The study aims to define the phytosociological units in which the vegetation formations of Djebel Medjounes are grouped, to monitor their dynamics, and to determine the climatic and edaphic conditions in which they develop. The methodology used is called "phytosociological" or "sigmatist".The methodology allowed for the individualization of thirteen associations and three sub-associations belonging to 4 classes, 6 orders, and 10 alliances. The Quercetea ilicis class is represented by five associations affiliated with the Quercetalia ilicis order, and incorporated into a single alliance, the Quercion ilicis. The association of Pistacio- Quercetum ilicis Brullo, Martino & Marceno 1985, and four other associations (Calicotomo spinosae-Quercetum rotundifoliae Dahmani-Megrerouche & Loisel ex Meddour, Meddour Sahar, Zeraia & Mucina, (2017), Genisto tricuspidatae-Calicotometum spinosi ass, nova Meddour, (2010), Calicotome spinosae-Thymuteum ciliatus nouv, Rhamnus alaternus Boulaacheb et al, (2005)) are integrated into the Pistacio-Rhamnetalia order and the alliance of Genisto tricuspidatae- Calicotomion spinosi;The Rosmarinetea officinalis class has three associations, the Bupleuro spinosi-Astragaletum amartus (Quézel, 1975) association belonging to the order of Erinaceetalia anthyllidis and the alliance of Festusion algeriensis, bringing together xerophytic spiny groups and mountain-Mediterranean and supra-Mediterranean meadows. Two associations; Centaureo acaulis - Genistetum tricuspidata nov and Helianthemo cinereum subsp. rotundifolium - Genistetum tricuspidata nouv are affiliated with the order of Cisto mauritanici-Thymetalia munbyani and the alliance of Genisto atlanticae-cistion villosi; the Lygeo-stipetea class includes four associations integrated into the order of Lygeo-stipetalia.The association of Plantago coronopus and Helianthemum apenninum belonging to the alliance of Stipo-Launaeion acanthocladae; the association of Artemisietum herba-albae Maire, (1926) affiliated with the alliance of Noaeo mucronatae-Artemision herba-albae; the association of Plantago lagopus L. and Pseudopodospermum undulatum (Vahl) Zaika, Sukhor. & Kilian, ranges in the alliance of Artemisia herba-alba and Plantago lagopus; the association of Artemisia herba-alba Asso and Launaea lanifera Pau, integrated into the alliance of Artemisia herba-alba and Poa bulbosa; Class of Tuberarietea guttatae with a single association of Filago pyramidatae-Plantaginetum lagopi (nov. ass) observed by Dahmani (1997), belonging to the order of Brachypodietalia (Trachynietalia) distachyae and the alliance of Thero-Brachypodion.Based on 237 phytosociological surveys, we recorded 420 taxa belonging to 53 families and 226 genera. The flora consists of 186 therophytes (45.03%), 133 hemicryptophytes (32.20%), 33 geophytes (8%), 40 chamaephytes (9.68%), and 22 nanophanerophytes, which make up 5.30% of the floristic assemblage. From a phytogeographic standpoint, the Mediterranean element is relatively dominant with 183 species (45%). There were forty endemic species present, accounting for 9.82%.The studied vegetation formations (scrublands, heathlands, grasslands, and steppes) are mainly determined by climatic factors (precipitation, temperature). Based on our analysis, we observed significant degradation and substantial regressive dynamics. To establish a phytosociological map, we used Landsat satellite images from 1989, 2000, 2009, and 2020, as well as data from a digital terrain model (DTM) to create geomorphological, hypsometric, slope, and exposure maps. To assess the impact of drought (SPEI) on vegetation cover between 1989 and 2020, we combined NDVI and NDWI-Gao. Our method for detecting changes in vegetation cover consists of comparing the distributions of NDWI and NDVI values for each year in different phytosociological associations. Environmental factors, particularly climatic factors, play a crucial role in the development and distribution of species.