Effects of liming on shallow acidified moorland pools: A culture and a seed bank experiment

To study the effects of liming on water chemistry and the development of aquatic macrophytes, culture experiments with Littorella uniflora (L.) Aschers. and Juncus bulbosus L. were carried out. The addition of powdered limestone to acidified moorland pools led to increased phosphate levels in the water layer and increased carbon dioxide levels in the sediment pore water and the water column; this resulted in an excessive growth of Juncus bulbosus. Similar observations were made in seed bank experiments, conducted in a greenhouse. After 2 years the abundance of J. bulbosus was very high. Littorella uniflora and Lobelia dortmanna L. germinated spontaneously and developed in mini-ecosystems with sediments from the Padvindersven and the Peetersven, respectively, two moorland pools from which these species had disappeared a few decades ago, Spontaneous germination and development of endangered soft water macrophytes only occurred on sediments after removal of the organic sapropelium layer. Therefore, this study showed that in order to restore the original water chemistry of acidified moorland pools, removal of the organic sapropelium layer is necessary, as well for improving vegetation development.