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Archaeobotany

Within the framework of the Joint Mission, archaeobotanical studies have been carried out by researchers of the Laboratory of Palynology and Palaeobotany of the University of Modena and Reggio Emilia since 1990. Main target of the research is to make an inventory of microscopical and macroscopical botanical records present in the studied contexts with the aim of improving:

• the knowledge of flora and vegetation which lived, especially in the Holocene, in Central Sahara to reconstruct the plant landscape of the area and global climatic oscillations;
• the comprehension of the cultural landscape development in the same period, and of the complex relationships between human beings and environment which occurred in the area.

Many topics were preliminary investigated, and the archaeobotanical research has concentrated so far on the Tadrart Acacus mountains (Wadi Teshuinat and surroundings), on the Early and Middle Holocene chronological phases (between approx. 10.000 and approx. 3500 years bp) and on anthropogenic deposits from rockshelters and caves, firstly occupied by hunter-gatherers and then by pastoral groups. In the future, analyses from lake deposits of the mountains and garamantian sites of the plain will be intensified too.

Acacias (Acacia tortilis var. raddiana): isolated trees in the Wadi Teshuinat	Thorns, up to 15 cm length, and leaves of acacia	Acacia-Panicum community with shrubs of Zilla spinosa, Wadi Istanen

 

Features of the archaeobotanical deposits

When first pollen and fruits from Tadrart Acacus were analysed, the main features of these archaeobotanical deposits promptly emerged

• in the archaeological sites, pollen and macroremains are abundant and preserved in a very well state of preservation
• seeds and fruits, together with many other plant remains, are prevalently in a desiccated state, which prevents flotation, and recommended dry sieving to extract them from sediments
• all the botanical record is an unquestionable witness of a landscape characterised by a large plant cover and with a composition different from the present
• records from aquatic or hygrophilous plants (Cyperaceae, Typha) testify that wet environments were well diffused, also including permanent water flows which spread during the wet climatic oscillations of the Early and Middle Holocene
• the botanical list includes elements of floras currently more diffused northern or southern than the Central Sahara (e.g., respectively genera Artemisia and Urochloa), floras which do not grow together today and which, on the contrary, had lived together in this zone lying between the Mediterranean and the Tropical zones, at least up to approx. 4000 years bp.

Dry sieve extraction for plant macroremains, Takarkori	Pollen of cattail (Typha, max. 40 µm), Early and first Middle Holocene	Pollen of wormwood (Artemisia, max. 22 µm), late Early and Middle Holocene

 

Climate, Plant landscape and Cultures

a long history of landscape evolution …

Between ca. 10000 and 8000 years bp, the plant landscape had a continuous herbaceous cover consisting in a savannah type vegetation (with Brachiaria) alternating with permanent wet environments. Flora and vegetation of the period testify that climate was much more humid and cooler than the present At the end of this period, an increase of dryness forced plants to give a biological answer typical of the mountains: flora becomes more rich in species and vegetation becomes more fragmented. The more articulated plant landscape consists in a mosaic of grassland, shrubland and wet environments, also distributed in altitudinal belts. Some types of vegetation possibly have not modern analogous.

Caryopses of wild cereal (Brachiaria, 2,5x3 mm), Early Holocene

The richness of plant resources, mainly wild cereals, was most probably a striking force to concentrate people in the mountains and to favourite the development of the civilisations of hunter-gatherers which went up to refugium areas from the lowlands, more impoverished of resources during the arid phases.

Between ca. 7000 and 5000 years bp, the plant landscape evolved in a wooded savannah with acacias and other tropical plants, and still a wide spread of wet environments. The climate was humid but probably more hot than previously. The wild cereals became less various but remained quite abundant in the territory. Pastoral groups occupied the area and exploited plant resources in a different way with respect to hunter-gatherers.

Between ca. 5000 and 3500 years bp, wet environments clearly regressed, and the desert savannah with Acacia-Panicum communities, together with psammophilous plants, spread in the region. Vegetation became quite similar to the current but it was decidedly more diffused. Climate became more dry than in the previous phases, but it was not so hyperarid as in the present. The environment under hard climatic conditions became more selective for plants, and this selection was also forced by the recurring ovicaprine grazing.

Uan Muhuggiag: hypothetical reconstruction of the plant landscape in the late Middle Holocene	Uan Muhuggiag in 1992

 

Towards the present landscape…

The evolution of the plant landscape in the Tadrart Acacus has been influenced by both climate and humans:

1. on the one hand, climatic oscillations modified local flora composition and cover; this encouraged humans to have new 'botanical discoveries' and forced their changes in adaptive strategies;
2. on the other hand, and at the same time, human influence on the territory modified the environment; this influence was firstly sensibly marked by plant harvesting and selection, and then more incisively marked by herding.

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