LAUSR

Shrub expansion into grassland systems is a global phenomenon. Changing land uses and climate change are the main drivers, with common outcomes including reduced species richness and loss of historical grasslands. Coastal systems are no exception, and along the mid‐Atlantic coast, Morella cerifera (southern wax myrtle) is rapidly expanding into grassland communities. Morella shrubs form dense monospecific thickets. It has been documented that established thickets modify the microclimate resulting in higher soil moisture, low light availability, and moderated temperatures within. It is unknown how M. cerifera affects plant communities that thrive on the edge of these thickets. We assessed these communities for differences in microclimate, vegetation composition, and nutrient availability to quantify effects of living along the shrub edge. Plots were identified in the swale (low‐elevation habitat behind dunes) on Hog Island, Virginia, USA, along the edge of shrub thickets and paired with an adjacent open grassland plot. Trait‐based comparisons were completed on species that overlapped between both communities (i.e., Spartina patens , Solidago sempervirens , Andropogon virginicus , and Panicum amarum ). Along the shrub edge, we found reduced species richness, but increased cover, stem density, and height of grasses relative to open grasslands, with morphological traits indicative of competition along the thicket edge. The microclimate of the shrub edge was highly shaded, had higher soil moisture at lower depths, and cooler summer temperatures relative to the open grassland. Spartina patens was the most dominant species in both communities; however, the relative importance of the species was 250% higher in the shrub edge. As the shrub thicket continues to expand, we expect increased dominance of Spartina patens around the thicket. Shrubs and the modified shrub edge community may impact resilience to sea‐level rise and storms with future climate change.