Résumé
Mountain regions of North Africa and the Mediterranean represent one of the hotspots of current climate change, where increasing temperatures and drought stress may lead to significant changes in hydrological, ecological and geomorphological systems. Palaeoecological records can provide insights into the responses of montane systems to climate changes, with the impacts of rapid (centennial-scale) responses being of particular relevance. Here, we present the first results of high resolution ( nearly equal 40-50 yr) palynological and charcoal analyses as part of a multiproxy palaeoecological and palaeolimnological study of new lake sediment cores recovered from Lake Sidi Ali in the Middle Atlas mountains, Morocco (33 degrees 03 N, 05 degrees 00 W; 2,080 m a.s.l.). Focusing on the relatively poorly known early Holocene and early to mid-Holocene transition, we provide evidence for pseudo-cyclic centennial-scale changes in vegetation cover and composition, superimposed on the long-term transition from oak (Quercus spp.) dominated early Holocene vegetation to cedar (Cedrus atlantica) forest of the mid-Holocene. In the context of the intermediate position of the Middle Atlas mountains with respect to the influence of mid-latitude, moisture-bearing air-masses and low-latitude, southerly, Saharan air-masses, this early Holocene variability in vegetation cover is interpreted in terms of dynamics shifts in prevailing atmospheric circulation over this montane region of Northwest Africa. The geographical position of the record is ideal for testing patterns of climate variability previously detected in western Mediterranean marine sequences, and for evaluating linkages between mid- and low-latitude climate dynamics.