Diversity, Distribution and Postglacial History of Native Pinus sylvestris Forests in the Iberian Peninsula

Abstract

Aim: Pinus sylvestris is the most widely distributed Pinus species in the world, highlighting its ecological, economic and socio-cultural importance. The Iberian Peninsula marks its south-western distribution limit, whose extent has been significantly reduced since the Mid-Holocene. In this study, we investigated the current diversity of native Pinus sylvestris forests in the Iberian Peninsula and their postglacial distribution and history. Location: Iberian Peninsula, south-western Europe. Taxon: Pinus sylvestris L. Methods: We compiled 1299 vegetation plots from native Pinus sylvestris forests and performed a numerical classification, modified TWINSPAN, to identify major forest types. We characterized their floristic composition, diversity and environmental drivers. Ecosystem Distribution Models were fitted using climatic and edaphic variables to estimate their potential distributions during the Last Glacial Maximum (21 ka BP), Mid-Holocene (6 ka BP) and present. Model outputs were validated with palaeobotanical records. Results: We identified four different forest types: acidophilous oromediterranean, acidophilous temperate, basophilous, and thermophilous mixed forests. These forests host unique assemblages of endemic, relict and broadly distributed plant species. Ecosystem Distribution Models revealed that, among the three studied periods, present climatic conditions are the most suitable for the development of Pinus sylvestris forests. Yet, their present-day distribution is considerably more restricted than predicted, a mismatch that agrees with palaeobotanical records. Main Conclusions: Native Pinus sylvestris forests in the Iberian Peninsula display a wide ecological range. Their current distribution is more restricted than expected by suitable climatic conditions, suggesting the key role of anthropogenic historical pressures. Conservation strategies should not only consider future climate scenarios but also integrate historical land-use legacies.