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Because of its powerful rooting system, Atlas pistachio tree plays an important role against soil erosion and desertification which constantly threatens the arid and Saharan regions. In this work, the variation of mycorrhization parameters (mycorrhizal rate, colonization intensity, arbuscular and vesicular content) are studied according to the seasonal and bioclimates variation, in order to understand the best conditions for the establishment of the symbiosis in this species. The physicochemical properties of soils (pH, electric conductivity, organic matter and total limestone amount) were determined for five sampling sites. Spores harvested fungi from the rhizosphere area were morphologically identified, and the specific diversity of mycorrhizal fungi was measured in the different sites. Microscopic observations of the roots revealed the presence of arbuscular mycorrhizal fungi (AMF). The frequency of mycorrhization and the intensity of colonization are higher in the arid bioclimate, characterized by alkaline soils, low organic matter with relatively low levels of calcium carbonates. A total of 19 species of mycorrhizal fungi has been isolated. This set is dominated by two families (Gigasporaceae and Glomeraceae) but the most common genus is Gigaspora. Analysis of Variance (bioclimate factor and bioclimate x season interaction) showed a very significant difference for the frequency of mycorrhization and highly significant difference for soil variables. The Fisher (LSD) test revealed the presence of heterogeneous groups for all studied parameters except for the vesicle amount. PCA, as well, showed an aridity gradient on the first axis and a thermic gradient on the second one.