Transformations of Wetlands in N-E Poland Postglacial Landscape and Its Relation to Lake Water Quality

Abstract

Using an input-output ecosystem model, it was demonstrated that wetlands of the various stages of anthropogenic transformations typical for the postglacial landscape of N-E Poland vary in nitrogen (N) and phosphorus (P) forms retention. It concerned particularly nitrates (NO₃-N) and phosphates (PO₄-P), the most responsible for eutrophication effect. The calculation of retention effectiveness for studied wetland ecosystems showed that undrained minerotrophic peatland and transition bog retained about 70–85% of total N, including 95% of nitrates, but at the same time, they lost more than 50% of incoming phosphates. Wetlands with a shallow lake or transition bog crossed by a watercourse were considered as typical through-flowing systems with at most a moderate tendency to retained phosphates. Drained peatlands were considered dangerous in exporting N and P forms into recipient lakes and rivers. A directly drained minerotrophic fen lost even 70% of nitrates in the first year after melioration. Formerly drained peatlands can also lose nitrates, but first of all, they lost even 80–100% of total phosphorus input. All drained peatlands examined did not retain or lose total nitrogen and phosphates.