Resilience,vulnerability and conservation strategies in high-mountain pine forests in the Gredos Range,central Spain

Background: High-mountain pine forests and broom communities in central Spain today have led to contrasting interpretations of their natural or human-induced origin.

Aims: We evaluated the vulnerability and resilience of high-mountain Pinus sylvestris/P. nigra forests and derived Cytisus broom scrub communities to climate and anthropogenic disturbances.

Methods: We assessed historical transitions from forest to scrub and their relation to climate and human influences, using a multi-proxy paleoenvironmental study (pollen, non-pollen palynomorphs, charcoal, magnetic susceptibility) in three mires in the Gredos Range, western Iberian Central System.

Results: High percentages of Pinus sylvestris/nigra pollen and the identification of their macro remains demonstrated that high-mountain pine forests have been present in the oromediterranean bioclimatic belt of the Gredos Range since the mid-Holocene. After that, a major human-induced decline, enhanced by climate conditions, has led to their gradual replacement by broom communities.

Conclusions: Broom communities are derived from ancient pine forests that were intensively transformed by human activities after 700 cal year BP, and largely disappeared by ca. 500 cal yr BP. Today’s landscape, dominated by broom scrub and grasslands with scattered stands of pines, shows high resilience and provides suitable refugia for a rich mountain biodiversity which deserves a further protection.