Vegetation dynamics and human impact in the Sierra de Guadarrama, Central System, Spain

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Abstract
Analyses of pollen, non-pollen microfossils and carbonaceous particles from a valley mire in the Lozoya Valley in the Sierra de Guadarrama, which forms part of the Spanish Central System, are presented. The sedimentary sequence, which covers the last 8500 years, provides one of the oldest records in the central sector of this mountain chain. The core displays evidence of well developed Pinus sylvestris forests coupled with the presence of taxa such as Castanea or Olea in the early Holocene, highlighting the value of near-tree-line montane enclaves in the reconstruction of vegetation dynamics. The results show that the Lozoya Valley was an important refugial area for thermophilous taxa and that taxa like Olea and Castanea were present in pre-Roman times in this part of the Central System. In contrast to other areas of Spain and elsewhere in Europe where Quercus replaces Pinus in the early Holocene, evidence is presented of a natural pine belt in the Iberian continental montane system throughout the Holocene. The first signs of human impact are recorded in the pollen record at about 3740 BP, but major deforestation of the montane forests belts in the Sierra de Guadarrama is not visible until c. 1000 BP. This date is similar to dates for maximum human pressure in other Iberian environments and appears to be synchronous with a flourishing socioculture in Spain