Germination Traits Explain Deterministic Processes in the Assembly of Early Successional Coastal Dune Vegetation

The sand dunes found on coastal shores and barrier islands along the Northern Gulf of Mexico are important for protecting inland areas from wind and wave action, especially from tropical storms and hurricanes. The geomorphology of the dunes interacts with the plant community to create this dynamic coastal ecosystem. This study explored the processes that shape the foredunes, the youngest set of dunes where sediments are deposited by winds blowing up from the beach. These sands are thought to be slowed or trapped by early successional vegetation, leading to dune creation and growth. Our results suggest that the vegetative community is strongly associated with distance from the shore, where abiotic conditions are harshest closest to the ocean and gradually reduced moving toward the interior of the island. This deterministic community pattern appears to be maintained by the vegetation's ability to regenerate through time, especially in response to disturbances after heavy wind and wave action. A multifactorial germination experiment revealed strong differences among the germination rates of different species and the effects of salinity on species-specific germination rates. High rates of germination might be beneficial in colonizing open habitats following storms, where high salinity conditions are especially present. Understanding the patterns that shape vegetative community diversity should help guide restoration management in coastal dune systems and shed light on the importance of individual species and their function within the coastal ecosystem.