History of vegetation during the Holocene in the Courel and Queixa Sierras, Galicia, northwest Iberian Peninsula

Palynological studies undertaken in the mountainous regions of the northwes t of the Iberian Peninsula are few in number and have been concerned largel y with the second half of the Holocene. New pollen data from two Galician s ierras, the Courel and Queixa Sierras, provide a 10000-yr record of vegetat ion and climate change. In the Courel Sierra before 9750 yr BP, Laguna Luce nza (1420 m a.s.l.) reflects a period of open landscape covered by Poaceae and heliophilous plants, which may be correlated with the Younger Dryas. Th e onset of the Holocene is characterised by the expansion of oak woodland, prior to 9300 yr BP, following a short phase of birch along with the gradua l decline of pine. The oak values reach a peak at 8350 +/- 80 yr BP. Toward s 8800 yr BP Corylus begins to expand, followed by Alnus (7500 yr BP) and U lmus. During this period, the Fraga pollen assemblage (Queixa Sierra, 1360 m a.s.l.) indicates Betula woodland surrounding the site, masking the regio nal predominance of oak. After 5000 yr BP there is a gradual decrease in ar boreal pollen values in both Sierras. Castanea appears in Laguna Lucenza (C ourel Sierra) at 4075 +/- 75 yr BP. There is widespread deforestation durin g the last 4000 yr. During this period the presence of large quantities of microcharcoal particles points to the occurrence of fire. The reduction in forest is associated with the arrival of cultivation at 4000 yr BP at low a ltitudes in the Queixa Sierra. At higher altitudes the first agricultural a ctivity is dated at later than 2000 yr BP. This coincides with the first re cord of cereal cultivation at high altitude in the Courel Sierra. Copyright (C) 2000 John Wiley & Sons, Ltd.