The effects of liming and reacidification on the growth of Juncus bulbosus: a mesocosm experiment

The growth of J. bulbosus was investigated in a cultivation experiment with a two-way factorial design for liming and reacidification. The growth of J . bulbosus on limed sediment in a reacidified water layer clearly differed from the growth in the other treatments. Dry weight was approximately five times higher after a growth period of five months which was the result of m ore rapid shoot growth and a higher production of rosette-bearing segments. Enhanced growth of J. bulbosus corresponded with increased concentrations of ammonium in the sediment pore water and increased carbon dioxide concent rations in the water layer. It is concluded that J. bulbosus benefits from higher nutrient concentrations in limed sediment when the carbon dioxide co ncentration in the water layer is relatively high. This occurs after reacid ification of the water layer when the bicarbonate-carbon dioxide equilibriu m is shifted towards carbon dioxide. As regular liming leads to accumulatio n of calcium carbonate in the sediment, it is to be expected that enhanced growth of J. bulbosus will continue in reacidifying Limed lakes in the futu re. (C) 1999 Elsevier Science B.V. All rights reserved.