During the glacial episodes of the Quaternary, European forests were restricted to small favourable spots, namely refugia, acting as biodiversity reservoirs. the Iberian, Italian and Balkan peninsulas have been considered as the main glacial refugia of trees in Europe. In this study, we estimate the composition of the last glacial forest in a coastal cave of the Cilento area (SW Italy) in seven time frames, spanning from the last Pleniglacial to the Late Glacial. Charcoal analyses were performed in seven archaeological layers. Furthermore, a paleoclimate modelling (Maxent) approach was used to complement the taxonomic identification of charcoal fragments to estimate the past potential distribution of tree species in Europe. Our results showed that the mesothermophilous forest survived in this region in the core of the Mediterranean basin during the Last Glacial Period (LGP, since ~36 ka cal BP), indicating that this area played an important role as a reservoir of woodland biodiversity. Here, Quercus pubescens was the most abundant component, followed by a wide variety of deciduous trees and Pinus nigra. Charcoal data also pointed at the crucial role of this coastal area, acting as a reservoir for warm temperate trees of genera Tilia, Carpinus and Sambucus, in LGP, in the Mediterranean region. Our modelling results showed that P. nigra might be the main candidate as a “Pinus sylvestris type” in the study site in the Last Glacial Maximum (LGM). Furthermore, we found that P. nigra might coexist with Q. pubescens in several European territories both currently and in the LGM. All models showed high levels of predictive performances. Our results highlight the advantage of combining different approaches such as charcoal analysis and ecological niche models to explore biogeographic questions about past and current forest distribution, with important implications to inform today’s forest management and conservation.

中文翻译：

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地中海盆地沿海松橡木冰川避难所：基于木炭分析和空间模型的生物地理学方法

在第四纪的冰川时期，欧洲森林被限制在作为生物多样性保护区的避风地（refugia）。伊比利亚，意大利和巴尔干半岛已被视为欧洲树木的主要冰川避难所。在这项研究中，我们估计了从最后一个冰期到晚冰期的七个时间框架内奇伦托地区（意大利西南部）沿海洞穴中最后一个冰川森林的组成。在七个考古层进行了木炭分析。此外，古气候建模（Maxent）方法用于补充木炭碎片的分类学鉴定，以估计欧洲树木过去的潜在分布。我们的结果表明，在上个冰期时期（LGP，自约36 ka cal BP以来），在地中海盆地中心的该区域中，嗜温性森林得以幸存，这表明该地区作为林地生物多样性的储库发挥了重要作用。这里，毛栎是最丰富的成分，其次是各种各样的落叶乔木和黑松。木炭数据还指出了该沿海地区的重要作用，它是地中海地区LGP中Tilia，Carpinus和Sambucus属温带温带树木的蓄水池。我们的建模结果表明，在最后冰期最大值（LGM）的研究地点，黑松可能是“樟子松类型”的主要候选对象 。此外，我们发现黑假单胞菌可能与白毛Q. pubescens共存目前以及在LGM中在几个欧洲领土上都存在。所有模型均显示出较高的预测性能。我们的结果凸显了将不同的方法（如木炭分析和生态位模型）相结合来探索有关过去和当前森林分布的生物地理学问题的优势，这对于当今的森林管理和保护具有重要意义。