*4.2. Vegetation Cover of the Pleniglacial*

The vegetation, inferred at three temporally distinct episodes, was located close to the coastal caves, in a wide coastal plain including currently submerged sectors. Indeed, between 30 and 19 ka cal BP the coastline would have been about 8 km away from the present one, due to sea level lowering [75].

In both the oldest layers, namely at ~36 ka cal BP and at ~29 ka cal BP vegetation cover at the site can be envisaged as woodland with coexisting *P. nigra* and deciduous mesoxerophilous trees with *Q. pubescens* and *Acer*, which summed together, account for the 50% of the charcoal assemblage. Interestingly, the youngest layer falls in the cold arid period detected in the Salerno Gulf, ~80 km to the north, spanning between 34 and 27 ka cal BP [76]. In this phase, despite the occurrence of the lowest values of annual temperatures [TANN (7◦ C)], July temperatures [TJUL (20◦ C)] and annual precipitation [PANN (400 mm year<sup>−</sup>1)], it seems that in Camerota Bay the amount of precipitation may still support the development of forest vegetation.

At ~19 ka cal BP, vegetation is still dominated by *Q. pubescens* and *Fraxinus* (up to ~70%), but the number of pine charcoals appears significantly reduced. The age of this layer falls in the LGM, as defined by EPILOG [77] during which cold arid conditions are inferred for the whole Mediterranean area [78]. However, at the regional scale, this period coincides with the end of a relatively warm-humid phase (25.5 to 18.5 ka cal BP [76]) also recorded at Monticchio (~100 km NE) between 25 and 20 ka BP [79] which might explain the high amount of *Q. pubescens* and *Fraxinus*. This may well have disadvantaged the light-demanding *P. nigra* [80] which probably was restricted to the rocky slopes with thin soils. Overall, during the Pleniglacial, our data suggest a stable forest cover with temporal phases of dominance variation between *Pinus* and deciduous trees.

The presence of a continuous forest cover in the Camerota Bay is also confirmed by the presence of woodland mammals such as Gliridae, Muridae and *Clethrionomys* [81,82], while species related to open and steep slope environments are very rare [83]. The broad diversity of micromammal assemblages throughout the Pleniglacial indicates the contemporaneous presence of probably both forested and open environments that periodically expanded and retreated, offering habitats for many taxa [81].

In a wider spatiotemporal perspective, our data are consistent with the pollen record from the Gulf of Salerno [25], where arboreal pollen values are almost always over 30% and deciduous oaks were stable at around 10% (*Pinus* excluded) during the entire Last Glacial Period (LGP). Our data, combined with the evidence of the almost treeless grass-dominated landscape inland and the much higher elevation sites of the Italian peninsula [79,84,85], suggest that most of the arboreal pollen content of these pollen spectra should be ascribed to the coastal sector.

The only Italian pollen record showing a vegetation cover comparable to that shown by our data concerns the north Tyrrhenian coast where until ~28 ka cal BP deciduous *Quercu*s and *Pinus* with *Abies alba* combined to form a dense forest [86].

Roughly at the same latitude as Camerota Bay, the southern Adriatic coast of Italy, at a direct distance of ~200 km, at ~28.5 ka cal BP (24,410 ± 320 BP), was characterised by evergreen vegetation with *P. halepensis*, *Juniperus* and *Pistacia* [87], testifying warmer and drier conditions in this eastern coastal sector.

Such evidence highlights the remarkable vegetation cover heterogeneity in the Italian peninsula both in terms of latitude and longitude during the late Pleistocene, probably due also to a west-east precipitation gradient due to the longitudinal split by the Apennines which intercept and block westerly humid air masses. Our data also highlight the role of local topography on climate: indeed, here, the proximity of the Bulgheria massif probably played a preeminent role in trapping the clouds of the western weather systems spreading from the Tyrrhenian sea.

