Southwestern Mediterranean Vegetation

Plant Formations in the Southwestern Mediterranean BioProvince

Peter Martin Rhind

Southwestern Mediterranean Pyrus mamorensis Forest Forest characterized by scattered trees of the endemic pear Pyrus mamorensis (Rosaceae) is best exemplified by the Mâmora Forest of Morocco. An open, xerophilous forest of deep sand it includes various associated shrubs such as Cytisus linifolius, Daphne gnidium, Ulex canthus and the endemic Lavendula stoechas (Lamiaceae). In associated large clearings Thymelaea lythroides and the conspicuous composite Ormenis multicaulis are usually common. Herbaceous vegetation is also largely confined to clearings and typically includes various bulbous plants like Asphodelus microcarpus, Dipcadi serotinum and Urginea maritima.

Southwestern Mediterranean Quercus suber Forest Forest dominated by Quercus suber occur, for example, on the Rif growing to an altitude of about 1200 m. They can reach a height of 15 m and have a dense sub-canopy layer reaching 5 m or so composed largely of Arbutus unedo and Erica arborea. A shrub layer of small shrubs like Cistus salviifolius and the endemic Lavendula stoechas (Lamiaceae) is often present. Clearings include various heliophilous shrubs such as Cistus populifolius and the endemic Halimium lasiocalycinum (Cistaceae).

Southwestern Mediterranean Olea europaea Thicket Thicket or scrub forest characterized by Olea europaea together with Chamaerops humilis, Pistacia atlantis and P. lentiscus may represent a natural climatic climax community in certain arid areas, but most stands now show evidence of human interference. Olea can grow into a small tree (10-12 m) but is often much smaller. These thickets would have occupied what is now much of the lowland cultivated areas, but they can also grow at altitudes up to about 1650 in the Grand Atlas. Associated species include Juniperus phoenicea and the endemic Argania spinosa (Sapotaceae). Some of the degraded vegetation in the lowland plains has now become dominated by Chamaerops humilis, but these have now become havens for geophytes such as Aceras, Allium, Anacamptis, Anthericum, Asphodelus, Bellevalia, Colchicum, Crocus, Dipcadi, Erythrostictus, Gagea, Gladiolus, Iris, Leucojum, Muscari, Narcissus, Ophrys, Orchis, Ornithogalum, Romulea, Scilla and Urginea. In spring these plains in Morocco turn into a multi-coloured garden with large patched of the orange endemic Calendula algeriensis (Asteraceae), blue patches of the endemic Convolvulus gharbensis (Convolvulaceae), mixed with purple Fedia, violet Linaria, yellow Chrysanthemum and Diplotaxis.

Southwestern Mediterranean Tetraclinis articulata Forest Apart from a small population in Malta and in the extreme southeastern corner of Spain, Tetraclinis articulata is confined to North Africa. Moroccan forests characterized by this species occur on the lower Mediterranean slopes of the Rif and then extend eastwards into Algeria. They also occur on the northern slopes and valleys of the Anti Atlas, Middle Atlas and High Atlas. Trees of Tetraclinis can reach heights of 15 m, but their narrow crowns form only a light canopy and so most associated species are heliophilous. The most common of these include Ebenus pinnata, Lavendula multifida, Teucrium polium, while less common are Ampelodesmus mauritanicum, Anthyllis cytisoides and the endemic Polygala balansae (Polygalaceae).

Copyright © 2010 Peter Martin Rhind Southwestern Mediterranean Cupressus atlantica Forest Forest dominated by the endemic Cupressus atlantica (Cupressaceae) form scattered stands between 1000-2000 m in the High Atlas. Some of the best examples form ‘islands’ within the Juniperus phoenicea zone. Cupressus atlantica can reach heights of 40 m or more but most of the remaining trees are much smaller than this.

Southwestern Mediterranean Juniperus phoenicea Forest Juniperus phoenicea forest has two principal habitats: coastal sands and high plateaus. On dunes they develop behind the first dune ridge where there is a degree of shelter from the maritime environment. Other characteristic species include Asparagus alhus, Clematis cirrhosa, Ephedra fragilis, Jasminium fruticans, Philyrea angustifolia, Pistacia lentiscus, Rhamnus alaternus and Smilax aspera. Inland forests occur on the Great, Middle and Anti- Atlas, but rarely exceed an altitude of more then 2200 m. At higher altitudes Juniperus phoenicea becomes mixed with J. thurifera, while associated species include Adenocarpus bacquei, Artemisia herba-alba, Buxus balearica, Carthamnus fruticosus, Fraxinus xanthoxyloides, Genista myriantha, Globularia alypum, Lavendula multifida, Rhamnus oleoides and Stipa tenacissima.

