A palaeoecological and chemical study of a peat profile from the assendelver polder (The Netherlands)

Abstract

The unique situation of the Assendelvr area in the western Netherlands in which both marine influences and oligotrophic bog development are detectable enables a detailed reconstruction fof the local and extra-local vegetation development based on the analysis of pollen and other micro- and macrofossils. The vegetation succession series started as a Phragmites swamp (c. 2177–2282 ccal yr. B.P. where ccal is calculated calibrated) and developed through a Molinia fen phase (c. 2060–2177 ccal yr B.P.) into a bog dominated by Ericaceae, Sphagnum and Eriophorum (c. 1008–2060 ccal yr B.P.). In contradiction to former suggestions, Myrica forms local patches pf C. 15–20 m 2 within natural mires with Molinia and heathers. The regional vegetation development of the coastal dune area seem to be recorded better in the peat section than in the dunes itself. There is evidence for the presence of alder brook forest in the area of the Oer-IJ estuary, but not to a large extent. Several time scales have been calculated, using calibrated radiocarbon ages and depths, and also pollen densities. Based on calibrated radiocarbon ages and bulk densities the approximate rates of peat accumulation (in g m −2 yr −1, and in cm yr −1) were calculated. C/ N ratios were determined for each sample. The C/ N ratios reflect the differences in the local floristic composition of the peat and are correlated with the proportion of the coarse plant material in the peat. For the first time information concerning inorganic constituents of peat profiles in the Netherlands is given. They are compared with results from other countries. The inorganic constituents exhibit several patterns: the ash, silica, iron and potassium contents appeared to be correlated with the type of peat and the amount of clastic material in the peat. The sodium content is correlated with the decreasing marine influence. Manganese and iron are thought to reflect the increasing human influence in the dune area (i.e. increasing deforestation) in the upper half of the section. The amount of phosphorus seems to be correlated with Eriophorum roots. The content of fungal hyphae of the samples is strongly correlated with the quantities of rootlets of Ericaceae.