In coastal dunes, grasslands persist under stress, related to natural (sand dynamics) and semi-anthropogenic disturbance (grazing by larger mammals) that interact in space and time. Species are expected to show different thresholds towards these disturbances, related to (pre-) adaptations in their evolutionary history. As a result, tolerance towards disturbance will influence plant species and guild composition and changes in community structure are expected to be accompanied by community wide character shifts (CWCS) along the disturbance gradient. Trade-offs between ecological relevant characters are expected to occur at the regional scale, promoting lower local (Alfa) diversity and higher community dissimilarity (Beta diversity). Levels of diversity are expected to be maximal at intermediate disturbance. Additionally, in spatially separated grasslands with similar levels of disturbance, community wide character displacement (CWCD) is expected, accompanied by local trade-offs in ecological traits between species. In the latter Alfa diversity is expected to be higher in comparison to Beta and Gamma diversity.

In order to understand how plant composition (community structure and diversity) is affected by these disturbance regimes, we suggest a study that combines observational and experimental work in which changes in traits and thresholds towards disturbance will be linked to patterns in species composition and species diversity in spatially structured dune grasslands.