Southwestern Mediterranean Pinus halepensis Forest The only extensive stand of this forest in the southwest Mediterranean occurs above 1200 m in the High Atlas. Pinus halepensis usually forms and emergent tree reaching heights of 20 m, while lower canopy species usually include Quercus ilex and Tetraclinis articulata.

Southwestern Mediterranean Pinus pinaster Forest These forests occur between 1500-2200 m on northern slopes of the Middle Atlas and High Atlas and between 1000-1900 m in the western Rif.

Southwestern Mediterranean Cedrus atlantica Forest Forests dominated by the endemic Cedrus atlantica (Pinaceae) are confined to the mountains of Algeria and Morocco. This species of Cedrus can attain heights of 60 m and live for 750 years or more. In Algeria extensive stands occur in the Aurès, while in Morocco most is confined to the Middle and High Atlas. Its upper altitudinal limit is about 2800 m but its lower limit is less well defined due to human interference. Associated flora includes an interesting mix of Mediterranean and Eurosiberia elements. The latter include Carex verticillatum, Digitalis purpurea, Parnassia palustris, Pinquicula vulgaris, Primula vulgaris, Sanicula europaea, Viola palustris and the fern Osmunda regalis.

Southwestern Mediterranean Acacia-Argania Dry Woodland/Succulent Thicket Although mainly within the Morocco this vegetation also extends into the northwest corner of Western Sahara as well as the two easternmost Canary Islands of Fuerteventura and Lanzarote and numerous associated islets (e.g. Graciosa). On the African mainland it occupies the Atlantic coastal plain, the lowlands of Haouz-Tadla, the Souss and Draa Valleys, and the western end of the High and Anti-Atlas Mountains. Woodland dominated by the endemic Argania spinosa (Sapotaceae) and succulent shrubland dominated by species of Euphorbia are the predominant vegetation types. Argania is the only member of Sapotaceae found in mainland Africa north of the Sahara. The main associates include Acacia gummifera, Cytisus albidus, Ephedra altissima, Euphorbia officinarum, Launaea arborescens, Periploca laevigata, Rhus tripartitum, Senecio anthephorbium, Tetraclinis articulata, Warionia saharae and Withania frutescens. Other acacias such as Acacia raddiana and Acacia ehrebengiana are more prevalent in the inland areas but these are widely distributed throughout the Sahara Desert. In eastern parts Balanites aegyptiaca and Maerua crassifolia are common associates. Further inland, these woodlands merge into

Copyright © 2010 Peter Martin Rhind stands of succulent Euphorbia, which typically include three succulent and two dendroid species. With the exception of Euphorbia resinifera, they are best developed close to the sea where mists ameliorate the summer temperatures. Recently, a new subspecies of the Canarian Island’s Dracaena drago has been discovered which is associated with this vegetation on the African mainland named Dracaena drago subsp. ajgal. This relict species is restricted to a small area known as Massa River Canyon (in the Occidental Anti- Atlas) where several thousand of individuals have been recorded.

Southwestern Mediterranean Altimontane Shrublands Dwarf shrublands dominated by dense, cushion-shaped, spinous shrubs is one of the most widespread and characteristic vegetation types in the mountains of North Africa. In Morocco it represents the climatic climax from the tree line up to about 3900 m, and is well represented on the summits of the Middle Atlas and the Great Atlas, but in the Anti-Atlas it is only found on the massif of Siroua, and it is absent from the Rif, which is too low. In Algeria it is less common but can be seen on the summit of Aurès and the Djurdjura. The dominant species in Morocco are Alyssum spinosum, Amelanchier ovalis, Arenaria dyris, Berberis hispanica, Bupleurum spinosum, Cytisus balansae, Erinacea anthyllis, Juniperus communis, Lonicera pyrenaica, Rhamnus alpinus, Ribes alpinum and Vella mairei. There are also numerous endemic plants.

Further information required.

References

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