Potkleibossen in Noord- en Oost-Drenthe: Ondergrond, cultuurgeschiedenis en vegetatie

Two specific regions in the north and east of the province of Drenthe (northern Netherlands) contain shallow heavy clay soils that date from the Elsterien Ice Age (475,000—410,000 years BP). As these soils are unsuittable for human settlement or arable farming these regions include a relatively high number
of ancient woodlands. The paper describes the geological, cultural-historical and ecological characteristics of three of these woodlands. Glacial clay soils dating from this second—tolast ice age occur exclusively in places where all younger sediments have been eroded. This is only the case at the edge of the Drents
Plateau. The blackish grey clay layers are extremely stagnant, making them suitable for nothing but grassland. But in the Middle Ages the clay was found to be very well suited for the production of bricks and tiles.This is why the largest monastery in the Netherlands — the Cistercian Abbey of Aduard — founded several brick and tile factories in these glacial clay areas in the 13th and 14th centuries. In the 16th and 17th centuries local noblemen and industrial entrepreneurs took over this brick industry, which remained active until the mid-20th century. The best preserved brick-production landscape is in the ancient woodland of De Kleibosch (Foxwolde), where numerous clay pits, field oven relics and heaps of misfired bricks are the silent witnesses of this historical brick industry. Most ancient woodlands on glacial clay soils
have been used as commons by local farmers since medieval times. Written sources like village by-laws tell us that these woodlands produced vast amounts of oak timber, coppice wood and faggots, and were also extensively used for herding cattle and pigs. Because of their rich clay soil and long history of human
exploitation, the last five remnants of this particular type of ancient woodlands contain a unique flora including more than 25 native tree and shrub species and many rare ancient woodland plants. Even though the original woodland was reclaimed in the 19th and 20th centuries, the hedges and woodbanks appear
to contain many relics of this ancient woodland vegetation. They therefore deserve speccial attention from researchers, nature managers and politicians to guarantee a sustainable future for these very rare historical-ecological landscapes.