The paper aims to define the natural distribution of Olea europaea L. var. sylvestris (Miller) Lehr. in the North Mediterranean basin during the Pleniglacial and the Early-Middle Holocene by means of the identification of its wood-charcoal and/or wood at prehistoric sites.For this purpose we have reviewed the previously available information and we have combined it with new wood-charcoal analyses data. We have taken under consideration the presence and frequency of Olea europaea L. in the available wood-charcoal sequences, the characteristics of the accompanying flora, the associated chrono-cultural contexts, the broader biogeographical context and the AMS dates provided by Olea wood-charcoal or endocarps.According to the available evidence, during the Middle and Late Pleniglacial (c. 59-11,5 ka cal. BP), Olea would have persisted in thermophilous refugia located in the southern areas of the North Mediterranean basin, the southern Levant and the north of Africa. The Last Glacial Maximum (c. 22-18 ka cal. BP) probably reduced the distribution area of Olea. During the Preboreal and the Boreal (c. 11 500-8800 cal. BP) the species started to expand in the thermomediterranean bioclimatic level. In the western Mediterranean, during the Atlantic period (c. 8800-5600 cal. BP), the species became very abundant or dominant in the thermophilous plant formations and expanded to favorable enclaves outside the limits of the thermomediterranean level.
Macroscopic charcoal, pollen and non-pollen palynomorphs were isolated from a colluvial soil located on a small hill in Campo Lameiro (NW Spain) in order to elucidate the vegetation history of the area and its relation to fire and human activities. The presence of macroscopic charcoal throughout the 2.10 m thick soil (42 samples) is evidence of frequent fires during the last c. 6300 years. The charcoal record was dominated by Quercus (probably Q. robur), Ericaceae (probably Arbutus unedo and Erica arborea) and Fabaceae (mainly Genista type). Abrupt changes in the charcoal assemblage are less explicit in the pollen sequence, probably as a result of pollen inflow from the downhill surroundings of the study site. Combined results indicated that the original oak woodland was gradually replaced by pyrophytic shrubs (Ericaceae and Fabaceae) as a result of fire recurrence. Non-pollen palynomorphs strongly suggested that vegetation was deliberately ignited by past human societies to facilitate grazing. No evidence of local agricultural practices was found. Episodes of accelerated shrubland expansion occurred c. 6000—5500 cal. BP, c. 4000—3500 cal. BP and c. 1700 cal. BP, the latter of which caused the definitive settlement of shrublands dominated by Ericaceae and Fabaceae which are nowadays widespread in NW Iberia.
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