The influence of lithology, relief and exposure on the soil and vegetation of the arid region of eastern Samaria.

Abstract

A small complex area in the Samarian Desert was investigated. The rainfall reaches about 250 mm. The area consists of a hill where limestone, chalks, marls and nari crust are exposed. Various young sediments are also present. Mediterranean batha vegetation characterizes the Terra rossa and dark Rendzina soils that cover hard rocks on northern and western slopes. Irano-Turanian vegetation (mainly Noaea mucronata ) covers the Rendzinic Desert Lithosol that has developed from hard chalk on the southern slopes. At the same exposure Saharo-Arabian vegetation (mainly Fagonia mollis and Blepharis ciliaris ) characterizes the soft chalk that is covered by calcareous desert Lithosols. Almost no vegetation was found on marl with a marly desert Lithosol soil cover; only toward the margins is there some cover of Salsola vermiculata. The vegetation on natric Grumic Serozems that developed from clay sediments is restricted to favored spots, like hollows, cracks etc., that receive higher amounts of water. These spots are also relatively leached. A close relationship was found between vegetation characteristics and degree of soil leaching: vegetation diversity and density decrease with the increase of the Exchangeable Sodium Percentage, Sodium Adsorption Ratio and salinity (Electrical Conductivity) values. The same is true with respect to lime content of soils on hard rocks. The reason for these relationships is attributed to different moisture regimes.