Birch encroachment affects the base cation chemistry in a restored bog

Wertebach T-M., Hölzel N., Kleinebecker T.

Zusammenfassung

In this study, we compared non-forested and forested habitat types of a degraded bog in Western Germany with regard to the base cation chemistry of their pore waters. Peat profiles were sampled in 10-cm intervals every month from April to July 2009 down to a maximal depth of 150cm. Pore waters were analysed for Ca, Mg, K and Na concentrations. Additionally, electrical conductivity and pH were measured in surface pools. Both habitat types were sampled with four replicate plots, showing the same vegetation structure. Strong differences were found between the concentrations and distributions of base cations in the pore water profiles from the different habitat types. The forested sites revealed higher concentrations for all base cations, but especially for Ca and Mg. Seasonality had an effect on element distributions in pore waters, but its influence was particularly strong at the forested sites. Element distributions and seasonality were caused by several interacting biological and physicochemical processes, such as plant uptake and mineralization or evaporative enrichment and dilution by rainwater. Concludingly, we draw implications for bog restoration and for the use of element ratios as criterion of mineral influence on bog waters. Our study clearly demonstrates the enhancement of base cation supply by birch encroachment, which is posing an additional burden on successful bog restoration. Additionally, the importance of an intact buffer zone around restored peat bogs is underlined. © 2013 John Wiley & Sons, Ltd.