Seeds self-burial, germination, and seedling survival for a species with hygroscopic awns (Illinois).

This study was conducted to: determine the deawning threshold to allow for self-burial; and to investigate how deawning influences germination and seedling survival for beach three-awn grass (Aristida tuberculosa). We predict that progressive deawning will hinder seed self-burial, seed germination, and seedling establishment for this species. We selected beach three-awn grass for this study because: it has multiple awns; it is a rare species in many states across its range in the USA, and this information could aid in cx situ reintroduction projects in habitats such as oak savanna and dry sand prairie; and previous research by Collins and Wein (1997) [See Mass allocation and self- burial of Aristida tuberculosa florets (1997), 24, 306-311] demonstrated that completely to partially buried awned seeds of beach three-awn grass will germinate. We collected seeds for three trials at the Lost Mound Unit of the Upper Mississippi River National Wildlife and Fish Refuge, Illinois, USA in October 2006, and trials were conducted in 2007. Germination occurred in both buried and unburied seeds, and no significant differences were found among the awn removal treatments. This result is different from that of Collins and Wein who demonstrated that for beach three-awn grass, unburied awnless seeds did not germinate, unlike buried seeds with awns intact. Also, although we found no differences among the awn removal treatments: most seeds that germinated became seedlings, except for deawned unburied seeds, which died of desiccation. Because our study was conducted under controlled conditions, the impact of awn removal and subsequent failure to self-bury on seed germination and seedling establishment could have been negated, and therefore should be further examined in a natural setting where other factors (for example, seed predation, seed damage by fire, and seedling desiccation) might produce different outcomes.