Vegetation changes in the Grote Nete valley (Campine region, Belgium) during the Boreal: a response to the 9.3 ka event?

Abstract

Environmental changes have had an enormous impact on prehistoric hunter-gatherers as they affect the biotic landscape and availability of resources such as freshwater, edible plants, game and fish. To assess whether various innovations that took place in hunter-gatherer communities during the Boreal may be attributed to changes in the vegetation, a high-resolution pollen and macrofossil analysis of a well-AMS-dated Early Holocene peat record from the Grote Nete valley in the Belgian Campine was carried out. Shifts in the pollen assemblages indicate a change from a birch-pine woodland in the late Preboreal to pine-dominated forests in the Boreal. After the initial expansion of hazel, followed by oak and elm from the early Boreal onward, a prominent and abrupt reduction of the pollen concentration, by up to 95% over several spectra, is observed during the second half of the Boreal. This sharp decline affects all taxa and coincides with a decrease in pollen percentages of thermophilous trees and an increase of the cold-tolerant pine. This shift in pollen concentration and vegetation composition likely reflects a climatic cooling at 9.3 ka which is evident in the stable oxygen isotopic record of the Greenland ice cores. On the one hand, the vegetation dynamics are discussed in the light of the Boreal vegetation history in general and this temporary cooling more specifically. On the other hand, we discuss how these changes may have affected past hunter-gatherer communities.