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Titre : Anthrakologische Untersuchungen zur Vegetationsgeschichte des Kaokolandes, Nordwest-Namibia.

Anthracological investigations concerning the vegetation history of northwestern Namibia

Auteur : Eichhorn, Barbara

Université de soutenance : Universität zu Köln

Grade : Doctoral 2002

Résumé
With the aim to contribute to the knowledge of the late Quaternary vegetation history of northwestern Namibia, charcoal analyses have been conducted on material originating from rock shelters in different vegetation zones of Kaokoland. Before, a reference collection of wood samples had to be established resulting in a wood anatomical character list and a dichotomous key of the represented species. The research area, presently inhabited by the pastoral nomadic Himba and Herero people, is characterised by a strong east-west climatic gradient influencing the present distribution of vegetation zones. Up to now, little has been known about the Holocene and late Pleistocene vegetation history of Namibia. Pollen as well as archaeobotanical data are generally few and are not available for the northwestern part of Namibia. Due to the arid climate of the region, pollen preserving sediments are scarce. Available data from marine pollen profiles, originating from off the northwest Namibian coast, yield general information on the environmental history of the whole southwestern part of the African continent. However, they cannot contribute to the vegetation history of northwestern Namibia on a regional to local scale. Charcoal preservation in Holocene and partly in terminal Pleistocene layers of rock shelters in the Kaokoland is good. Provided that sediments are undisturbed, charcoal analysis from those sites is an appropriate means of gaining knowledge on the vegetation and climate history of the region. Anthracological analyses from sites in eastern Kaokoland indicate the absence of Colophospermum mopane-savanna and dominance of the genus Acacia in the terminal Pleistocene woody vegetation. Temperatures as well as precipitation during that period were most probably lower than at present. Charcoal analytical data concerning the Early Holocene originate from site Omungunda in the eastern higher rainfall region. The presence of a mopane savanna can already be assumed during that period. However, the absence of woody taxa typical for the present �Spirostachys africana-Colophospermum mopane tree savanna� during the Early Holocene indicates distinctly drier conditions. Mid- and Late Holocene charcoal deposits in rock shelters of Kaokoland show little fluctuation in woody species composition and in their relative abundances. Both factors indicate relatively stable environmental conditions during that period. Species typical for each different site can be detected in the charcoal spectra corresponding to the presently surrounding vegetation units. Their site-specific, stable occurrence is a hint that during the Late Holocene environmental conditions remained relatively constant. The proof of Colophospermum mopane type in the charcoal assemblage of site N 2000/1 in the western, arid part of Kaokoland might indicate slightly more humid conditions around 2000 BP. Another wet fluctuation in the Midholocene can be deduced from anthracological results from a site in northwestern Kaokoland. In addition to the anthracological analyses, interviews were conducted with the aim to get information on the influence of selective firewood choice on the archaeobotanical samples. The results indicate that wood collection is selective, but changes with the vegetation zones along the climatic gradient. Thus, in this special case, the influence of anthropogenic selection on archaeobotanical data can be considered as limited.

Mots clés  : Vegetationsgeschichte , Namibia , Mopanesavanne , Holzkohle , Kaokoland — vegetation history , mopane savanna , Namibia , charcoal , Kaokoland

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