Response of Terrestrial Arthropod Assemblages to Coastal Dune Restoration

Abstract

To restore historical dune vegetation, substantial effort has been made to remove the invasive plant species, European beach grass (Ammophila arenaria), from coastal dunes of California, USA. However, little effort has been made to examine the response of terrestrial arthropod assemblages to coastal dune restoration. We sampled terrestrial arthropods at 6 dune restoration sites to determine the response of the arthropod communities to vegetation restoration along the central and northern coast of California. Using pitfall traps, we examined restored and adjacent unrestored foredunes and collected reference data from dunes that had not been invaded by European beach grass. Both arthropod abundance and richness were significantly higher on restored and uninvaded dunes than on unrestored dunes. However, we detected no difference in arthropod richness and abundance between restored and uninvaded dunes. The species composition of the arthropod community reflected greater similarity of geographically adjacent sites, rather than similarity within treatments. We conclude that restored dunes provide higher quality habitat for terrestrial arthropods than unrestored dunes dominated by European beach grass, but longer-term studies are needed to determine if restoration efforts will be effective at fully restoring historical arthropod assemblages.

Can Vegetation Removal Successfully Restore Coastal Dune Biodiversity?

“…Detecting community level responses to restoration can be difficult. Indeed, two studies in Californian coastal dunes were unable to show significant assemblage level responses for terrestrial arthropods [32] or plants [24] despite intensive vegetation removal. Our study found only marginal restoration effects in most cases.…”

“…Flora and fauna found on mobile dunes are often psammophilic, endemic species, highly adapted to harsh, xeric sandy conditions, and often form unique assemblages [6,[26][27][28][29][30][31]. Several researchers recognize that dune fixation, whether through succession or intentional re-establishment, can result in adverse consequences for mobile dune species [14,24,25,32,33]. In fact, a review of coastal management actions reported that dune fixation always had a negative impact on coastal species diversity, either through species loss or increase (e.g., invasive species), or changes in composition [19].…”

“…In Wales, rapid dune fixation occurred over the last 60 years after rabbits that had maintained dune perturbation were nearly all wiped out due to extermination and disease [15]. In New Zealand and California, shrub encroachment by invasive species resulted in extensive dune fixation [25,32].…”

Ammophila Invasion Ecology and Dune Restoration on the West Coast of North America

“…Julian [105] found a negative correlation between native solitary bees and A. arenaria at dune systems in northern California. Doudna and Conor [106] sampled six dune systems in California for terrestrial arthropods and found that species richness and abundance were significantly lower in invaded dunes than in restored and uninvaded native dunes. A similar negative correlation was reported by Slobodchikoff and Doyen [107].…”