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Marram grass, exotic species and dune development

Objectives of this project


If the emergence of invasive species impact marram grass vitality, the formation of dunes and therefore also the resilience of our sea dunes is compromised. With Endure we map both the distribution of these exotic species and their relationship with the environment. This is done on the basis of targeted inventories and experiments. In order to get an as complete as possible picture of the emergence of these species, we call on everyone to help us map them out!

Marram grass as a sand binder

The total sand supply from the (high) beach is the most important component for dune development on a large scale. The present marram grass will be able to fix part of this sand, which will result in a local growth of the dune around the marram tussocks. This sand accumulation has the effect that the marram grass can rise, which translates into an increase in the biomass of the these tussocks and consequently a greater capacity to fix sand. Sand drift and marram grass growth are therefore positively coupled on a small scale.
Increase in the biomass and cover of marram grass on a larger spatial scale will, however, locally inhibit the sand supply, causing the grass to die off and be replaced by stable herbaceous vegetation and thickets (hyperstatic dune); or allow spraying again if sand supply is very high (dynamic dune). The dying of marram grass is the result of an increased colonization by plant parasitic nematodes. When sand is accumulated, the plant will be able to avoid these pathogens by growing in height along with the dune. In this way the roots develop in a pathogen-free zone.

Mobirise

Invasive exotic plants and marram grass

Invasive exotics can compete with native species. In the dune this is done through interactions in the soil: invasive species such as the hottentot fig will change the soil during establishment due to the emission of toxic substances but also biological enemies, and thus hinder the establishment and growth of native species. In the figure below you can see the direct impact of these soil changes due to the hottentot fig on the growth (top figure) and survival of marram grass (bottom figure). Experiments were repeated at two locations. The black bars show the growth and survival on soils that were already conditioned by the invasive exotic; the white bars show the reference values ​​on sand that was not affected by the exotic.

Mobirise

References

DE LA PEÑA, E., DE CLERQ, N., BONTE, D., ROILOA, S., RODRÍGUEZ-ECHEVERRÍA, S. & FREITAS, H. (2010). Plant-soil feedback as mechanism of invasion by Carpobrotus edulis. Biological Invasions 12: 3637-3648

VAN DER PUTTEN W. H., VAN DIJK, C. & PETERS, B. A. M. (1993). Plant-specific soil-borne diseases contribute to succession in foredune vegetation. Nature 362, 53-56.