Interestingly, a good match with our data has also been found along the west Atlantic coast of Portugal, where wood remains of *Pinus nigra*/*sylvestris*, deciduous *Quercus* and *Fraxinus* dated between 34 to 20 ka BP suggest a very similar forest cover [88]; also, in this case, it seems that oceanic humid air masses played a major role.

In our reconstruction of the forest structure, the spatial position of the pioneer and shade-intolerant black pine with low-density canopy overtops a matrix of mesothermophilous winter deciduous broadleaved species. This structure is today detectable in *P. nigra* and *P. leucodermis* relict forests of southern Italy. Indeed, Rauh's canopy architecture model of these pines exhibits in the mature-old ontogenetic stage a tabular canopy with the green crown restricted to the upper third of the stem and large branches similar to the stem [89–91]. This feature favours direct light transmission and thus permits the establishment of relative shade-tolerating trees, grasses and shrubs. We should also speculate on the engineering capability of the pine canopies, which positively modifies the microclimate by affecting near-ground temperatures, soil moisture and wind speed. In such circumstances, these trees, by acting as nurse plants, should facilitate both establishment and survival of the broadleaved tree species.

In Europe, today, mixed *P. nigra* deciduous forests can be seen in the Eastern Alps where it occurs between 200 to 1200 m a.s.l. together with *O. carpinifolia* and *F. ornus*; in southern Bulgaria *P. nigra* grows at low altitudes mixed with *Q. frainetto* and *Q. pubescens;* further, in southern France mixed forests with *Q. pubescens* and *P. nigra* can also be found [92].

Forest vegetation probably that is very similar to the one suggested by our charcoal assemblage is the Beynam forest, located in the Kuyrukçu Mountains, not far from Ankara, in central Turkey [93]. According to Emberger's climate classification, this region is characterised by semi-arid and very cold Mediterranean climate [94]. Thus, the summer temperatures and the coldness of winter are the main factors characterising the climate. This forest is entirely surrounded by steppe and it is dominated by *P. nigra* subsp. *pallasiana, Q. pubescens* and *Juniperus oxycedrus*. Interestingly, in this region holly oak is not a tree but a shrub, and characterises the lowest layer of the forest cover. This present landscape seems to be the most similar vegetation to the Pleniglacial cover in Camerota Bay.

#### *4.3. Vegetation Cover of the Late Glacial*

During the last glacial-interglacial transition (Late Glacial sensu Orombelli et al. [95]), *Q. pubescens* is still the dominant species, accompanied by other deciduous taxa; *P. nigra* is also still present. It should be pointed out that around ~16 ka cal BP new temperate warm taxa such as *Tilia*, *Carpinus* and *Sambucus* appear. This evidence can be interpreted as a clear consequence of the temperature rise and increased soil moisture supply following the beginning of deglaciation. The expansion of *Tilia* recorded in several Late Glacial pollen sequences of southern [96] and central Italy [86,97–101] might reflect an early expansion of that tree from nearby refugia. This hypothesis agrees with the previous ones of shelter

areas for *Tilia* in the lower *thalwegs* of the Mediterranean coastal rivers [102]. The presence of *Populus* agrees with the riparian forest evidence inferred by paleo-shell analysis carried out in the cave [103].

In Layers 8G, 8F, 8E (13.9–13.4 ka cal BP) *P. nigra* declines when *Fraxinus* increases. At this time, in the Gulf of Salerno, a rapid climatic change, culminating at 13.8 ka cal BP, marks the Bølling-Allerød chronozone characterised by the increase in atmospheric temperatures, especially the summer values [TJUL (24 ◦C)], and precipitation [PANN 900 mm)] [76]. Additionally, stable isotopes of land snail shells from the SC layers dated to 14–13.4 ka cal BP suggest moisture conditions quite similar to those of the present day must have occurred. These climatic conditions could have reduced the competitive advantage of *P. nigra* over the broadleaf species, especially with respect to pioneer species such as *F. ornus*. In this respect, it is interesting to note that, in medium and high belt wooded landscapes of Iberian Peninsula, cryophilous pines, that were the main species during the Late Glacial, declined in favour of broadleaved species following Holocene climate amelioration [104].

