Contrasting patterns of climatic changes during the Holocene in the Central Mediterranean (Italy) reconstructed from pollen data

Abstract

Lake-level records from Italy suggest a north–south climatic partition in the Central Mediterranean during the Holocene with respect to precipitation, but the scarcity of reliable palaeoclimatic records in the North and Central-Southern Mediterranean means new evidence is needed to validate this hypothesis. Here, we provide robust quantitative estimates of Holocene climate in the Mediterranean region based on four high-resolution pollen records from Northern (Lakes Ledro and Accesa) and Southern (Lakes Trifoglietti and Pergusa) Italy. Multiple methods are used to provide an improved assessment of the paleoclimatic reconstruction uncertainty. The multi-method approach uses the pollen-based Weighted Averaging, Weighted-Average-Partial-Least-Squares regression, Modern Analogues Technique, and the Non-Metric-Multidimensional Scaling/Generalized-Additive-Model methods. The precipitation seasonality reconstructions are validated by independent lake-level data, obtained from the same records. <br><br> A climatic partition between the north and the south during the Holocene confirms the hypothesis of opposing mid-Holocene summer precipitation regimes in the Mediterranean. During the early-to-mid-Holocene the northern sites (Ledro, Accesa) are characterized by minima for summer precipitation and lake-levels while the southern sites (Trifoglietti, Pergusa) are marked by maxima for precipitation and lake-levels. During the late Holocene, both pollen-inferred precipitation and lake-levels indicate the opposite pattern, a maximum in North Italy and a minimum in Southern Italy/Sicily. Summer temperatures also show partitioning, with warm conditions in Northern Italy and cool conditions in Sicily during the early/mid-Holocene, and a reversal during the Late-Holocene. <br><br> Comparison with marine cores from the Aegean Sea suggests that climate trends and gradients observed in Italy shows strong similarities with those recognized from the Aegean Sea, and more generally speaking in the Eastern Mediterranean

Pollen-based reconstruction of Holocene vegetation and climate in southern Italy: the case of Lago Trifoglietti

“…Therefore, it is preferable to discuss in terms of trend instead of raw values. The climate trend reconstructed at Lago Trifoglietti during the Holocene is consistent with closest sites such as Lake Preola in Sicily (see Peyron et al, 2012) and with the estimates obtained for a marine core located in the Gulf of Salerno (Fig. 9c) by Di Donato et al (2008).…”

“…11 200 cal BP (Fig. 9f, see also Peyron et al, 2012), MAT annual precipitation reconstructed at Trifoglietti illustrates a marked drying phase (500 mm yr −1 ).…”

“…This more humid phase favours beech/fir forest restoration (despite relative instability) and corresponds to peaks in annual precipitation ( Fig. 9f; Peyron et al, 2012). The drop in AP wa is linked to frequent occurrences of Rumex, Chenopodiaceae and Plantago which suggest pastoral activities in the surrounding forests.…”

“…9f. Winter and summer precipitations are also reconstructed and discussed in the paper of Peyron et al (2012) which propose a climatic reconstruction based on a multi-method approach (MAT, WA, WAPLS, NMDS/GAM) on four Italian pollen records (Lakes Ledro, Accesa, Trifoglietti, Pergusa). More details on the methods and their application to Trifoglietti's pollen record are given in this paper.…”

Climate and vegetation changes during the Lateglacial and early–middle Holocene at Lake Ledro (southern Alps, Italy)

“…The biomes assigned to the selected modern analogues are compared to the biome assigned to the fossil assemblage, and only the analogues with consistent biomes are retained for the analogue matching step. Additional information about MAT methodology and its application to the Ledro pollen record are available in the work by Peyron et al (2012). Annual precipitation was reconstructed based from the pollen dataset (dashed line in Fig.…”