Spatio-temporal patterns of Holocene environmental change in southern Sicily

Abstract

Few examples of natural forest remain near the Mediterranean coast. Therefore, it is difficult to study how coastal forests respond to climatic change or their resilience to human impact. We developed new sedimentary record of Holocene vegetation and fire history at Lago Preola, a coastal lake in southwestern Sicily (Italy). In order to verify the existence of forest at large scale on the coast, we compare pollen from Lago Preola, a medium-sized lake (33 ha), to Gorgo Basso, a small lake (3 ha) located nearby with the aim of separating local from extra-local vegetation dynamics through time using pollen percentages and influx. We then compare Lago Preola pollen to the record from Biviere di Gela, a large lagoon (120 ha) situated 160 km to the east in southern Sicily, to examine differences in vegetation dynamics between the two coastal areas during the Holocene. Lake-level reconstructions and ostracode analyses from Lago Preola provide vegetation-independent evidence of climate change, and help to disentangle human and climatic impacts on vegetation. Pollen data indicate Pistacia-dominated shrublands replaced open grasslands in the region surrounding Lago Preola by 9500 cal yr BP. This change coincided with rising lake levels and the development of an ostracode fauna typical of fresh waters. Evergreen forest dominated by Quercus ilex and Olea europaea started to expand by 7000 cal BP and consolidated at 6500 cal yr BP, when lake levels were near their Holocene high. Similarities between pollen from Lago Preola and Gorgo Basso demonstrate that forest was the dominant vegetation type in coastal Sicily during the middle Holocene at both regional and local scales, and even developed in the drier climatic setting around Biviere di Gela. Lake levels fell at Lago Preola after 7000 cal yr BP, with a strong decline accompanied by increasing salinity after 4500 cal yr BP. However, no transition in vegetation matched these inferred hydrological changes. Instead, forests persisted in the surrounding region until 2200 cal BP when human disturbance intensified. We propose that different climatic factors control lake levels and vegetation in coastal Mediterranean ecosystems. Whereas lake levels are most sensitive to the abundance of winter precipitation, coastal forests depend on spring precipitation and are limited by the length of summer drought. Moisture availability remained suitable for evergreen forests in coastal Sicily during the late Holocene, and humans, not a drier climate drove the regional forest decline.

Holocene environmental history of a small Mediterranean island in response to sea-level changes, climate and human impact

“…(Gorgo Basso and Lago Preola, respectively sites 5 and 6 in Fig. 1; Calò et al, 2012;Tinner et al, 2009). More generally if the clearance of Erica arborea vegetation is recorded everywhere on Corsica Island from coastal sites (Reille, 1984(Reille, , 1988b(Reille, , 1988c(Reille, , 1992a to high altitude (until 1500 m; Reille, 1975Reille, , 1988aReille et al, 1999), the chronological framework of this decline has to be refined and compared with the archaeologogical evidence to evaluate the synchronicity or discrepancy of this active phase, but we also need to evaluate the role that Neolithic societies could have played in these dynamics.…”

“…on coastal areas was also interpreted as the result of an increase of moisture availability (during summer and winter) in Sicilia (Calò et al, 2012;Noti et al, 2009;Tinner et al, 2009) and Malta (BM1 and BM2 sediments cores, respectively sites 9…”

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“…Most of the landscape surrounding the reserve is managed for agriculture, including vineyards, olive groves, and orchards. Several rare species occur in the aquatic and hygrophilous communities of the reserve, such as Cladium mariscus, Juncellus laevigatus, Damasonium bourgaei, Galium elongatum and Hypericum tetrapterum (Calò et al, 2012). Halophyte species, including Arundo donax L. and Arthrocnemum macrostachyum (Moric.…”

The likely impact of climate change on the biodiversity of Italian forests

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Il cambiamento climatico (CC) influenza in modo significativo la biodiversità forestale, sia negli aspetti che riguardano la distribuzione delle specie, i loro processi di migrazione e la loro variabilità genetica, sia in quelli che riguardano la fisionomia e la struttura delle biocenosi forestali, con ricadute anche alle scale più complesse di ecosistema e paesaggio.Conoscenze utili, al fine di formulare previsioni orientative, possono essere ricavate da studi paleoecologici e filo-geografici, con particolare riferimento alla risposta delle specie arboree ad antecedenti variazioni climatiche, in termini di capacità di adattamento e migrazione (ad es., Petit et al 2005, Svenning et al 2008, Calò et al 2012. A tale riguardo, sono note sia le principali rotte di migrazione postglaciale, sia le maggiori aree di rifugio inter-glaciale di numerose specie forestali europee.

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“…Conoscenze utili, al fine di formulare previsioni orientative, possono essere ricavate da studi paleoecologici e filo-geografici, con particolare riferimento alla risposta delle specie arboree ad antecedenti variazioni climatiche, in termini di capacità di adattamento e migrazione (ad es., Petit et al 2005, Svenning et al 2008, Calò et al 2012. A tale riguardo, sono note sia le principali rotte di migrazione postglaciale, sia le maggiori aree di rifugio inter-glaciale di numerose specie forestali europee.…”