The dialectic between deciduous and coniferous forests in central Iberia: A palaeoenvironmental perspective during the late Holocene in the Gredos range.

Abstract

Pollen analyses supported byfifteen AMS14C dates from Fuente de la Leche (1382 m) and Fuente del PinoBlanco (1343 m) peat sequences, in the Gredos range (central Spain), are used to reconstruct the lateHolocene vegetation history in this mountain region. These results are compared with other sequencesfrom the Spanish Central System in order to better understand the past dynamics of the main forestconstituents and to provide a critical view of the dialectic between conifers and deciduous forests. Thevegetation record at Fuente de la Leche starts at 3000 cal yr BP, with the occurrence of rather closedforests composed ofPinus sylvestrisandBetula.Pinus sylvestriswas the dominant pollen taxa for almostthe entire period. However, during the last 850 years,Pinus sylvestrisforests were progressively replacedbyQuercus pyrenaicawoodlands and grasslands, as a result of a high pastoral pressure, until formingmixed woodlands ~400 years ago. The interpretation of Fuente del Pino Blanco record is that dramaticchanges started about 265 years ago. Prior to this date, an open canopy woodland included species (Alnusglutinosa,Quercus pyrenaica) whose distributions no longer exist in the studied area. We suggest that theincrease in agricultural (rye and other cereals) and livestock activities forced a change in the role offire inthe supramediterranean belt of the Gredos range, thus Pyrenean oak canopy was consumed byfires,providing openings forPinus pinasterand broom communities better adapted tofire.