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The study of a pollen sequence obtained from a peat deposit in Hoyos de Iregua (Iberian Range, north-central Spain) has been carried out, revealing new information about the vegetation dynamics and climate changes since Late-glacial times. Pollen zones have been defined corresponding to successive phases in vegetation history during the end of the Late Wurm (Oldest Dryas, Late-glacial interstadial, Younger Dryas) and the Holocene. During the Oldest Dryas event, there was a sparse vegetation cover dominated by herbaceous taxa, with Pinus as the unique arboreal taxon with some importance. The vegetation landscape during the Late-glacial interstadial (13,000–11,000 yr BP) corresponded to coniferous forest and mixed forests, including the presence of evergreen Quercus . Between the Late-glacial and the Holocene, a brief cooler and drier phase occurred, the Younger Dryas event (11,000–10,000 yr BP). During this period an important reduction of the tree masses characterized the evolution of the landscape. The Holocene began with a period of increasing temperature that resulted in an expansion of the arboreal elements, which reached their highest representation during the Holocene Climatic Optimum. From 5060±90 BP a change to more arid conditions occurred, favouring the development of the mediterranean vegetation. Within the Late Holocene, clear evidence of the human impact on the environment are detected, being more accentuated towards the uppermost levels. |
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