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| Matschonat, G; Vogt, R: Effects of changes in pH, ionic strength, and sulphate concentration on the CEC of temperate acid forest soils, European Journal of Soil Science, 48, 163-171 (1997) | |
Abstract:
As the acidity of rain diminishes, changes in the pH, ionic strength, and ion activities of the soil
solution will influence the charge characteristics of soil. We have investigated the response of
cation exchange capacity (CEC) of three acid forest soils of variable charge to small changes in pH,
ionic strength, and SO:- concentration. The variable charge for these temperate soils has the same
significance as for tropical soils and those from volcanic ash. Maximum absolute increase in CEC
on increasing pH by 0.2-0.5 units reached 5 cmol, kg-' in 0 horizons. The increase in CEC on
doubling ionic strength in EA and Bsh horizons of a Cambic Podzol was about half that amount,
but relative gains compared to effective CEC were 65 and 46%, respectively. For other soil
horizons, absolute changes were smaller, and relative changes were between 10 and 30%. Halving
the SO:- concentration significantly influenced CEC only in some samples. Both pH and ionic
strength must be adjusted with care when determining CEC, of acid forest soils. Decreasing acid
deposition will not inevitably increase CEC, , because in some soils pH effects may be balanced by
simultaneous decrease in ionic strength. |
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