Het palynologisch onderzoek van de Hassebergril (Sellingen, Gr.)
The palynological examination of an early medieval peat deposit in the brook-valley system Hassebergril (Sellingen, province of Groningen). An analysis was made of the pollen content of a peat deposit in a brook valley, the Hassebergril (Sellingen, province of Groningen). The subsoil beneath the peat deposit is composed of eroded sandy loam. On the basis of just one radiocarbon date, the indigenous woodland and peat moss deposits have been attributed mainly to the Merovingian and Carolingian period (AD 500-750 and 750-900, respectively). The local pollen record of this period shows a successive domination of different vegetation types. During the formation of carr peat (Zone II), alder-and-willow carr and scrub of gale were locally common. In the next phases (Zone III and IV) sedges (including cotton-grass), grasses, peat mosses and heather successively dominate this part of the valley. Very wet conditions prevailed during Zone III, when pools formed locally with occasional aquatics such as pondweed and white water lily. The significant increase of heather in Zone IV is thought to be largely due to the expansion of local vegetation, resulting from progressively drier conditions in the brook valley. During the period discussed, fairly open woodland, in places alternating with heather and grassy vegetation, predominated outside the brook valley. The scattered occurrence of ribwort plantain in almost all spectra indicates small-scale cattle herding, which could have prevented woodland regeneration in parts of the area. In the uppermost part of the diagram (Zones III and IV) small shifts in the regional arboreal vegetation are evident. Especially the pollen values of beech and hornbeam in this part are substantial and uncommonly high compared to the usually minor values in the pollen diagrams of the Drenthe Plateau. The changes in the arboreal vegetation may be a natural development, but might also signal a gradual shift in the agricultural system towards crop cultivation, as is suggested by the appearance of scattered pollen grains of rye in the uppermost section of the diagram.