Sclerophyll

Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves, short internodes (the distance between leaves along the stem) and leaf orientation which is parallel or oblique to direct sunlight.

Sclerophyllous plants occur in many parts of the world, but are most typical of areas with low rainfall or seasonal droughts, such as Australia, Africa, and western North and South America. They are prominent throughout Australia, parts of Argentina, the Cerrado biogeographic region of Bolivia, Paraguay and Brazil, and in the Mediterranean biomes that cover the Mediterranean Basin, California, Chile, and the Cape Province of South Africa.

In the Mediterranean basin, holm oak, cork oak and olives are typical hardwood trees. In addition, there are several species of pine under the trees in the vegetation zone. The shrub layer contains numerous herbs such as rosemary, thyme and lavender. In relation to the potential natural vegetation, around 2% of the Earth's land surface is covered by sclerophyll woodlands, and a total of 10% of all plant species on Earth live there.

The word comes from the Greek sklēros (hard) and phyllon (leaf). The term was coined by Andreas Franz Wilhelm Schimper in 1898 (translated in 1903), originally as a synonym of xeromorph, but the two words were later differentiated.

Sclerophyll woody plants are characterized by their relatively small, stiff, leathery and long-lasting leaves. The sclerophyll vegetation is the result of an adaptation of the flora to the summer dry period of a Mediterranean-type climate.

Plant species with this type of adaptation tend to be evergreen with great longevity, slow growth and with no loss of leaves during the unfavorable season. As a result, the thickets that make up these ecosystems are of the persistent evergreen type, in addition to the predominance of plants, even herbaceous ones, with "hard" leaves, which are covered by a thick leathery layer called the cuticle, that prevents water loss during the dry season. The aerial and underground structures of these plants are modified to make up for water shortages that may affect their survival.

The name sclerophyll derives from the highly developed sclerenchyma from the plant, which is responsible for the hardness or stiffness of the leaves. This structure of the leaves inhibits transpiration and thus prevents major water losses during the dry season. Most of the plant species in the sclerophyll zone are not only insensitive to summer drought, they have also used various strategies to adapt to frequent wildfires, heavy rainfall and nutrient deficiencies.

The type of sclerophyllic trees in the Palearctic flora region include the holm oak (Quercus ilex), myrtle (Myrtus communis), strawberry tree (Arbutus unedo), wild olive (Olea europaea), laurel (Laurus nobilis), mock privet (Phillyrea latifolia), the Italian buckthorn (Rhamnus alaternus), etc.