HR: 16:30h
AN: B44C-03    [Abstracts]
TI: High temporal Resolution Fire History in Eastern Africa: the Last 16 kyr cal. BP
AU: * Vanniere, B
EM: boris.vanniere@univ-montp2.fr
AF: CBAE / UMR 5059 CNRS - University of Montpellier II, Institut de Botanique 163 rue Auguste Broussonet F-34090, Montpellier, cedex France
AU: Carcaillet, C
AF: CBAE / UMR 5059 CNRS - University of Montpellier II, Institut de Botanique 163 rue Auguste Broussonet F-34090, Montpellier, cedex France
AU: Garcin, Y
AF: CEREGE / UMR 6635, Europle M‚diterran‚en de l'Arbois -BP 80- 13545, Aix-en-Provence, cedex 04 France
AU: Vullien, A
AF: CBAE / UMR 5059 CNRS - University of Montpellier II, Institut de Botanique 163 rue Auguste Broussonet F-34090, Montpellier, cedex France
AU: Williamson, D
AF: CEREGE / UMR 6635, Europle M‚diterran‚en de l'Arbois -BP 80- 13545, Aix-en-Provence, cedex 04 France
AB: Charcoal series, based on a high temporal resolution analysis, at Lake Massoko (9ø20' S, 33ø 45' E, 770 a.s.l., SW Tanzania) reveals numerous changes of fire regime over the last 16 kyr cal BP. Data are based on the tallying of charcoal from 700 continuous 1 cm thick samples along a 7m long sequence. The structure of charcoal particles is well preserved with an length:width ratio superior to 5; this appears to testify to the local provenance of the material studied and to the rapid transport of particles to the lake. The majority of particles belongs to herbaceous cuticles produced by savanna or bush fires. Time control is supported by 14 radiocarbon dates. Mean time resolution per sample of 17 yr provides the first long detailed biomass burning record in Africa. This record evidences frequent fires events during the last 16 kyr, indicating that fire is a key component of east African ecosystems since, at least, the last glacial stage up to present. From 16 to 12 kyr cal BP, the charcoal influx into the lake is low except during two specific sequences, between 13.5-12.5 kyr cal BP and 14.5-14 kyr cal BP. These may correspond to more arid or more biomass-available phases. Around 10 kyr cal BP, at the early Holocene a greater influx of charcoal is recorded in the lake, probably as a result of a high fire regime likely triggered by severe droughts. Between 8.3 and 1.7 kyr cal BP, the charcoal influx displays a cyclic fire history of ca. 500 yr. Low fire regime, between 3.5-2.5, 5.5-5 and 7.5-7 kyr cal BP, correspond to wetter periods. About 12 sequences of fire increase and decrease are highlighted, which appears to support a high climatic variability during the middle-Holocene. After 1.7 kyr BP, there is a long lasting increase of charcoal influx into the lake, as observed by black carbon analysis (Thevenon et al., 2003). This particular period, without analog since 16 kyr cal BP, is consistent with the development of Iron Age settlements in the region, slash-and-burn agriculture and animal husbandry fire practices. This work was supported by the French CNRS-INSU-FNS, ECLIPSE (CLEHA) and RESOLVE programs.
DE: 9305 Africa
DE: 3344 Paleoclimatology
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting