The Holocene history of highland pine forests in a submediterranean mountain:: the case of Gredos mountain range (Iberian Central range, Spain)

The significance of Pinus sylvestris and Pinus nigra forests in Gredos mountain range in the Iberian botanical literature has been traditionally a matter of controversy. Considered for many botanists to be anthropogenic forests, a high amount of syntaxonomic approaches, cartographies of potential vegetation and dynamic models have been created based on this guesswork. Nevertheless, this work contributes new data that contradicts this previous hypothesis. For the first time, these data prove the existence of a bioclimatic belt where pine trees dominated during the last 6500 years, clarifying its altitudinal range, surface extension, and its stability. The study is based on the analysis of fossil macrorests and megarests, dated using radiocarbon. The results obtained cohere with the suggestions of other authors that assume the native character of P. nigra and P. sylvestris in this area, based on data of diverse origin (palynological. historical, toponymical, dendrochronological or geobotanical). The paper then continues to discuss the geobotanical interpretation of the results and the regional lines of management, as well as the potential causes that could have induced the marked decline of pine forests in the last millennia. (C) 2007 Elsevier Ltd. All rights reserved.