The aim of the present study aims to establish the impact of different restoration techniques (soil and vegetation works) of five pioneer species of the Doui Thabet forest (Mounts of Saida, West of Algeria): Pinus halepensis, Pistacia lentiscus., Tetraclinis articulata, Juniperus oxycedru,. and Stipa capensis (= S. tenacissima L.) between 2018 and 2020. An experimental field device covering an area of 1 ha has been installed in the Doui Thabet forest in a Pinus halepensis massive more than 80 years old. The following work was carried out: mechanical grinding of the vegetation (chopping), turning (scarification of soil) to a depth of 10 cm, tillage (Deep ploughing) to a depth of 20 cm, controlled burning of branches, clearing of Stipa capensis, seedlings planted in different seasons for certain species (Stipa capensis = S. tenacissima L.), monitoring of stump rejections and natural sowing. The sowing result varies according to the species and restoration techniques, it is high for Pinus halepensis and Stipa capensis. It is low for Tetraclinis articulata and Juniperus oxycedrus and none for Pistacia lentiscus while for Stipa capensis it is quite high when planted in autumn compared to spring. Turning and burning have proven to be the most abundant treatments for regeneration and growth. Grinding has medium seedling density and growth, while deep tillage and natural sowing showed low seedling density and growth.

A regional floristic and phytogeographic study was conducted in the Mounts of Saida, a subsector of the Tell Atlas (Oran) (O3), in the western Algeria. On an area of 56.31 Km 2 surveyed regularly over time during the springs and autumns from 2017 to 2019. A total of 344 taxa divided into 77 families and 223 genera, including 18 new (exogenous) for Tell Atlas (Oran) sub-sector (O3), have been inventoried. Of these 18 species, 8 belong to the phytogeographic areas of the arid (H) and hyperarid (AS) regions and 2 invasive species that reinforce and confirm theories of plant dispersal to the north and to high altitudes for adapting to climate change. The Factor Analysis of Correspondences (F.A.C) shows that species distribution is the result of local microclimates associated with the elevation; particularly, the mountains facing north receive a significant amount of humidity from the Mediterranean Sea.

Juniperus oxycedrus L. and Pistacia lentiscus L. are two taxa with a rigid or rigid enough structure caused by a solid pericarp resulting in a strong inhibition of the germination. The objective of this work was to test the effectiveness of certain pre-germinative treatments on the germination rate of the Juniperus oxycedrus and Pistacia lentiscus seeds with the aim of restoring perturbed ecosystems. In this context 180 seeds from each of the 2 examined species were tested in the laboratory (the number of repetitions is 5, to reach the degree of freedom 'ddl'). The seeds were divided into 4 groups of 20 seeds of each species and were treated as follows: 1) Immersion in the concentrated (95%) sulphuric acid (H2SO4) for 10, 30 and 60 minutes; 2) Mechanical scarification with a scalpel; 3) Soaking in hot water (at 100°C) for 30 seconds, 60 seconds and 2 minutes; 4) Cold stratification at 5°C for 24 hours. There is also a control group of 20 seeds representing each of the two species, which remained neutral. In the case of the Juniperus oxycedrus seeds the results showed that the germination rate improves after the mechanical scarification with a scalpel (92%), followed by the cold stratification with water (86%) and a treatment with a concentrated sulphuric acid for 60 minutes (82%). The seeds were treated with H2SO4 for 10 and 30 minutes, respectively, soaked in hot water; the control lot did not germinate. The germination rate for the Pistacia lentiscus seeds is 88% after the mechanical scarification and 84% after the cold water stratification. On the other hand, the treatment with H2SO4 or after soaking in hot water does not allow for the germination of these seeds. The same result is observed on the control group (0% for 30 days).

The forest of Doui Thabet is one of the forests of the Mounts of Saida (Western Algeria) which is experiencing a dynamic regressive. Located in the semi-arid bioclimatic stage, it is located at the edge of two phytogeographic sub-sectors: atlas Tellien Oranais (O3) and high plateau subsector (H1). Among the factors that threaten to curb this fragile and weakened ecosystem, in addition to drought and climate aridity and which has become a structural ecological phenomenon; the overgrazing is also a major limiting factor. This current study provides a qualitative and quantitative assessment of anthropogenic pressure exerted in this area zone. The methodology adopted in this study is that of Le Houerou (1969) and Montoya (1983), which it is based on the calculation of the annual needs of the herd in forage units, the estimate of the feed potential of production, the coefficient of overgrazing and in addition to the anthropogenic pressure index. The result of the forage balance in the forest rangelands of the studied area has a forage deficit (overload) of (96.64%) (a sylvopastoral imbalance), in addition to that, the coefficient of overgrazing is (92.3%) and the anthropogenic pressure index is very high (28). The conservation and the restoration of this area is a major concern in the face of global changes, taking into account their mode of reproduction and their dynamics, for the development of restoration strategies and more effective ways of protection.

Soil water erosion is a major aspect of landscape degradation in sub-wet to semi-arid Mediterranean environments. This problem has not been dealt with in detail in Algeria although it affects large areas. The objective of this study is to develop a methodology using remote sensing, the digital terrain model (DTM) and geographic information systems (GIS) to map areas with a risk of water erosion within the territory of Saida province and to produce a risk map that can be used as a reference document by the local authority. The presented methodology consists to incorporate three factors controlling the erosion: slope, material friability and land use. The resulting erosion risk map shows five areas of vulnerability to water erosion: very low, low, moderate, high and very high. Areas with high and very high risk of erosion cover more than 20% of the mountainous area and are consistent with our field observations. The methodology presented in this study can be generalized to all areas of the foothills of the Tellian Atlas, where erosion risks pose a threat to urban areas. This model is a tool to help implement a soil conservation plan in order to organise the measures to be applied and ensure sustainable soil management.