Spatial heterogeneity of water pathways in degenerated riverine peatlands

Riverine peatlands are hydrological buffer zones between terrestrial. and aquatic ecosystems. Under natural conditions they fulfil. important ecological functions such as nutrient retention, flood mitigation and conservation of wetland biocoenoses. In Western Europe, most riverine peatlands have lost these functions due to increased drainage and land use intensity. Before starting restoration measures in degenerated areas an analysis of the local hydrological conditions is required to assess potentials for nutrient retention and re-establishment of characteristic biocoenoses. In this study, we carried out such an analysis in a degenerated riverine peatland of Northern Germany (Upper Eider valley). First, we characterized different water pathways according to their nutrient concentrations. The evaluation revealed three important pathways: (a) water of springs with high nitrate concentrations (medians between 4 and 21 mg l(-1) NO3-N) and both low ammonium and ortho-phosphate concentrations; (b) water of springs with tow nitrate concentrations; and (c) water of peat drains with tow nitrate concentrations but both high ammonium (medians between 0.6 and 1.4mg l(-1) NH4-N) and ortho-phosphate concentrations (medians between 0.07 and 0.17mg l(-1) PO4-P). A hydrochemical screening in two subareas pointed out, that the heavily drained subarea was characterized by a high density of drains and oxic, nitrate-polluted springs near the sandy slopes. In this subarea, potential for nutrient input to the river was higher than in the weakly drained subarea, in which drains were lacking and nitrate entering the peatland by shallow groundwater was denitrified. Spatial heterogeneity of water pathways was high in both subareas. We concluded, that a screening of all pathways is necessary to assess the restoration potentials of degenerated riverine peatlands. In some cases, pathways such as drains or ditches without contact to springs can be characterized in the area without measurements of their nutrient concentrations. In other cases, such measurements are indispensable to distinguish between different springs. However, our results have also shown, that a single measurement is sufficient to characterize also these water pathways. (c) 2006 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.