Trait variability in a widespread and dominant salt marsh grass in a South Carolina estuary

Halophytic plants persist in highly saline environments through a range of physiological and morphological adaptations. Even within a single species, trait expression can vary across environmental gradients such as elevation and salinity. However, while variation in plant height has been relatively well documented in species such as Spartina alterniflora (also known as Sporobolus alterniflorus; smooth cordgrass ) , exploring the extent and patterns of other trait expression across natural environmental gradients provides insight into how multiple environmental drivers shape plant form and function. This study examined trait variability in S. alterniflora , a dominant salt marsh grass along the Atlantic coast of the United States. Plants were surveyed across an elevation gradient along three transects at two sites within the North Inlet–Winyah Bay National Estuarine Research Reserve, South Carolina. Here, we document phenotypic traits (plant height, panicle number and length, and foliar nutrients) and identify those traits that vary across elevation and salinity gradients. Plant height declined with elevation (195 cm/m at site A; 180 cm/m at site B) but showed inconsistent relationships with salinity. Panicle number decreased by 1.1 per PSU in some transects, and panicle length declined with elevation (19.8 cm/m at site A; 16.0 cm/m at site B). Foliar carbon and nitrogen showed no significant trends. These findings improve our understanding of how S. alterniflora phenotypic traits vary relative to marsh elevation and salinity, providing insight into the potential resilience and adaptive capacity of a salt marsh foundation species under changing environmental conditions.