In the Mid-Atlantic region, sea-level rise is accelerating at 3-4 times the global average rate, provoking rapid habitat shifts in many coastal areas. As salt water intrudes on upland habitats, tidal wetland species are colonizing space opened up by upland dieback and can even establish in coastal forest understory prior to canopy death. One such species is the high marsh foundation species salt marsh hay, Spartina patens, which has been documented and well-studied in marsh, dune, and swale, but not understory forest, environments. Through surveys of coastal ecotones, we have identified populations of salt marsh hay colonizing forested uplands. We established plots in adjacent marsh and forest understory areas at three field sites on the Delmarva peninsula where S. patens is a dominant species and conducted a reciprocal transplant experiment in order to address the following questions: a) How do environmental conditions for S. patens differ between marsh and forest habitats? b) How do S. patens traits differ between these habitats? c) Are the trait differences we see a product of phenotypic plasticity in response to environmental differences, or carry over of traits from their habitat of origin?
Results/Conclusions
We found lower salinity and light availability in the forest as compared to the high marsh, and these upland understory conditions corresponded with fewer stems, but greater height and specific leaf area of S. patens plants. There was no flowering observed in forest plots, which could have important implications for population demographics of this sexually and asexually reproducing species as it migrates into forest. Though some traits showed an effect of their habitat of origin, many exhibited strong phenotypic plasticity when transplanted between habitats. This plasticity may prove crucial to the species’ resilience to future change.