The Dune enviroment - Riserva Naturale Regionale Guidata Punta Aderci

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The Dune enviroment

THE DUNE ENVIRONMENT

The dunes are characteristic hilly structures of the desert and sandy shores.  The coastal ones develop parallel to the shore, they are composed mainly by fine incoherent sediments carried by rivers (river origin) and waves (sea origin), which transports and re-deposited sediments according to
mainstreams. The dunes are not static structures, they are unstable and they are subject to constant movement and resizing, which are caused by the direction and the strength of the wind. In fact, the wind  pushes the sand particles into the hinterland by dragging or by leaping them and in this way it creates  a windward side with moderate slope and a leeward side with a greater slope . Generally, the slope of the dune facing the sea is hardest hit by the erosive action of wind, while the protected side increases by the accumulation of sand grains. The sand begins to pile up when it meets rocks or plants. The vegetation is therefore of very importance for the formation of coastal dunes, since it creates an obstacle for the advancement of the sand to the hinterland. In this way the formation of embryonic dunes begins, they increase and become stable more and more and form asymmetrical hills that can exceed 10 meters in height.  The first dune, overlooking the sea, is always higher than the next. The following cordons are richer in vegetal cover, represented by shrubs of the Mediterranean maquis.
The cordon dunes are very interesting environments from both an ecological and a landscaping point of view. These ecosystems have a delicate balance of evolution linked to the ongoing transformation of the substrate caused by the wind and the sea, which make difficult the establishment of plants and consequently their stabilization. The action of the man often makes the situation worse with the construction of roads and buildings along the coast or simply walking on the plants growing in the dunes till the demolition of the dunes. However, one of the greatest damage is the construction of artificial barrages upstream of rivers, which have led to a drastic reduction in the transport of sandy sediments that reached the sea, causing the retreat of the beach. In Vasto, this phenomenon is in contrast, because the beach is characterized by an active dynamic of deposition and dune building, facilitated by the deposition of the pier to defend the port of Vasto.

THE VEGETATION OF DUNES.

The coast ecosystem is one of the most selective in nature for the development of plants.  The limiting factors are the wind, which carries tiny droplets of seawater and a multitude of sand grains (sanding action), and the circulating water rich in sodium chloride, which is not taken on by the roots easily. Only those species known as "psammophilous" (from the Greek = psammos sand, file = friend) are able to overcome these conditions. The evolutionary adaptations of plants are the evergreen habit, the succulence of some organs, the thorns and the  tomentum  useful to overcome dry spells;  they need developed root systems in depth, small exposed surfaces  and creeping habit in order to resist the abrasive action of sand carried by the wind;  a very short life cycle helps them  to overcome adverse seasons in the form of seed.
Starting from the sea towards the inside of the area, we find afotica zone of the high tide, where no plants can grow. After this strip there is a deposition zone, where algae, sea grasses and shellfish are beached. The decomposition of these organic substances provides a sufficient amount of nourishment to allow the first pioneer plants to colonize the beach. The annual plants (therophytes) Halo-nitrophilous scrubs, establish a first barrier to the dispersion of the sand.

(Source: Gianfranco Pirone , Aspetti della vegetazione costiera di Vasto)

As you move from the shoreline inland, plant communities arrange themselves in bands parallel to the line of coast. On the beach of Punta Penna, there is the typical succession of psammophilous  plant associations.
1) The Cakileto, the community closest to the shoreline;
2) The Agropireto, inland of the beach at the base of the dunes;
3) The Ammofileto, on the "moving" dunes.


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