Published on: 07/06/16
Short-term mudflat dynamics drive long-term cyclic salt marsh dynamics
Our study aims to enhance process understanding of the long-term (decadal and longer) cyclic marsh
dynamics by identifying the mechanisms that translate large-scale physical forcing in the system into vegetation
change, in particular (i) the initiation of lateral erosion on an expanding marsh, and (ii) the control of
seedling establishment in front of an eroding marsh-cliff. Short-term sediment dynamics (i.e., seasonal and
shorter changes in sediment elevation) at the mudflat causes variation in mudflat elevation over time (dzTF).
The resulting difference in elevation between the tidal flat and adjacent marsh (DZ) initiates lateral marsh
erosion. Marsh erosion rate was found to depend on sediment type and to increase with increasing DZ and
hydrodynamic exposure. Laboratory and field experiments revealed that seedling establishment was negatively
impacted by an increasing dzTF. As the amplitude of dzTF increases towards the channel, expanding
marshes become more prone to lateral erosion the further they extend on a tidal flat, and the chance for
seedlings to establish increases with the distance that marsh has eroded back towards the land. This process-based
understanding, showing the role of sediment dynamics as explanatory factor for marsh cyclicity, is
important for protecting and restoring valuable marsh ecosystems. Overall, our experiments emphasize the
need for understanding the connections between neighbouring ecosystems such as mudflat and salt marsh.