Journal of Archaeology in the Low Countries 3-1 (November 2011)Felix Weijdema; Otto Brinkkemper; Hans Peeters; Bas van Geel: Early Neolithic human impact on the vegetation in a wetland environment in the Noordoostpolder, central Netherlands
5 Discussion

Reconstruction of vegetation development

The presence of Alnus, Ulmus and Tilia pollen in the sandy soil points to an Atlantic (approximately late Mesolithic) age (Van Geel et al. 1981) of the base of the studied profile. Before peat growth started (Zone Ia), the presence of spores and macrosporangia of Salvinia indicate local aquatic conditions. The presence of Salvinia is followed by Riccia (Zone Ib), probably indicating alternating wet and dry conditions. On the higher parts of the dune a Tilia forest was present with some open areas where Artemisia, Asteraceae and Brassicaceae were growing. As a result of a rise in the groundwater level, the Tilia forest disappeared and a wetland forest with Alnus and other marsh- and wetland species could develop.

The variety of herbaceous taxa increased when the first cereal cultivation started (Zone Ib). The landscape became more open and richer in nutrients, favouring plants such as Solanum dulcamara, Valeriana and Succisa (Zone Ib and Zone II).

Later, the Alnus forest declined and a Salix carr could develop in most wet areas. Furthermore, the crops and the species associated with meadows declined when conditions became wetter (Zone III). Lythrum, Alisma, Mentha and Typha were found in the nutrient-rich marshes (Zone IVa). Open water was present in the lower parts down slope, but whether there was permanent open water or seasonal inundations is not clear.

On the dry parts of the dune Quercus trees and meadow plants remained present. When Salix declined, many other trees became less important (Zone IVb). Poaceae, filices and Cyperaceae increased and the landscape became an open wetland. Corylus and Pteridium probably inhabited the slopes of the dunes and forest edges.

During the upper part of the studied profile Myrica shrubs developed in the area (Zone V). Myrica possibly was growing on the drained, decaying peat surface and there may have also been some cover of wet forest of Alnus and Salix Chenopodiaceae were linked to increased brackish or marine influence in the landscape.