Coastal dunes are highly vulnerable to global climate change because of the tight coupling among island ecological processes, geomorphological processes, and oceanic/atmospheric drivers of disturbance (e.g. hurricanes, nor’easters, sea-level rise). In the process of dune formation, stabilization of sediment is influenced by vegetation with plant roots reducing erosion and aerial stems and leaves intercepting aeolian transported sediments. Changes in dune species or community structure have implications for storm response as species vary in root vs. shoot investment. However, there is still a gap in knowledge as to how belowground structure, traits, and mycorrhizal associations influence interactions with sediment capture and erosion resistance in the dune environment. Our objective is to characterize the belowground components of dune grasses and potential to limit dune erosion along the Atlantic Coast. We characterized belowground traits, biomass, and mycorrhizal associations for three prominent dune building species along the US Atlantic Coast: Panicum amarum, Sporobolus pumilus (i.e. Spartina patens), and Ammophila breviligulata. Samples were collected from locations in the Virginia Coast Reserve Long-Term Ecological Research site and Outer Banks, NC.
Results/Conclusions
Analyses of root traits revealed that the three species form distinctive clusters based on root tissue density (RTD), specific root length (SRL), and surface area to volume ratio of roots (p= 0.021). Sporbolus pumilus and A. breviligulata exhibited significant variation in the relationships between root traits. Conversely, P. amarum demonstrated little variability in root traits with low overall SRL and RTD. These results may indicate that the root systems of A. breviligulata and S. pumilus have greater adaptive flexibility, providing a mechanism for their ability to outcompete P. amarum in coastal dunes. Allocation to roots versus shoots varied significantly by species as did mycorrhizal percent infection rate. Dune morphology and edaphic factors such as soil organic matter were significantly different between dunes dominated by each species. Much of those differences may be explained by species-specific patterns of mycorrhizal development, root traits, and root to shoot investment. Changes in dune traits are then driven in part by competitive interactions between dune species. While most studies on coastal grasses and erosion have evaluated aboveground characteristics, here we show that it is critical to also evaluate belowground traits and competitive interactions as they are important drivers of dune erosive resistance.