To sum up, our data suggest that the Cilento coast acted as a refugium for temperate deciduous tree species and *P. nigra*, confirming the coastal environment as a potential reservoir of biodiversity [105,106] and contrasting with the mid-altitude theory based on the assumption that precipitation in this region would have been higher than on the plains [1,2,96,107–109].

Our results remark the usefulness of combining different approaches to explore biogeographic questions about past and current forest distribution—a fundamental step to informing forest management and conservation.

#### **5. Conclusions**

Our results give a very clear picture of bioclimatic conditions in the surroundings of the Camerota caves during the LGP and as late as the Lateglacial. They indicate that the climatic conditions were always able to sustain forest cover. The data show the presence of mesothermophilous forest during the LGP (from ~36 ka cal BP), proving that this area played an important role as a reservoir of woodland biodiversity in which *Q. pubescens* was the most abundant component, followed by a wide variety of deciduous trees and mountain pines, most likely *P. nigra.* ENM projections provided a useful complement to our paleoecological studies, refining charcoal evidence and offering a less subjective picture of past geographic distributions of *Pinus* species in the LGM. Ours is the first study that, by using paleoclimate model and charcoal analysis, suggests the potential presence of a glacial refugium of *P. nigra* on the Tyrrhenian coastal sector of southern Italy, confirming our initial hypothesis. Finally, this work provides punctual evidence of the crucial role of coastal areas as reservoirs for temperate tree taxa in the Mediterranean basin.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1999-4907/11/6/673/s1, Figure S1: Serratura Cave entrance; Figure S2: Presence records of *P. mugo*/*uncinata* after spatial autocorrelation analysis; Figure S3: Presence records of *P. nigra* after spatial autocorrelation analysis; Figure S4: Presence records of *P. sylvestris* after spatial autocorrelation analysis; Figure S5: Presence records of *Q. pubescens* after spatial autocorrelation analysis; Figure S6: Microscopic anatomical features of main identified taxa; Figure S7: Multivariate Environmental Similarity Surfaces (MESS) maps for *P. mugo*/*uncinata* obtained with CCSM4 models for LGM scenarios; Figure S8: Multivariate Environmental Similarity Surfaces (MESS) maps for *P. nigra* obtained with CCSM4 models for LGM scenarios; Figure S9: Multivariate Environmental Similarity Surfaces (MESS) maps for *P. sylvestris* obtained with CCSM4 models for LGM scenarios; Figure S10: Multivariate Environmental Similarity Surfaces (MESS) maps for *Q. pubescens* obtained with CCSM4 models for LGM scenarios.

**Author Contributions:** Conceptualisation, G.D.P., E.A., A.S., L.B. and A.M.; methodology, G.D.P., E.A. and L.B.; software, L.B.; charcoal analysis, G.D.P. and E.A.; formal analysis, E.A., L.B.; resources, G.D.P. and A.M.; data curation, E.A.; writing—original draft preparation E.A., G.D.P. and L.B.; writing—review and editing, D.R., A.S. and G.B.; supervision, E.A.; visualisation, E.A. and L.B.; funding acquisition, A.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding. The APC was funded by PSR CAMPANIA 2014–2020 misura 16.5.1—Azioni congiunte per la mitigazione dei cambiamenti climatici e l adattamento ad essi e per pratiche ambientali in corso Progetto: Cilento: suolo paesaggio e biodiversità (CiSPaB) CUP B12D18000090007, granted to A.S.

**Acknowledgments:** We are grateful to Federica Furlanetto and Mario Marziano for the technical support given in the early phases of the work.

**Conflicts of Interest:** The authors declare no conflicts of interest.
