Thesis title: The study of a past interglacial vegetation change as a tool to understand the human role in hydrological changes
Examining sedimentary records from previous interglacial periods provides valuable insights into past climate variability and ecosystem responses to warmer conditions. This research addresses significant gaps in our understanding of the global water cycle and ecological adaptations to the current global warming.
This PhD thesis investigates the sediments from Fucino Basin in the Central Apennines, which is an ideal location to study vegetation dynamics within a mountainous and Mediterranean climate during the interglacial period corresponding to Marine Isotope Stage (MIS) 11 (ca. 424-367 ka). The first stage of MIS 11 interglacial complex (MIS 11c; ca. 426–396 ka) is particularly interesting due to the fact that it represents one of the longest and warmest interglacial phases within the last 800 ka, with approximate mean global temperatures 0.5–0.7°C higher and sea level around 6–13 meters above pre-industrial Holocene ones, respectively. In absence of anthropogenic influences, MIS 11c, being an orbital analogue of the Holocene, facilitates the examination of ecosystem responses to naturally warmer climates. High-resolution palynological analyses conducted on Fucino Basin sediments reveal millennial-scale climatic oscillations spanning from 430 ka to 388 ka, including the latter phase of MIS 12 glacial period, the Glacial Termination V (T-V), and most of MIS 11. The Fucino F4-F5 composite record provides one of the few independent radiometrically constrained chronologies for MIS 11, allowing direct comparisons to other regional and global climatic and palynological datasets.
The T-V was one of the most pronounced climatic transitions of the Pleistocene, forming part of the major climatic reorganisation known as the Mid-Brunhes Event (MBE). This event, recorded at 424.5 ± 4.0 ka in Fucino, reflects a substantial shift from a cold, arid phase, with a dominance of herbaceous and xerophytic taxa including Poaceae, Artemisia, Amaranthaceae, Ephedra, and Hippophäe and siliciclastic-dominated sedimentation, to a warm, humid phase marked by increased Abies and a deciduous arboreal assemblage including Quercus, Carpinus, Corylus, and Ulmus, and dominated by a calcareous sedimentation, more organic than in the glacial. The warm and humid conditions recorded throughout MIS 11c in Fucino are consistent with climate reconstructions from other central Mediterranean sites, such as Lake Ohrid and Ioannina, where similarly humid conditions are recorded. Notably, Abies dominated the surrounding vegetation in the Fucino Basin, evidencing high regional humidity.
The Fucino Basin pollen record reveals the sensitivity of mesothermic and altitudinal taxa to insolation fluctuations. A significant arid event occurred between 415 ka and 413 ka, dividing the two precessional cycles that formed the MIS 11c interglacial. This event, described in the palynological record for the first time, may correspond to a global climate signal, as it aligns with lower sea surface temperatures and drier conditions in other records.
This study also developed pollen-based quantitative paleoclimatic reconstructions using weighted averaging partial least squares (WA-PLS) regression. These reconstructions allow for direct comparisons with current climate parameters, elucidating the impact of natural climatic oscillations on vegetation dynamics during MIS 11c. The results show that vegetation dynamics in the Fucino Basin was highly influenced by insolation-driven climate variability, which contributes to a better understanding of past climate dynamics and vegetation responses.
This PhD thesis provides both qualitative and quantitative data that are important for contextualising current anthropogenic impacts on ecosystems by contrasting them with natural climatic and ecological trends observed in the orbital interglacial analogue MIS 11c. These findings highlight the relevance of paleoclimatic studies in improving our understanding of natural climate variability and its implications for future climate responses.