Coastal vegetation on sandy substrates of the region Zacharo beach (western coast of Peloponnese Greece)
Investigations in 1992, manuscript 2004
Wilhelm-Raabe-Weg 6, D-30938 Burgwedel, Germany
General dune sequence along the Mediterranean coast line (citing Mayer, A. 1995: Comparative study of the coastal vegetation of Sardinia (Italy) and Crete (Greece) with respect to the effects of human influence. Libri Botanici, Vol. 15, pp.139-140, 143):
The waves of the surge slow down along the rising profile of the sandy beach. Organic residues are deposited along the high water mark, that indicates the furthest extent of waves during winter storms. The first type of vegetation in front of the beach growing along the drift line is characterized by the annually restoring plant communities of the Cakiletea maritimae, which forms a herbaceous, sparsely growing belt-like type of vegetation. It is also present at the rim of estuaries and salt lakes. According to the rough environmental conditions of the drift line only a small number of annual species have adapted to this habitat. They can cope with high concentrations of salt in the substrate and show succulent or leathery leaves. These species mainly belong to the Chenopodiaceae and Brassicaceae. They are known for their property of growing on nitrogen-rich substrates. The most characteristic species in this type of vegetation are Cakile maritima, Salsola kali, Euphorbia peplis and Polygonum maritimum.
The first occurrence of perennial plants after the drift line forms an obstacle for the accumulation of sand. These small dunes are called initial dunes or embryo dunes. In general, the evolve in the back of small pioneer tufts of the perennial grass Agropyron junceum. Less frequently observed, but also effective for the establishment of initial dunes were species such as Eryngium maritimum, Otanthus maritimus, Limonium graecum and Silene succuleneta.
In favourable conditions initital dunes may stabilize and increase considerably in size. This dune strip is called foredune and receives considerable amounts of salt spray. They form a row of front facing dunes in parallel position to the shore line. Foredunes are frequently built up in a “sandwich-structure” of Posidonia residues and sand layers. This kind of structure is exposed in cases of partial dune erosion during winter storms. Foredunes can vary significantly in their shape and size. Depending on the supply of sand foredunes vary from a low rampart-like system to distinct and large star dunes. The number of plant species, in particular on the back of the foredune increases if compared with the initial dunes. The vegetation is dominated by the plant community of the Cypero mucronati-Agropyretum juncei Cyperus mucronatus = Cyperus capitatus). Common species found on this part of the beach are Agropyron junceum, Cutandia maritima, Otanthus maritimus, Medicago marina and Ammophila littoralis.
A field of dunes develops in the shadow of foredunes. They are called yellow dunes according to the colour of their surface caused by the patchwork of sand and sparse vegetation. The plant cover in this dune belt is less penetrated by salt spray compared with the vegetation on foredunes. The sand is still mobile and gradually stabilizes towards the back of the beach. The general dune types are wind shadow dunes and wake dunes. This area is charcterized by plant communities of the Otantho marinae-Ammophiletum littoralis and the Crucianelletum maritimae.
Grey dunes develop by the sand blown across the yellow dunes. The expression grey dunes indicates the grey tone of the sand in this area. The increased amount of humus in the sand caused by the decomposition of plant matter, but also the increased amount of silt is responsible for the grey tone of the sand. In the area of grey dunes the speed of the wind, the grain size of the sand and the influence of the salt spray decreases, whereas the number of plant species increases as a consequence to the lower environmental stress. The sand of grey dunes is generally stabilized and shows little capacity to migrate. According to the improved living conditions the vegetation cover can afford greater variation as observed on foredunes and yellow dunes. The grey dunes in Sardinia are mainly covered by pelouse vegetation of the Helichryso-Crucianellietalia and juniper scrub representing the vegetation of the Pistacio-Rhamnetalia alaterni. A similar type of pelouse is found in Crete, differentiated from the latter by the presence of Centaurea spinosa and Choridothymus capitatus. This vegetation type is allocated to the Cisto-Micromerietea. The dune grassland and dune heath on grey dunes does not occur in Sardinia and Crete, due to the dry climatic conditions.
Method and results
Dune system shown by the example of Zacharo, western coast of Peloponnese (Greece) (F. Erlinghagen)
In order to show the sequence of species (and consequentely the plant communities along a gradient), vegetation transects were made across the vegetation of the dune system Zacharo, western coast of Peloponnese in april 1992. They consist of the continuation of phytosociologic releves made on plots of one square metre in size (technique described by Braun-Blanquet 1964). Some phytosociologic releves are shown in table 1.
Transect across the vegetation of the dune system Zacharo, western coast of Peloponnese in April 1992. The transect forms a W - E cut across the profile of the dune system.
|Distance to the sea (m)||40||45||60||90||105||110||130||150||155||160||170||180||190||230|
|General cover of plants (%)||15||<5||80||20||20||10||50||30||90||80||70||20||20||20|
|Juniperus spp. (seedling)||+|
|Pinus halepensis (juv)||r|
Further plant species in the investigation area: Pseudorlaya pumila, Lotus halophilus, Medicago littoralis, Cutandia maritima, Bromus madritensis, Euphorbia paralias, Salsola kali, Xanthium strumarium, Polygonum maritimum, Arundo donax, Ephedra distachya, Erodium ciconium, Anagallis arvensis, Medicago cf. polymorpha, Hedypnois rhagadioloides, Posidonia oceanica, Herinaria hirsuta
Fig. 1 Euphorbia paralias (Euphorbiaceae), in the background Otanthus maritimus (Asteraceae), dune system near the town of Zacharo, western coast of Peloponnese, April 1992
Fig. 2 Pancratium maritimum (Amaryllidaceae), withered, infructescence in April 1992
Fig. 3 Medicago marina (Fabaceae) with yellow flowers, Silene colorata (Caryophyllaceae) with pink flowers, Cyperus capitatus (Cyperaceae) and Sporobolus pungens (Poaceae), in the background tufts of Agropyron junceum (Poaceae) in April 1992
Fig. 4 View of the dune system with Ammophila littoralis (Poaceae) and Otanthus maritimus (Asterceae), in the background grey dunes with Coridothymus capitatus (Lamiaceae)
Fig. 5 Ammophila littoralis and Otanthus maritimus dominate in spring
Fig. 6 Grey dunes with Coridothymus capitatus, an important nectar source for honey bees and basis for the well-known Thymeli honey in Greece
Fig. 7 Choridothymus capitatus builds a globe-shape cushion, this plant form is typical for the Mediterranean area
Fig. 8 Pinus halepensis in contact to the dune system
The coastal environment of the Mediterranean basin is influenced through human actvities for thousends of years, especially through agricultural activities (grazing of sheep and goats, clearing the forest for crops, the deliberate use of fire e.g.), nowadays additional through the large scale developments for tourism, urbanization and spread of industrial zones. The dune system near Zacharo is in danger too, through building houses, riding motorbikes and other free time activities.
I express my thanks to DAAD for financing my stay in Greece (results of investigations about producer of honeydew in Greece on this homepage). To Mr. Dr. Armin Jagel (Bochum, Germany). I thank for having determined critical plant species.