Mid-Holocene vegetation history of the central Mediterranean

Abstract

This paper provides a synthesis of available palynological data from central Mediterranean lacustrine records, studying the causes of the important vegetation changes which occurred in the mid Holocene. They are illustrated by seven well-dated records, lakes Accesa, Mezzano, Vico, and Pergusa in Italy, Maliq, Voulkaria and Malo J. in the Balkans. A good tool for disentangling climate change and human impact is the combined interpretation of pollen percentage and concentration/influx data. Pollen concentration/influx drops are an indication of increased erosion in the catchment, mainly ascribable to forest reduction. There is no doubt that major synchronous changes could not have been caused by humans alone. Many southern European records show substantial differences between early- and late-Holocene vegetation, suggesting a general evolution from wetter to drier climatic conditions, in agreement with arid phases recognised by other, independent palaeoclimatic methods. Other pollen records show a different trend. The role of changing seasonality seems important for this region of the Mediterranean. Precipitation seasonality increased during the early to mid Holocene with winter precipitation attaining a maximum, and summer precipitation a minimum. At least three rapid climate events with changes in plant biomass are in evidence: an abrupt and short change around 8200 yr BP, another one centred around 6000 yr BP, and one soon after 3000 yr BP. From the beginning of the Bronze Age (c. 4400 yr BP in this region) human impact overlapped with a climate change, probably bipartite, towards dryness. Our results show that this aridification trend began around 8000 yr BP, and culminated around 4000 yr BP

Holocene vegetation and climate changes in the central Mediterranean inferred from a high-resolution marine pollen record (Adriatic Sea)

“…Olea, the emblematic plant of the Mediterranean area, occurs weakly at the beginning of the Holocene and remains sporadic up to 6000 cal yr BP, generally associated only with warming climate. After 6000 cal yr BP Olea is continuously present but is most abundant in the upper part of the record, around 3000 cal yr BP, in agreement with the central Mediterranean vegetation history proposed by Sadori et al (2011) using continental records. Olea is present in marine records across the Mediterranean at this time (e.g.…”

“…This coincides with the decreasing abundance of deciduous trees, especially deciduous Quercus and the increase in herbs such as Asteraceae and steppic taxa (Artemisia excluded) at 3500 cal yr BP. This pattern has been observed elsewhere in the central Mediterranean (Sadori et al, 2011) and marks a shift in the precipitation regime, with decreasing summer precipitation and a progressive establishment of the modern Mediterranean climate (Figs. 3, 4).…”

“…Although it begins at an older age in the MD 90-917 marine core, such a spread of temperate taxa may be related to what is observed in several pollen sequences across the central Mediterranean (e.g. Watts et al, 1996;Sadori and Narcisi, 2001;Allen et al, 2002;Sadori et al, 2011;Di Rita et al, 2013) and corresponds to the Preboreal (PB) improvement at the Younger Dryas/Holocene transition (Björk et al, 1996). Forest expansion is interrupted by a strong drop in arboreal taxa around 11700 cal yr BP, marked by an increase in herbaceous taxa (Asteroideae and Cichoriodeae) and semi-desert taxa, excluding Artemisia (Fig.…”

Holocene climate aridification trend and human impact interrupted by millennial- and centennial-scale climate fluctuations from a new sedimentary record from Padul (Sierra Nevada, southern Iberian Peninsula)

“…Palynological analysis (pollen and NPP) is commonly used as a proxy for vegetation and climate change, lake level variations, human impact, and land use (e.g., van Geel et al, 1983;Faegri and Iversen, 1989). Disentangling natural vs. anthropogenic effects on the environment in the last millenniums is sometimes challenging but can be achieved using a multiproxy approach (Roberts et al, 2011;Sadori et al, 2011). In this study, we used the variations between Mediterranean forest taxa, xerophytes, and algal communities for paleoclimatic variability and the occurrence of nitrophilous and ruderal plant communities and some NPPs for identifying human influence in the study area.…”

Holocene climate variability, vegetation dynamics and fire regime in the central Pyrenees: the Basa de la Mora sequence (NE Spain)

“…documented in vegetation distribution (Jalut et al, 2009;Sadori et al, 2011), lake levelsare directly related to the North Atlantic Oscillation (NAO) that principally determinesidentification was carried out using an optical microscope (Olympus CX41) at 40x 268 magnification and Cell B Imaging Software for Life Science Microscopy (Olympus). 269…”