Calcium Determination.—Calcium carbonato, being an easily soluble compound, is always accessible to plants. Instead of laborious  Ca analyses, therefore, very simple carbonate determinations are performed. It must not be overlooked, however, that calcium may be present in the soil in other combinations than the carbonate and, furthermore, that in making the carbonate determinations other carbonates, as of magnesium and iron, are included in the results. The fact remains, however, that magnesium carbonate, present in large quantities in dolomite, closely resembles calcium carbonate in its effect upon vegetation. (Braun-Blanquet 1932:184-5)
Kürsteiner (1923) found considerable quantities of Bacterium mesentericus and other schizomycetes in primary erosion layers free of humus and in fine rock crevices of high alpine summits even at heights of 4,000 to 4,200 m. These minute organisms probably hasten chemical erosion by production of carbonic acid, H2CO3. Carbonates dissolve in the presence of carbonic acid, especially the widely distributed carbonates of calcium, magnesium and iron. Silicates of the alkahes and alkaline earths are decomposed by carbonic acid (Ramann, 1911, p. 28). Very succinct data on the importance of microorganisms in weathering and soil formation are found in the work of Wollny (1898). (Braun-Blanquet 1932:242)
BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.