Build back better: On the resilience of Ammophila arenaria along the bio-geomorphological dune gradient

Abstract

Coastal dune ecosystems offer a plethora of ecosystem services, but in order to endure the environmental changes as a result of climate change these ecosystems require a certain degree of resilience. To determine the resilience of these ecosystems, we tracked the resistance and recovery of beach grass Ammophila arenaria along the bio-geomorphological dune gradient after disturbance (clipping of aboveground biomass) early in the growing season. As a measure of resilience, we investigated both the resistance, indicated by the capacity for the number and the diameter of the shoots to not decrease following disturbance, and the recovery, indicated by the capacity for the leaves to grow to pre-disturbance levels. We found the resilience of A. arenaria to be dependent on its location along the bio-geomorphological dune gradient, where the beach showed the highest degree of resilience, followed by intermediate resilience at the white dunes and the worst resilience at the grey dunes. Nonetheless, disturbance of A. arenaria early in the growing season generally did not impact the capacity for growth by the end of the season. In addition, we found that the resilience of A. arenaria along the dune gradient varied between the four studied locations, and was dependent on its height above sea-level and distance from the waterline, as well as the salinity, acidity and organic matter content of the soil, and the amount of surrounding vegetation. Combining these findings, we think that the resilience of A. arenaria and consequently that of coastal dune ecosystems, while influenced by various (a)biotic properties, is predominantly dependent on the availability of nutrients along the bio-geomorphological gradient.