The present study provides quantitative estimates of the vegetation structure and distribution of the plant communities in Tihamah coastal plains of Jazan region. The factors affecting the species distribution and the correlations between the vegetational gradients and the edaphic variables were discussed. Eight major community types constitute the major part of the natural vegetation of the study area and are dominated by nine perennials: Ziziphus spina-christi (L.) Willd, Calotropis procera (Wild) R. Br., Leptadenia pyrotechnica (Forssk.) Decne., Suaeda monoica Forssk., Panicum turgidum Forssk., Salvadora persica L., Acacia tortilis (Forssk) Hayne, Tamarix aphylla (L.) Karst. and Cyperus conglomeratus Rottb.
The results of this study confirm that the study area is a subtropical desert and belongs floristically to the Sudanian territory and also that therophytes are the most frequent life-form in this region.
Analysis of the correlation between the vegetational gradients and the edaphic factors showed that soil pH, moisture, electrical conductivity, organic carbon, calcium carbonate, bicarbonate, soil cations: sodium, potassium, calcium, and the sodium adsorption ratio are the main operating edaphic factors in the area.