Experimental investigation of drought induced acidification in a rich fen soil

Intact rich fen soil cores with controlled water levels near thesurface were installed in an open greenhouse. To simulate short termsummer drought, water levels were lowered (20 cm) after two weeks inhalf of the cores (experimental cores) and remained near the surface inthe other half (blanks). After two more weeks, the water levels werebrought back to the surface in the experimental cores and remainedthere for another two weeks. In the blanks, reduction and alkalinizationof the top peat layer occurred. In the experimental soil cores oxidationand acidification started within one week after drawdown. An indicationfor a drought induced rise in soluble reactive phosphorus has beenfound. The velocity of the acidification process illustrates the dynamicnature of the hydrochemical conditions in fen soils during drought. Theprocesses controlling the acid/base status of rich fen, the effect ofdrought induced acidification on P availability and the significance forthe vegetation are discussed.