Formation, vegetation succession and acidification of a Mid-Holocene moorland pool in the western Netherlands

We studied a Holocene peat fill of a small depression in Pleistocene coversand, in the western border zone of Het Gooi, to assess the early local and regional vegetation history in relation to sea-level rise, soil development and potential human impact. In the fourth millenium BC, a podzol which had formed in the depression became stagnative, leading to the development of a moorland pool. The local vegetation changed from dry heathland, through an amphibic vegetation type with, among others, Littorella uniflora and Lycopodiella inundata, to a permanently moist Sphagnum- dominated vegetation. The existence of moorland pools and the development of such habitats into Sphagnum- dominated vegetation are known from Late Holocene anthropogenic, more or less open landscapes that were formed on a podzolising sandy soil under ericaceous vegetation. However, the recorded vegetation succession did not show any recognisable local human impact and therefore is attributed to natural succession. In the period concerned, sea level was still about 4 m below the land surface in the depression, implying that water logging occurred independent from a rise in sea level and associated groundwater level. It took until the Late Middle Ages before such rise led to significant water logging and peat growth in this border zone, but the mean groundwater level never reached to above NAP ( Dutch Ordnance Datum).