Seed dormancy and germination of three grassy woodland forbs required for diverse restoration

Abstract

Restoration is vital for the re-establishment and maintenance of biodiversity of temperate grassy woodlands, but limited understanding of species’ reproductive biology restricts the efficiency of restoration practice. The present study aimed to explore germination cues and seed dormancy of Dianella longifolia R.Br., Dianella revoluta R.Br., and Stackhousia monogyna Labill., three native Australian forb species that have been difficult to germinate in large-scale restoration projects. A series of experiments investigated the effect of various dormancy-alleviation or germination-promoting treatments on germination of these three species. Significant interactions were found between some treatments and germination temperatures for D. longifolia and S. monogyna, but no significant interactions were observed for D. revoluta. At optimal temperatures, scarification treatment produced the highest mean germination for D. longifolia and S. monogyna, and this was significantly higher than for control seeds. Storage conditions (ambient, dry, frozen) did not decrease viability after 10 weeks of storage, suggesting that seeds of all species are likely to be orthodox. To maximise the effectiveness of seed use in restoration programs, it is recommended that scarification of D. longifolia and S. monogyna seed be undertaken to improve field germination. Further work should focus on how to scale up application of the scarification treatment, optimise methods for alleviating dormancy in D. revoluta, and examine the ecological cues that naturally alleviate dormancy and promote germination of these three species.