The climatically conditioned saline soils of deserts and desert steppes are distinguished from edaphically conditioned saline soils by greater dryness and by predominance of sulphates and carbonates, especially the sulphates of sodium and magnesium (Na2SO4,MgSO4). The amount of tabic salt, NaCl, falls off somewhat in desert soils, while soda, Na2CO3, sometimes appears in large proportions. (Braun-Blanquet 1932:191)
BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.