Vegetation dynamics, palaeoenvironments and climatic changes in the forests of western Cameroon during the last 28,000 years B.P.

摘要: The lake Barombi Mbo pollen record goes back to about 28,000 yr B.P. diagram based on 82 samples is subdivided into four main zones. Zone I (ca. 20,000 B.P.) characterized by relatively high frequencies of Caesalpiniaceae and also a montane element with Olea capensis. climate was cool wet. II 10,000 B.P.). A sharp increase in Gramineae, the non-arboreal land taxon, began around lasted until During this period forest receded, giving way more open vegetation, but significant patches (refuges) persisted area. This confirmed isotopic analyses (δ13C sedimentary detritic organic matter from catchment. Until ca. 13,000 capensis well represented indicating climate. Between 12,000 warming trend associated strong precipitation occurred. After an abrupt reduction linked seasonality, without temperature lowering, intervened between 11,500 10,400 last phase corresponds partly Younger Dryas time period. III 2800 became very wet 3000 decrease Gramineae at B.P.; 9500 they remained low, 0 3%, trees reached their maximum extension. Most exhibited large variations quasi-periods 1000 mainly 2000 2200 calendar years), which could be related sylvigenetic or successional cycles. In zone were represented, extension 4500 Podocarpus, typical tree stratiform cloud forests, low before relative during early middle Holocene can only explained its growth distant mountains. Its roughly synchronous that Caesalpiniaceae. warm wet, cooler IV present time). Around peaking 30 40% total 2500 B.P., indicates sudden vegetation opening retreat, accompanied severe erosion. Alchornea, pioneer increased rapidly same because it develops abundantly all openings. Elaeis guineensis, originally palm tree, follows pattern. warm, dry, seasonality. returned frequencies, 10%, trees, expanded again not extent as Holocene. rather similar present-day