An 18,000-Year Record of Vegetation, Lake-Level and Climatic Change from Tigalmamine, Middle Atlas, Morocco

Pollen, stable istotope and sedimentological analyses of a 21 m-long radiocarbon-dated core of calcareous lake sediments from the Middle Atlas mountains, Morocco, provcide an 18,000-year record of change in lake level and local vegetation attributable to climatic, ecological and anthropogenic causes. Herb-rich grassland persisted for nearly 10,000 years, except for a period between 14,000 and 12,000 BP when scattered oaks were present. Oak forest replaced the grassland 8500 years ago and Cedrus atlantica (Endl.) Carriere arrived in the area about 4000 years ago. These vegetation changes probably resulted from increased available moisture. The water level, in what must formerly have been a steep-side doline, rose substantially at 8500 BP, and again by at least 2 m at 1500 BP. Coincidence of vegetational and lake-level change sugests that establishing tree populations were derived from local sources. Anthropogenic forest degradation dates from about 2250 BP. In spite of this, the Cedrus forests became more vigorous about 450 years ago.