Identifying Key Plant Traits and Ecosystem Properties Affecting Wave Attenuation and the Soil Organic Carbon Content in Tidal Marshes

Understanding the relationships among the environment, species traits and ecosystem properties is important for developing management measures that optimize the delivery of ecosystem services (ESs). Here, we identify the most important relationships responsible for the delivery of two key ESs provided by tidal marshes: (1) nature-based shoreline protection through wave attenuation and (2) mitigation of climate change through soil carbon storage. In two tidal zones below and above the mean high water (MHW, Elbe Estuary, Germany) level, we measured environmental parameters, such as soil salinity and inundation, as well as plant traits representing adaptations to hydrodynamic stress and strongly influencing decomposition rates. Multiple linear regression results showed that wave attenuation rates were positively related to aboveground community biomass and stem bending resistance, and soil organic carbon was positively related to stem specific density (below the MHW level). In the tidal zone above the MHW level, soil carbon density was governed by inundation duration and decomposition rates. Our study highlights that (1) ES delivery is not equally spread across tidal marshes and (2) ecosystem management should stimulate the development and persistence of habitat diversity (here, low and high marsh zones) to maximize ES delivery potential. Securing the delivery of the two studied ESs under climate change will depend on providing suitable (landward) space to sustain the functioning of the two marsh zones. In the studied marshes, these services are highly dependent on a few species (i.e., wave attenuation on Schoenoplectus tabernaemontani and Bolboschoenus maritimus and carbon storage on Phragmites australis), and as such, current and future ESs strongly depend on specific species' responses to changing environmental conditions.