Bayreuther Institut für Terrestrische Ökosystemforschung
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Effects of decreasing SO42-, Ca2+, and Mg2+ deposition on the cation exchange capacity and the base saturation of acid forest soils


From 01/1995 to 12/1997

Principal Investigator: Egbert Matzner
Staff: Gunda Matschonat
Grant: 0339476 B Vorhersage und Erklärung des Verhaltens und der Belastbarkeit von Ökosystemen unter veränderten Umweltbedingungen

The acidity of rain and also the input of base cations with dust diminishes. Resulting changes in soil solution pH, ionic strength, and single cation acitivities will influence the charge characteristics, the base saturation of the exchange complex and the solution composition. Changes in sulphate concentration significantly influenced the CEC only in some samples, while variation in both pH (0.2 - 0.5 units) and ionic strength (halved or doubled) were important and resulted in changes in the CEC of up to 65% of the original value. As the effects of increasing pH and decreasing ionic strength on CEC are antagonistic, a decrease in acid deposition will not inevitably increase the CEC, but the effects may balance each other in some soils. Equilibrium calculations predict an increase in the fraction of trivalent cations in solution and a decrease in the monovalent fraction as the sum of cationic charge in solution increases. We demonstrated that this pattern of cations may be observed in field data. An increase in base saturation will probably not take place as deposition diminishes because small cation concentrations in solution tend to lower the base saturation. On the other hand, a small sum of cationic charge in solution supports low Al concentrations and higher pH and Ca/Al ratios. Comparing disturbed and undisturbed samples from different soils we found the quality of the soil solution with respect to pH and Ca/Al molar ratios to be better, equal to or worse than that of the bulk soil. Thus, a previously suggested general pattern of less favorable conditions in soil soltutions from undistrubed samples was not confirmed. (final report 1998)

List of publications of this Project

Matschonat, G; Vogt, R: Significance of the total cation concentration in acid forest soils for the solution composition and the saturation of exchange sites, Geoderma, 84, 289-307 (1998) -- Details
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) -- Details
Matschonat, G; Vogt, R: Assessment of a laboratory method to obtain the equilibrium solution composition of forest soils, European Journal of Soil Science, 48, 545-552 (1997) -- Details
Vogt, R; Matschonat, G: Patterns of soil solution composition in acid forest soils: differences between undisturbed and bulk samples, Z. Pflanzenernährung Bodenkunde, 160, 549-554 (1997) -- Details
Matschonat, G; Matzner, E: Soil chemical properties affecting NH4+ sorption in forest soils, Z. Pflanzenernährung Bodenkunde, 159, 505-511 (1996)
Matschonat, G; Vogt, R: Equilibrium solution composition and exchange properties of disturbed and undisturbed soil samples from an acid forest soil, Plant and Soil, 183, 171-179 (1996) -- Details
Holland, W; Matschonat, G; Grosholz, C: Entwicklung der Basensättigung und der Kationenaustauschkapazität des Bodens bei nachlassenden Säure-Einträgen, Mitteilungen der Deutschen Bodenkundlichen Gesellschaft, 76/I, 297-298 (1995)
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