ENVIRONMENTAL-CHANGE DURING THE MEDIEVAL RECLAMATION OF THE RAISED-BOG AREA WATERLAND (THE NETHERLANDS) - A PALAEOPHYTOSOCIOLOGICAL APPROACH

A report is given of a palaeoecological study based on the analysis of pollen, non-pollen palynomorphs and macrofossils of an excavated medi eval house site and its underlying peat deposit at Poppendam, Waterlan d (The Netherlands). The house site represents one of the first human occupations in this former raised-bog area. The analysis includes a ra ised-bog sequence with cultural layers on top of it. A detailed recons truction of the changing vegetation from natural raised-bog to cultura l landscape is given. The main phases of the deposit comprise: a natur al, undisturbed bog (from mid-Subboreal to the 8th century AD); a dist urbed raised-bog with eutraphentic taxa prior to the first occupation (between the gth century and the first half of the 10th century AD); a n anthropogenic accumulation layer of mixed former bog material, eutra phentic taxa and cultural indicators (from the first half of the 10th century AD onwards). Seeds and pollen of cultivated plants and vegetat ion of the Lolio-Potentillion anserinae alliance indicates a mixed agr icultural economy in which domesticated animals played an important ro le. This is confirmed by the simultaneous occurrence of large numbers of ascospores of coprophilous Sordariaceae. Inundations of Lake Almere , as evident from the occurrence of brackish/salt elements, suggest th at the lake had already become brackish/salt around the 8-9th century. Two methods for the reconstruction of palaeophytosociological communi ties containing halophytic plant species are presented. The Lolio-Pote ntillion anserinae alliance as an indication for inundations, lowering of the original bog surface and the occurrence of grazed, brackish gr asslands is discussed.