# Can Vegetation Removal Successfully Restore Coastal Dune Biodiversity?
## 4 Discussion
### Effect of Fixed-Dune Treatment  
A recent review of coastal restoration projects revealed that fixed dunes are the most frequently restored dune type (54%), followed by semi-mobile dunes (30%), mobile dunes (27%) and dune slacks (16%; [2]. However, the most frequently used restoration mechanism was revegetation (42%), while destabilization or vegetation removal only accounted for less than 5% of restoration projects. Removal methods varied among removal experiments.  
The extensive and intrusive removal of perennial vegetation in a grid formation on fixed dunes had virtually no effect on most of the parameters monitored, rejecting hypothesis \(H_{3}b\), \(H_{4}a\), and \(H_{6}\)_for_ this treatment type. The only consistent effect was a reduction in the average abundance of all taxa (\(H_{3}a\)); richness and composition were not affected. That said, at the temporal scale, some weak responses of reptiles were observed both for the IS and for composition in the first two years after treatment, suggesting some support for resilience under Hypothesis \(H_{4}b\). All other taxa showed very limited response to fixed dune treatment, indicating strong resistance to change (supporting Hypothesis \(H_{4}c\)). Detachment from mobile dune assemblages may explain this lack of response. In addition, the dunes from which vegetation was removed are surrounded with dense interdune vegetation, including tall sycamore trees, which reduce wind speed, preventing sand migration and potential recolonization from neighboring areas. Thus, sand deposition in the treated dunes was minimal, and sand enriched with nutrients and organic matter remained present after the vegetation removal. Throughout Europe, several coastal dune management schemes involving vegetation removal achieved partial success in restoring dune mobility, from a geomorphological perspective [6; 15; 31; 40].  
Evidence suggests that soil processes in fixed dunes have changed the soil irreversibly [19]. In experimental dune restorations, removal of vegetation and topsoil in the slacks and inner dunes often fail to restore aeolian activity due to the groundwater table and the usually moist conditions at the surface, which prevent saltation [4]. In Mediterranean coasts, wind-related variables may only be of minor importance compared to soil properties [98]. Encroachment and intended establishment by grasses, shrubs and woody plants have accelerated in response to high rates of nitrogen deposition [33; 99; 100; 101; 102]. Top-soil inversion has become a popular method for restoration of inland dunes in recent years, where topsoil is buried under a layer of subsoil, so that the original layers are intact but their position in the profile is changed [103; 104]. Results indicate that inversion can successfully lower surface soil fertility and reduce competition, creating a nutrient-poor space for the establishment of early-successful stage species in calcareous grasslands and sand dunes [105; 104]. Ploughing and topsoil inversion enhanced lichens and annual plants, lowered organic matter and increased rabbit activity compared to control plots in grass health habitats [106; 107]. Thus, topsoil removal within the grid formation applied on Nizzanim fixed dunes may have created a better response at the community level.