Chemical characteristics of soils and pore waters of three wetland sites dominated by Phragmites australis:: relation to vegetation composition and reed performance

Chemical characteristics of soils and soil pore waters, plant species composition and horizontal stand structure were investigated for three reed stands in the Trebon Basin (Czech Republic): Branna sand pit and two littoral stands of Rozmberk fishpond (Rozmberk East and Rozmberk West). Phragmites stands were expanding, stable and retreating at the three sites, respectively. The elemental soil composition (especially of C, N, P, and K) indicated the lowest trophic conditions at Branna, intermediate at Rozmberk East and the highest at Rozmberk West. This corresponded well also with concentrations of ammonium nitrogen, dissolved reactive phosphate and total phosphorus in the soil pore water. In contrast, Branna had by far the highest level of total nitrogen, determined by nitrate nitrogen (20 mg l(-1)), and the highest level of total dissolved solids (concentrations of NO3-, SO42-, Ca2+ and Mg2+) of all three sites. No conspicuous differences were found among the three stands in biomass and its allocation. The vegetation composition corresponded more closely to elemental soil composition than to total nitrogen or total dissolved solids in the pore water. It is concluded that Branna provides an example of a site subjected to an initiating but dramatic and fast eutrophication while conditions at the two Rozmberk sites indicate a slower but longer lasting eutrophication. Owing to continuous heavy organic loading, Rozmberk West represents a hypertrophic site characterised by the highest levels of organic matter and associated characteristics (soil C, N, P, K, dissolved P), but also by the most severe lack of oxygen of the three sites. (C) 2001 Elsevier Science B.V. All rights reserved.