Topography and disturbance influence trait-based composition and productivity of adjacent habitats in a coastal system

Coastal systems experience frequent disturbance and multiple environmental stressors over short spatial and temporal scales. Investigating functional traits in coastal systems has the potential to inform how variation in disturbance frequency and environmental variables influence differences in trait-based community composition and ecosystem function. Our goals were to (1) quantify trait-based communities on two barrier islands divergent in topography and long-term disturbance response and (2) determine relationships between community trait-based composition and ecosystem productivity. We hypothesized that locations documented with high disturbance would have habitats with similar environmental conditions and trait-based communities, with the opposite relationship in low-disturbance locations. Furthermore, we expected higher productivity and lower site-to-site variation with low disturbance. Functional traits, biomass, and environmental metrics (soil salinity, elevation, and distance to shoreline) were collected and analyzed for two habitat types (dune and swale) on two Virginia barrier islands. Our results show that trait-based community composition differed among habitat types and was related to disturbance. Habitats exhibited more similarity on the high-disturbance island in both trait-based composition and environmental variables. Conversely, the low-disturbance island habitats were more dissimilar. We found the habitat with the lowest disturbance had the highest ecosystem productivity and had trait-based communities indicative of highly competitive environments, while the high-disturbance trait-based communities were influenced by traits that indicate rapid recovery and growth. Site-to-site variation was similar in all dune habitats but differed among inter-island swale habitats that varied in disturbance. These results highlight the importance of incorporating trait-based analyses when approaching questions about community structure and ecosystem productivity in disturbance-mediated habitats, such as coastal systems.