P.M.J. Berghuis1,2*, V.C. Reijers2, A.G. Mayor3, J. van de Koppel1,4, M. Rietkerk2, T. van der Heide1,4
1 NIOZ, The Netherlands; 2 Utrecht University, The Netherlands; 3 Complutense University of Madrid, Spain; 4 Groningen University, The Netherlands
*Corresponding author: p.m.j.berghuis@uu.nl
Introduction
Biogeomorphic systems are formed by the dynamic interplay between living organisms and geomorphological processes (Viles, 1988). In coastal ecosystems, these interactions are particularly pronounced, as engineering organisms - from marsh vegetation to reef-building corals - actively shape the shoreline. Because of the ecosystem services they provide, including biodiversity, freshwater provision, carbon storage, and flood defense, biogeomorphic coastal landscapes are of great value (Barbier et al., 2011).
In many biogeomorphic systems, a positive feedback is present between the engineering species and its environment. An archetypical example of such a feedback is found in coastal dune systems. Pioneer dune grasses initiate dune formation by trapping airborne sediment. This sediment buries the grasses, which stimulates plant growth, thereby increasing their sand-trapping capacity (Bonte et al., 2021; Nolet et al., 2018). The strength of this feedback is species-specific and is influenced by the spatial organization of aboveground plant biomass Lammers et al., 2023; Reijers et al., 2021). Although we have a solid understanding of how individual plants can build dunes, the interactions between these plants, and the embryonic dune bodies they create, are less well understood. The initial spatial organization of individual dune grass patches could play a crucial role in shaping the biogeomorphic landscape (Schwarz et al., 2018).
Objective and Methods
In this work we will look beyond individual dune formation, and investigate the role of the initial spatial organization of vegetation patches on subsequent dune build-up. We hypothesize that, much like the shoot organization within an individual patch (Reijers et al., 2019), the spatial distribution of dune grass patches can steer local sand trapping efficiency at the landscape scale. Using high-resolution aerial imagery and elevation models, we tracked the development of a large natural dune system in the Netherlands over a 10-year period. We extracted the spatial characteristics of the initial embryonic dune field and assessed its effect on subsequent dune build-up and landscape formation.
Results
Our results indicate that, rather than the initial size of embryonic dunes, the proximity to neighboring embryo dunes strongly influences dune build-up on a landscape scale. We observed a clear relationship between the local density of dune grass patches and subsequent dune height. Following a S-shaped curve, patches in areas of low density exhibit only limited height accumulation, while increasing density leads to a rapid rise in future dune height that eventually flattens of at the highest densities. In our study system, the strength of this S-shape relationship intensifies over time and displayed a dominant spatial scale of 3–13 meters. Our findings demonstrate the persistence of dune grass patches, and highlight how the initial spatial distribution of embryonic dunes can serve as a blueprint for future dune formation. Moreover, they illustrate the importance of biogeomorphic feedbacks that extend beyond the scale of individual plants, and their role in shaping coastal landscapes.
References
Barbier, E. B., Hacker, S. D., Kennedy, C., Koch, E. W., Stier, A. C., & Silliman, B. R. (2011). The value of estuarine and coastal ecosystem services. Ecological monographs, 81(2), 169-193.
Bonte, D., Batsleer, F., Provoost, S., Reijers, V., Vandegehuchte, M. L., Van De Walle, R., ... & Hillaert, J. (2021). Biomorphogenic feedbacks and the spatial organization of a dominant grass steer dune development. Frontiers in Ecology and Evolution, 9, 761336.
Nolet, C., Van Puijenbroek, M., Suomalainen, J., Limpens, J., & Riksen, M. (2018). UAV-imaging to model growth response of marram grass to sand burial: Implications for coastal dune development. Aeolian Research, 31, 50-61.
Lammers, C., van de Ven, C. N., van der Heide, T., & Reijers, V. C. (2023). Are ecosystem engineering traits fixed or flexible: A study on clonal expansion strategies in co-occurring dune grasses. Ecosystems, 26(6), 1195-1208.
Reijers, V. C., Siteur, K., Hoeks, S., van Belzen, J., Borst, A. C., Heusinkveld, J. H., ... & van der Heide, T. (2019). A Lévy expansion strategy optimizes early dune building by beach grasses. Nature communications, 10(1), 2656.
Schwarz, C., Gourgue, O., Van Belzen, J., Zhu, Z., Bouma, T. J., Van De Koppel, J., ... & Temmerman, S. (2018). Self-organization of a biogeomorphic landscape controlled by plant life-history traits. Nature Geoscience, 11(9), 672-677.
Viles H.A. (1988). Biogeomorphology. Blackwell, Oxford, UK.
