Late Quaternary peat formation and vegetation dynamics in a lowland tropical swamp; Nee Soon, Singapore

Cores of sediment from Nee Soon, a peat-forming freshwater swamp located in the perimarine zone of Singapore, have yielded a record of vegetation hist ory that comprises parts of the last glacial and Holocene periods. The evid ence includes two conventional and four AMS radiocarbon dates, the oldest o f which is 23,050 +/- 330 B.P. (uncalibrated radiocarbon years), and variat ions in the abundances of sub-fossil pollen and spores and charcoal. The re sults of a study of the relationship between contemporary vegetation and mo dem pollen accumulation facilitated interpretation of sub-fossil tree polle n data. Peat formation occurred at Nee Soon during the last glacial, when s ea levels on the Sunda continental shelf were well below those at present. The occurrence of montane pollen types, notably Podocarpaceae, in sediment samples dated to the late glacial and early Holocene suggests either temper atures substantially lower than those of the present and, possibly, humid c onditions, or cold, seasonally dry climates and reduced levels of atmospher ic CO2. The abundance, of charcoal indicates the widespread occurrence of f ires throughout the entire period represented by the cores. For the mid Hol ocene, the evidence indicates an increased saline influence, presumably as a result of relatively high sea levels. Falling sea levels during the late Holocene appear to have preceded the onset of the most recent period of pea t formation at Nee Soon. The evidence confirms that long (last glacial-inte rglacial) records of lowland vegetation history are available from terrestr ial locations in the humid core of Southeast Asia and suggests that the com plexity of perimarine swamp dynamics is not captured fully by Anderson's mo del, which assumes a close relationship between peat formation and sea leve l. (C) 2001 Elsevier Science B.V. All rights reserved.