EDAPHIC OR SOIL FACTORS: CHEMICAL 185 



Ca analyses, therefore, very siinplt> 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. 



Simple, calibrated calcimeters are commercially available in 

 various finishes, makes, and sizes. In Switzerland and in Germany the 

 calcimeter of Passon is most used; for soils poor in carbonate the small, 

 and for those rich in carbonate (more than 1 per cent) the large, 

 Passon apparatus is recommended. 



An estimate of the lime content of a soil may be obtained by wetting 

 a fresh soil sample with a few drops of dilute hydrochloric acid (HCl : 

 H2O = 1:1). Soils with less than 1 per cent of CaCOa cause no bub- 

 bling, those with 1 to 4 per cent effervesce weakly and for a short time, 

 while soils of more than 5 per cent effervesce strongly and for some 

 time. 



Instructions for the determination of the calcium content as 

 calcium oxide, CaO, are given by Wiegner (1926) and by Mitscherlich 

 (1923). 



Gypsum Vegetation. — Gypsum, CaSOi + 2H2O, and its anhydrite 

 (CaS04) bear exclusively calciphilous flora; the Ca ion here proves its 

 effectiveness. Fossil gypsum deposits of Paleozoic and Tertiary origin 

 exist in southern Europe in the Alps, in central and northern Germany, 

 northern France, Poland, and in numerous other places. The gypsum 

 islands of the Alps with their blinding brilliancy contrast sharply with 

 the adjoining sedimentary strata. Their vegetation is exceedingly 

 meager and consists of basophilous prostrate pioneer shrubs (Dryas, 

 Saliz serpyllifoUa) , a small number of pronouncedly lime-constant and 

 lime-loving species, and a few indifferent species. Gypsum-constant, 

 or even merely gypsum-loving, species are missing here, as they also 

 are in the steppe associations of Stipa capillata and of Carex humilis 

 and Inula ensifolia on the gypsum soils in the high plateau of Little 

 Poland examined by Dziubaltowski (1915, 1925) and Kozlowska (1925). 

 These gypsum soils are rather rich in carbonates; their H ion concentra- 

 tion varies between pH 7.6 and 6.8. However, the same associations 

 are found on calcareous loess. From the soil analyses of Miklaszewski 

 (cited in Dziubaltowski, 1925) it follows, incidentally, that the gypsum 

 bed rock contains no CaCOs, while in weathered gypsum rock 10 per 

 cent or more of CaCOs may be present. 



