Erosion protection by winter state of salt marsh vegetation

Abstract The inclusion of coastal ecosystems in coastal protection strategies is highly desired, but for temperate regions it is hampered by uncertainty about the provision of relevant ecosystem services over the annual growth cycle. This flume study compared winter stages of the two salt marsh species Spartina anglica and Elymus athericus with and without above ground biomass to bare soil to assess their protection service against vertical bed erosion in the surf and swash zone. Results yielded no effect of the above ground biomass on mean erosion, even though the species responded differently with E. athericus buckling and S. anglica withstanding the hydrodynamic forcing. Equally, no significant differences were observed between species which is attributed to the comparable dry root biomass and soil bulk density of the used vegetated patches. While this similarity does not allow for establishment of quantitative relationships, the results suggest a species independent erosion protection efficiency persisting throughout the year. This has the potential to simplify the consideration of erosion protection by salt marsh in coastal protection strategies, as it alleviates the need for detailed differentiation on species or seasonal level of this ecosystem service.