The cation cycle
• Cycling of cations is not a completely closed cycle in natural ecosystems. Especially dissolved organic carbon (DOC) and strong acids which are produced anthropo-genically displace cations within the soil horizons or this leads to loss of cations to the groundwater.
• Cation losses lead to acidification of soils, when the losses are not compensated by weathering of primary minerals or by import of dust, or by liming operations.
In an ecosystem, the turnover of Ca is larger than that of K, and both exceed that of Mg.
Base saturation determines the type and availability of the various N types (amino acids, ammonium, nitrate). Lateral transport of cations, together with the transport of DOC, explains the differentiation of soil chemical characteristics and of vegetation even along short hydrolo-gical gradients.
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