Germination phenology of some Great Basin native annual forb species

Great Basin native plant communities are being replaced by the annual invasive cheatgrass Bromus tectorum. Cheatgrass exhibits a germination syndrome that is characteristic of facultative winter annuals. Although perennials dominate these communities, native annuals are present at many sites. Germination timing is often an important predictor of competitive interactions, and might determine whether the use of annual species in restoration efforts will be successful. I used a laboratory experiment to determine whether a suite of native annuals exhibit winter or spring annual germination syndromes. Seeds of Amsinckia menziesii var. intermedia, Amsinckia tesselata, Blepharipappus scaber, Descurainia pinnata, Eriastrum sparsiflorum, Lappula occidentalis, Mentzelia veatchiana and Plagiobothrys tenellus were tested for dormancy, and for responsiveness to light, cold stratification and dry after-ripening. Species that would be expected to be most similar to cheatgrass are those that have no requirement for cold stratification and are therefore likely to germinate under autumn or winter conditions. The species that clearly met this criterion in this laboratory study were A. menziesii var. intermedia, A. tesselata, D. pinnata and L. occidentalis. In contrast, B. scaber, E. sparsiflorum, M. veatchiana and P. tenellus had their highest germination after cold stratification and would be expected to be spring germinators. Blepharipappus scaber was not coaxed out of dormancy to a great degree by any of the treatments I applied and may exhibit cue-non-responsive dormancy. Field seed burial experiments, as well as experiments examining the competitive ability of these annuals versus cheatgrass will further inform us about their potential for success in restoration seedings.