Past, present and future distributions of Oriental beech (Fagus orientalis) under climate change projections

exception is the profile from the Sea of Marmara (core MD01-2430) that records beech with moderate abundance during the LGM. No suitable sediments recording the plant cover during the LGM are known from the southern Caspian area. This might be due to the marked drop in sea level (-50 m) of the Caspian Sea during this period [82]. In contrast, MH distribution of F. orientalis was continuous and abundant throughout its present range from eastern Bulgaria, the Sea of Marmara, northern Turkey, Crimea, the western Caucasus, and the southern Cas- pian Sea region. Percentages commonly are way above the proposed threshold values indicat- ing local presence of Fagus reported in Lisitsyna et al. [51]. Moreover, we did not find convincing evidence for the presence of beech during MH outside its present distribution range. Two pollen profiles from Cappadocia and Lake Van have sporadic occurrences of Fagus pollen but these are very few pollen grains and most likely indicate LDD. This is also suggested by the overall composition of these pollen floras (open oak woodland in the Acıgo¨l area of Cappadocia [69], forest steppe in the Lake Van area [70]). Future projections The combined results from both global climate models with different scenarios show that in the future, the main geographical shift of F. orientalis will be towards the northeast of its present distribution. According to the RF model, a severe range contraction of the species is expected in relation to the present distribution provided by the projected model and the

Fig 2. Past range projections with random forest algorithm; here only MIROC-ESM is shown (for CCSM4 see S8 Fig). Occurrence probability of the species is increasing from grey to red (absence to presence) for a) LGM and b) MH. Dots are indicating pollen records (Table 4). https://doi.org/10.1371/journal.pone.0242280.g002 PLOS ONE Species distribution modeling of Oriental beech (Fagus orientalis) PLOS ONE | https://doi.org/10.1371/journal.pone.0242280 November 17, 2020 7 / 19