Vegetation-soil relationships in Tihamah coastal plains of Jazan region, Saudi Arabia

The present study provides quantitative estimates of the vegetation structure and distribution of the plant communities in Tihamah coastal plains of Jazan region in relation to the soil properties. The factors affecting the species distribution and correlation between the vegetational gradients and the edaphic variables are 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, Calotropis procera, Leptadenia pyrotechnica, Suaeda monoica, Panicum turgidum, Salvadora persica, Acacia tortilis, Tamarix mannifera and Cyperus conglomeratus. The results of this study confirm that the study area is a tropical desert and belongs floristically to the Sudan territory and also that therophytes are the most frequent life-form in the communities. Analysis of the correlation between the vegetational gradients and the edaphic factors show that soil pH, moisture, electric 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