The hydrology as related to topographical differences in height of an area differing little in parent material, can be considered to be an independent factor determining the spatial variation in soil and vegetation. Groundwater hydrochemically can be related to its residence time in the subsoil using the ionic ratio (Ca2+/(Ca2+ + Mg2+ + K+ + Na+)) and the electric conductivity as indicators, both increasing with growing residence time and of which ionic ratio may reach 0.90. This latter phenomenon could be related to the weathering of calcite bearing sediments. Considerable regional differences are met with depending on initial PCO2 in infiltration areas and on differences in calcite content of the parent material. By its dominating presence in areas with a positive net subsurface inflow, the Ca2+-ion also is the dominating cation on the exchange complex and it can be considered as the antagonist of the H+-ion on the cation exchange complex and hence as a regulator of soil acidity. Indirectly the Ca2+-ion interferes with pH-dependent microbial processes as nitrification and with phosphate solubility. Regarding nutrient availability, the role of the Ca2+-ion in determining ecological states is obvious.