Mediterranean-Climate Forests

In the hot-temperate zones, where hot, dry summers alternate with a damper cold season, vegetation consists of forests, maquis (thick, scrubby underbrush), and garigues (low, open scrublands) of evergreen broad-leaved species that may in some areas be associated with conifers. These species have small, coriaceous leaves—hence the name sclerophyll — that developed this mechanism for adapting to the dry summers.

Whereas the sclerophyllous forests are climax formations (equilibrium status of an organism's community which remains stable until the environmental conditions do not change remarkably), the maquis and garigue are the secondary results of repeated exploitation. The maquis typical of siliceous soil is a stand of xerophilous and sclerophyllous evergreen trees and shrubs that is sometimes so dense as to be impenetrable. It can attain heights of 3 meters and comprises species that belong to the undergrowth and the open spaces of primary forests.

The garigue (or medium or low matorral) that grows on limestone gets its name from the Castilian garric, which is used for the kermes oak (Quercus coccifera) and does not exceed 2 meters in height.

The Mediterranean sclerophylls may be associated with conifers that are generally localized. In some cases they represent a climax stage, whereas in others they were planted by humans. In Europe the sclerophyllous forests are typical of the Mediterranean coasts, Portugal, central-southern Spain, and Crimea; in the Americas they are found in California, Mexico, and central coastal Chile; in Africa in Morocco, Algeria, Tunisia, coastal Libya, and South Africa (Cape region); and in the southern part of the Australian continent.

On the best lands in the Mediterranean region, zonal vegetation has been replaced by crops, primarily olives and grapes, so it is now confined to marginal environments with almost always superficial soil. In Europe one must distinguish the coastal from the subcoastal and Mediterranean mountain forests. Along the northern shores of the Mediterranean, evergreen oak (Quercus ilex) formations are the most typical.

These can reach heights of 15 meters, and in areas with noncalcareous substrata they are replaced by cork trees (Quercus suber). The species in the shrub layer (Viburnum tinus (laurustinus), Phillyrea latifolia (tree phil- lyrea), and Phyllyrea angustifolia (narrow-leaved phillyrea), Pistacia lentiscus (mastic-tree), and Pistacia terebinthus (turpentine tree), Rhamnus alaternus (buckthorn), Rosa sempervirens (evergreen rose), Buxus sempervirens (common box), and vines such as Smilax aspera, Clematisflammula (plume clematis), and Lonicera sp. pi. (honeysuckle) grow to heights of 3-5 meters.

In the warmer areas evergreen oak grows on the mountain plain, whereas along the coast it is superseded by wild olive (Olea oleaster), carob (Cemtonia siliqua), and dwarf fan-palm (Chamaerops humilis). Nearly all the Mediterranean regions are mountainous, and, therefore, above certain altitudes typical Mediterranean vegetation is replaced by deciduous or mixed forests where pubescent oak (Quercus pubescens) is found.

In Africa there is a northern section where evergreen oak groves alternate with maquis and a southern section. On the Atlantic coasts typical Mediterranean vegetation is flanked with an almost aphyllous (without leaves) cypress, African thuya (Tetraclinis articolata). The innermost and highest Atlantic sector along the slopes of the Haut and Moyen Atlas Mountains is colonized by evergreen oak and Spanish juniper (Juniperus thuripherea); the southern mountains, between 1,300 and 2,000 meters above sea level, are characterized by open formations of Cupressus atlantica or Spanish fir (Abies pinsapo) or atlas cedar (Cedrus atlantica).

Mediterranean vegetation in southern Africa is limited to the southern slopes of the Karoo mountain chain, which protect it from the effects of the continental climate. It comprises small groupings of trees or maquis and high garigues that differ floristically from those of northern Africa and present species of the genera Olea (olive), Gnidia (gnidie), Leucadendron, Berzelia, Agathosma, Cliffortia, Cussonia, and Protea—this last species is designated as "tall heather.”

In California sclerophylls are limited to a narrow coastal strip that is rich in species known as "chaparral," comprising shrub species of the genera Quercus (oak) and Arbutus (strawberry-tree), Ceanothus (ceano- thus), Arctostaphylos (bearberry), and a rosacea (belonging to the rose family) with needle-shaped leaves, Adenostoma fasciculatum.

From the physiognomical standpoint chaparral corresponds to the Mediterranean maquis, but unlike its counterpart it is affected by periodic outbreaks of fires caused by lightning. It includes scattered trees such as conifers and evergreen oaks that acquire a shrublike appearance in the driest stations. Similar types of vegetation can be found along the Chilean coast.

In Asia evergreen oak is found only in some stations in northern Turkey; the coastal forests consist of wild olive (Olea oleaster) and carob trees (Ceratonia siliqua), whereas the subcoastal forests comprise kermes oak (Quercus coccifera) known as calabrian pine (Pinus brutia) and greek juniper (Juniperus excelsa).

Up to an altitude of 2,200 meters along the southern mountain slopes are found associations with black pine (Pinus nigra ssp. Palladium), cedar of Lebanon (Cedrus libani), Cilician fir (Abies cilicica), Greek juniper (Juniperus excelsa), Calabrian pine (Pinus brutia), yew (Taxus baccata), kermes oak (Quercus coccifera), aleppo oak (Quercus infectoria), and Lebanon oak (Quercus libani) in various groupings in the single locations. Maquis of Pistacia palestinica and Quercus calliprinos dominate the Palestinian and Lebanese coasts.

In southwestern, south-central, and southeastern Australia, the sclerophyllous formations are similar to those of the Northern Hemisphere's Mediterranean forests, even though their systematic origins are different. Locally the maquis is known as "malle-scrub": It is dominated by species of Eucalyptus (gum) associated with Acacia (acacia), Malaleuca, Pimelea (rice-flower), Chorizema, Baronia, Leptaspermium, and Pittosporum (klebsane) with manifest blossoms.

Where humidity levels are lower, vegetation takes on the form of maquis that can reach a height of 3 meters, and in areas where precipitation ranges from 750 to 1,500 millimeters, eucalyptus trees are associated with plants of casuarinas (Casuarina).

On the whole, temperate forests cover 2 billion hectares distributed over the continents: 41 percent are found in Russia, 32 percent in North America, 10 percent in northern Asia, 8 percent in Europe, 2 percent in Latin America, and the remaining 7 percent in Australia, New Zealand, and South Africa. The forest cover in these countries varies considerably, and one can say that temperate forests are disappearing in the southern parts of the world due to intensified exploitation for wood harvesting and that they are extending in the North as a result of the abandonment of farmlands and reforestation programs.