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 compo sition and horizontal stand structure were investigated for three reed stan ds in the Trebon Basin (Czech Republic): Branna sand pit and two littoral s tands of Rozmberk fishpond (Rozmberk East and Rozmberk West). Phragmites st ands were expanding, stable and retreating at the three sites, respectively . The elemental soil composition (especially of C, N, P, and K) indicated t he lowest trophic conditions at Branna, intermediate at Rozmberk East and t he highest at Rozmberk West. This corresponded well also with concentration s of ammonium nitrogen, dissolved reactive phosphate and total phosphorus i n 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 highe st 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 corr esponded more closely to elemental soil composition than to total nitrogen or total dissolved solids in the pore water. It is concluded that Branna pr ovides an example of a site subjected to an initiating but dramatic and fas t eutrophication while conditions at the two Rozmberk sites indicate a slow er but longer lasting eutrophication. Owing to continuous heavy organic loa ding, Rozmberk West represents a hypertrophic site characterised by the hig hest 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 s ites. (C) 2001 Elsevier Science B.V. All rights reserved.