Dr. Vera Schiebel

 

Dissertation Title

Vegetation and climate history of the southern Levant during the last 30,000 years based on palynological investigation

Supervisor: Prof. Dr. Thomas Litt
Advisor: Prof. Dr. Andreas Hense

Abstract

Paleo-vegetation of northern Israel is reconstructed from palynological data over the Late Pleistocene and Holocene, and related to climate variation in the Levant, as well as anthropogenic impact on vegetation.

Being located in the arid-to-semi-arid climatic transitional zone, the modern and past vegetation in northern Israel comprises both, Mediterranean macchia, and Irano-Turanian steppe assemblages, and thus is highly sensitive to climate change. Palynological analyses were carried out on two lacustrine sediment profiles obtained during drilling campaigns, at Lake Kinneret in northern Israel (17.8 m composite core length), and at Birkat Ram in the Golan Heights (10.96 m composite core length). A chronological model was developed for both profiles based on radiocarbon dates. Variations in the composition of pollen assemblages were recorded.

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Spanning ~30,000 years, and thus reaching further back than any other record in the southern Levant, the new Birkat Ram pollen record reflects predominating steppe vegetation indicating dry and cold climatic conditions during the Pleniglacial and the Last Glacial Maximum (23,000-19,000 cal BP). Deposition of sediments was very low and even discontinuous during the Late Glacial from around 17,000 cal BP to ~10,000 cal BP suggesting low lake levels to the point of desiccation of Birkat Ram by increased evaporation. Distinct peaks of Artemisia and Chenopodiaceae pollen yet reflect a characteristic eastern Mediterranean Younger Dryas-pattern (12,900

Alumni Schiebel map

(a) Map of Israel and adjacent areas showing relevant cities (•), rivers, and mountains (▲); (b) Birkat Ram, red star indicates coriing site; (c) Lake Kinneret including bathymetric data after Sade et al. (2008), red star indicates coring site

-11,700 cal BP) in the Birkat Ram pollen record. A conspicuous increase of Mediterranean taxa is slightly delayed, and occurs after the onset of the Holocene (~11,700 cal BP) reflecting increased precipitation. There is strong evidence that the ‘8.2 ka Climate Event’ can be verified in the Birkat Ram pollen record. A sharp decrease of Mediterranean taxa indicates distinct deterioration of climatic conditions.

The Lake Kinneret pollen record encompasses the past ~8,000 years. Moderately low ratios of Mediterranean taxa indicate relatively dry conditions from the bottom of the profile, and which slightly change to mesoclimatically more favoured condition until 6,500 cal BP. The Birkat Ram record, on the contrary, is characterised by high values of Mediterranean vegetation assemblages reflecting higher availability of precipitation in the Golan Heights over the entire early Holocene.

Increased ratios of olive pollen both from Birkat Ram and Lake Kinneret point to periods of enhanced human interference with vegetation between ~6,500 and ~4,700 cal BP (Chalcolithic period – Early Bronze Age), and between ~2,200 and ~1,500 cal BP (Hellenistic – Roman / Byzantine period). Regeneration of the vegetation after the first wave of olive cultivation was predominated by high-stemmed deciduous oaks whereas abandoned areas after the second wave of olive cultivation were re-occupied by multi-stemmed evergreen oaks which are less vulnerable for anthropogenic impact (e.g., grazing, logging) than deciduous oaks. From 19th to 20th century, pollen assemblages at Birkat Ram and Lake Kinneret pollen record indicate Pine afforestation, and the introduction of Eucalyptus and Casuarina being Neophytes from Australia.

The results of this study contribute to the discussion on temporal and geographical occurance of vegetation changes, as well as settlement periods in the Levant, and improve the data base for a better understanding of the development of vegetation changes over the climatically variable transition from Late Pleistocene to the Holocene. In addition, understanding interdependencies of past societies and their environments is indispensable to better asses and develop strategies for agriculture and food production during times of environmental and climate change, in particular in highly climate-sensitive areas such as the Levant.

 

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