness. Germination of smooth brome over a wide range of temperatures, light, and moisture conditions increases the probability that requirements will be met in heterogeneous seedbed conditions. Smooth brome is well adapted to germinate and establish in prairie dominated by plains rough fescue.