Schönebeck, J.-M., Bunzel, D., Paul, M., Schlurmann, T. (2026). Plant trait diversity buffers soil moisture dynamics on coastal dikes during drought periods. PLOS ONE 21(3): e0345552. https://doi.org/10.1371/journal.pone.0345552
Vegetation makes a significant contribution to the stability of dikes by anchoring the revetment with its roots, reducing susceptibility to erosion, and regulating soil moisture and temperature. However, against the backdrop of declining biodiversity and increasing weather extremes, the focus is shifting not only to traditional dike greening but also to the growing need for additional approaches that can complement existing coastal protection measures. In particular, the functional diversity of plant traits is increasingly being discussed as a key factor in the resilience of ecosystems to droughts and other climate impacts.
In the current study by Schönebeck et al., researchers investigated the extent to which plant communities of varying diversity affect soil properties and, consequently, the stability of dikes.
Two seed mixtures with different species compositions were sown on a summer dike in Butjadingen on the North Sea coast: one mixture with a high proportion of herbs (“Herb Mix”: 98% herbs, 2% grasses) and one with a high proportion of grasses (“Grass Mix”: 25% herbs, 75% grasses). The goal was to investigate the effects of the plant compositions on the microclimate on the dike. To this end, soil moisture and temperature were continuously recorded and analyzed over a period of one year, during which two drought periods occurred.
The results show that soil moisture in the area with the herb-rich “Mix-Kraut” vegetation was higher throughout the entire period than in the grass-dominated “Mix-Gras” area (on average by 0.054 m³ m⁻³ ± 0.018). During the first drought period in June 2023, the soils in both dike sections dried out significantly, although soil moisture in the “Mix-Kraut” vegetation area remained higher at the end of the drought period. At the same time, high soil temperatures (up to 31.9 °C) occurred in the “mixed grass” vegetation area at a depth of 4 cm, leading to greater diurnal fluctuations (averaging between 17.0 and 27.5 °C) than in the “mixed herb” vegetation (averaging between 16.4 and 21.9 °C).
Mulch mowing was carried out prior to the second drought period in September 2023. As a result, diurnal fluctuations in soil temperature increased, particularly in the “mixed herb” vegetation, so that these fluctuations were greater after mowing than in the “mixed grass” vegetation. Soil moisture, on the other hand, remained at a higher level in the “mixed herb” vegetation area even after mowing and during the second drought period.
The results suggest that functional plant traits, in particular, play a decisive role in the microclimate on dikes. The taller growth and greater diversity of leaf structures in the “mixed herbaceous” vegetation appear to have led to increased shading, improved cooling through evaporation, and reduced wind circulation at ground level. As a result, soil temperature fluctuations in the herb-rich vegetation were less pronounced prior to mowing. Furthermore, herbaceous species with deeper root systems allow for better access to deeper water resources, thereby contributing to the stabilization of soil moisture and temperature. Overall, the results show that both vegetation with more diverse functional properties and adapted management (e.g., mowing based on weather forecasts) can help improve the resilience of dike systems to extreme weather events.
For further information, please contact Jan-Michael Schönebeck at the Ludwig-Franzius Institute for Hydraulic Engineering and Estuarine and Coastal Engineering at Leibniz University Hannover via email at schoenebeck@lufi.uni-hannover.de.
