Eemian reforestation patterns in central Italy, a palynological comparison between a lowland basin (Valle di Castiglione) and an intramontane basin (Piana del Fucino).

The onset of the Eemian interglacial (MIS 5e) represents a critical interval for investigating vegetation responses to rapid climate warming and changes in hydroclimatic seasonality in the Mediterranean region. While forest expansion during early interglacial phases is rather well-documented, the degree to which reforestation pathways differed within the same geographic region across contrasting physiographic settings, remains insufficiently explored. Here we present a palynological comparison of early Eemian vegetation development at two central Italian sites characterised by different topographic and climatic contexts: Valle di Castiglione, a lowland crater lake of Alban Hills, located in the alluvial plain close to Rome, and the Fucino Basin, a wide intramontane dried out lake situated in the central Apennines. The explicit aim of this comparison is to assess whether early Eemian reforestation followed synchronous or differentiated trajectories in lowland versus intramontane settings, and to evaluate the role of altitude, basin morphology and continentality on modulating forest establishment and stability.

Preliminary pollen data from Valle di Castiglione carried out in the frame of AMUSED project (https://progetti.ingv.it/it/amused), indicate a rapid expansion of arboreal taxa at the MIS 6–MIS 5 transition, associated with increasing temperature and precipitation and the rapid establishment of predominantly mesophilous and Mediterranean vegetation during MIS 5e. These lowland dynamics are compared with evidence from the Fucino Basin, one of the most complete and sensitive terrestrial archives in the Mediterranean and a key reference for vegetation–climate relationships in central Italy. The comparison is explicitly designed to explore whether early Eemian reforestation followed synchronous or differentiated pathways in lowland coastal versus intramontane environments. This lowland record is compared with the high-resolution, radiometrically constrained pollen sequence from the Fucino Basin recently presented by Roberts et al. (2025), which provides a detailed reconstruction of vegetation dynamics between ~139 and 107 ka based on a robust tephrochronological framework. The Fucino record shows that early Eemian forest expansion was not monotonic but involved a rapid increase in many temperate deciduous taxa interspersed with centennial-scale fluctuations and transient reductions in forest cover.

This contribution is conceived as a pilot and contextual study in support of the ICDP proposal for the drilling of the Fucino paleolake (MEME project – the longest continuous terrestrial archive in the Mediterranean recording the last five million years of Earth system history), which aims to recover a continuous, high-resolution and chronologically robust record of environmental change across the entire basin infill. By placing early Eemian vegetation dynamics from Valle di Castiglione into a regional comparative framework with Fucino, this study provides a first step towards disentangling the role of altitude, basin setting and climatic gradients in shaping interglacial reforestation patterns in central Italy.

 

Roberts, C. A., Zanchetta, G., Giaccio, B., Nomade, S., Mannella, G., Sadori, L., ... & Tzedakis, P. C. (2025). A radiometrically-constrained reference record of Last Interglacial climate and vegetation changes from the Fucino Basin, Central Italy. Quaternary Science Reviews, 363, 109377.