The eastern scarp is an area of transition between the plateau and the Oued Cherrat, and it is characterised by slopes going from moderate to steep. The slope, the aspect, and the presence of water influence the vegetation, specifically for species’ distribution, density, vigour and cover. Natural, and artificial vegetation, is generally located on slopes and valley bottoms, while on the top of the hills, due to the shallow, poor, and rocky soil, vegetation is rarer, lower, and mainly composed of dwarf shrubs.
Quercus suber is rare in the scarp area because of the steep slopes and the not very deep soil; only in some parts, closer to the undulating area, sparse trees, relicts of the cork oak forest degraded by the utilisation and overgrazing can be present.
The most representative forest formation is the one with Tetraclinis articulata. This species is xerophile (Ionesco and Sauvage, 1962) and its requirements well fit the local environment; generally the vigour is good and regeneration by shoots is frequent. Tetraclinis articulata, also called Berbers’ thuya, has pluviometric factor (Q2) requirement between 40 and 80 and requires a warm and dry climate with a temperate winter. It grows on rocky soils, avoiding sandy and poorly drained soils; it is rather indifferent to chemical soil nature. The limiting factor of its distribution is mainly constituted by humidity. Generally it grows on limestone and it is substituted by cork oak on siliceous rocks (Ionesco and Sauvage, 1969).
The cover goes from 30 to 60%, the height is around 5m and the dense undergrowth is generally composed by medium to high shrubs as Pistacia lentiscus, Phillirea latifolia, Rhus pentaphilla, and Olea europaea var. oleaster. Moving toward the slope bottom, where the soil becomes clayey and the microclimate is more humid, the Berbers’ thuya is gradually substituted by high mediterranean shrubs like Olea oleaster, Phillirea latifolia, Pistacia lentiscus, and Myrtus communis (Table 23).
Tetraclinis forests are generally managed as coppice. The plant has an important socioal and economic value, its wood is much appreciated for local crafts.
Two kinds of artificial forest are present in this area: the Eucalyptus camaldulensis and the Pinus halepensis (Table 24).
Eucalyptus has been planted along the oued, where the valley bottom is flat; it is in good condition and generally managed as high forest.
Pinus halepensis plantation started about 20-25 years ago, in the limit between the eastern scarp area and the southern reliefs, where it is more abundant. It has been planted on terraces along the contour lines, on the slopes facing West or South, not on top of hills, neither in the valley bottoms. Also in this part of the scarp area, like in the Tetraclinis articulata formation, Mediterranean shrubs are abundant, dense and high in the northern aspect and in the valley bottom, where vegetation suffers less from drought. Generally the cover of Pinus halepensis is around 40%, the height is about 10m, with an open second layer of Cistus monspeliensis and sparse high shrubs of Pistacia lentiscus. The cover and the vigour of the trees are related to the slope, soil depth and aspect. Probably Aleppo pine was planted on eroded and degraded areas, for soil conservation, but some of these plantations (20%) failed and others are very precarious; this situation could be due to the excessive slope and to the severe erosion. Failed pine afforestation land is mainly characterised by bare soil and gully erosion.
The aspect could be considered as another important factor of afforestation failure; generally in the slopes facing South, the cover is composed by Cistus monspeliensis, while, to avoid dry conditions, pine is located along the incisions together with Pistacia lentiscus. Grazing is not a major problem in the scarp area, because most of it is difficult to reach because of the steepness. Wood collection is frequent and, except for the eucalyptus plantation, is done only by local people for fuel wood and tool making.