Natural ecosystems in the face of climatic fluctuations

The depressions centered on the northeast of the western Mediterranean have a negative influence on rainfall in Oranien since their action results in a drought in the west. The matorrals located on the mountainous massifs of northwestern Orania with the steppes of western Algeria (Beni-Saf Sidi Djilali Sebdou El-Bayadh El-Aricha Mecheria El-Kreider etc. ...) have been strongly marked by drought. Relying mainly on climatic data bioclimatic syntheses (Thermal amplitude xerothermic index De Martonne index umbrothermal diagrams of Bagnouls and Gaussen and the Q2 of Emberger) which advocate the often regressive dynamics of these plant formations quite degraded Through the results the author shows that the cold thermal variants favor the contact between the woody formations and the steppe formations with thermal determinism (formations with thorny xerophytes in cushions most often). The therophytic biological type seems to dominate in all the explored areas and their percentage can reach sometimes 48%.