The vegetation development and drift-sand dynamics in the Kootwijkerveen, the Netherlands: the role of human impact and climate variability

Abstract

After a period of reforestation during the Migration Period, population increase was accompanied by a strong intensification of agriculture. In the European sand-belt, this intensification of agriculture led to large-scale resedimentation of Weichselian coversand deposits, creating drift-sand areas. Several drift-sand deposits are located in The Netherlands, of which the areas in Drenthe (e.g. the Aekingerzand) and Gelderland (e.g. the Kootwijkerzand) are discussed in more detail. Since archaeological evidence of human settlement is present near the Kootwijkerzand, this site was chosen as a research area for this study. The drift-sand dynamics and vegetation development were reconstructed for the period 1-1500 AD, and the influence of climate and human settlement was assessed. In general, in this area, the anthropogenic influence on the vegetation development surpassed that of the climatic influence. However, a short phase of deforestation recorded in the first stages of peat growth could have been related to a decrease in precipitation. In this study only one phase of drift-sand influx was found, whereas in other studies several different phases were found. This could indicate that the influx of drift sand was variable throughout the area. A relatively closed woodland was present in the region until the human influence increased, creating open places with herbaceous vegetation and crop cultivation. The human impact increased further from the 10th century onward, as can be inferred from an increase in cereal pollen percentages and the presence of cornflower. Locally, fluctuations of the groundwater table were observed, both in the bog itself and in the direct surrounding. Only during the final stage of peat growth a slight increase of drift-sand influx was found, simultaneously with the presence of an open environment and an increase in human impact indicators. After this, aeolian influx increased significantly in a short period of time, stopping peat growth. Sand drifting continued in this region until active reforestation from the 17th century onward.