Soil bioengineering techniques for Mediterranean coastal dune restoration using autochthonous vegetation species

Coastal dunes are extremely fragile and threatened ecotones, which play a key environmental role in terms of functional connection between terrestrial and marine ecosystems. To counteract the hydrogeological vulnerability in coastal risk areas, reliance can be made on soil bioengineering techniques, consisting of planting native species in combination with natural inert materials. These interventions involve the use of typical Mediterranean plant species, which are fundamental for increasing soil surface protection as well as for their ecologic function in coastal dune consolidation. Monitoring studies on plant growth parameters are useful to assess the suitability of the different species to be used in soil bioengineering works. Hence, this study aimed to (i) identify some Mediterranean herbaceous and shrubby plant species to be used in coastal interventions, (ii) evaluate different plant propagation methods and short-term growth parameters, and (iii) provide useful insights into field management strategies before and after transplanting.Juniperus phoenicea L., Juniperus macrocarpa Sm., Pistacia lentiscus L., Tamarix africana Poir. and Tamarix gallica L. were the selected shrubs species while Ammophila arenaria (L.) Link, Sporobolus pungens (Schreb.) Kunth., Agropyron junceum (L.) P. Beauv., Eryngium maritimum L., Calystegia soldanella (L.) R. Br., and Pancratium maritimum L. were the selected herbaceous species. As to shrubs, seeds and cuttings proved the best propagation methods with an efficiency of up to 90%. Agamic propagation methods, on the other hand, were the most efficient (80-90%) for the herbaceous species. After transplantation, all the species showed an adaptation period to the new climatic and edaphic conditions. In particular, Pistacia lentiscus L. was found withered with the presence of some radical shoots.