Vegetation changes during the past 1300 years in western equatorial Afnrca: a highresolution pollen record from Lake Kamalee,Lope Reserve,Central Gabon
Restricted accessResearch articleFirst published online November, 2005
Vegetation changes during the past 1300 years in western equatorial Afnrca: a highresolution pollen record from Lake Kamalee,Lope Reserve,Central Gabon
Vegetation changes during the past 1300 years are reconstructed in western equatorial Africa using a high-resolution pollen record from Lake Kamalete This small marshy basin (c. 5-7 ha) is located in forest-savanna mosaic in Lope Reserve (043'S, 116'E), central Gabon. The Kamalete pollen data show the persistence over the past 1300 years of a relatively stable forest-savanna mosaic, associated with significant changes of the forest component. Three successive stages of forest dynamics occurred. First, at 1325 cal. BP, moist semi-evergreen rainforest existed around the catchment of Lake Kamalete. However, it appears from the consistent presence of > 70% Gramineae pollen that the site was always primarily in savanna. Secondly, from c. 1240 to 550 cal BP, a noticeable increase in shade-intolerant plant species indicate openings in the rainforest canopy. The persistence of gap-colonizer species, such as Macaranga, Tetrorchidium and Musanga for several centuries in the rainforest, is explained by recurring canopy disturbance associated with shifts in available moisture. These hydrological changes may be related to a succession of longer and more severe dry seasons than observed today. Thirdly, at 550 cal BP, mature forest was re-established, corresponding to progressive savanna colonization by forest pioneer species such as Aucoumea klaineana, Lophira alata and Fagara macrophylla. This new phase of forest expansion coincided with a marked lithological change, indicating an increase in lake-level. It is concluded that the major vegetation changes observed are due to climatic variability, and anthropogenic action had limited influence.
Assemien, P. , Bonnefille, R. , Cambon-Bou, G. , Caratini, C. , Cerceau, M.T. , Dang, C.D. , Fredoux, A. , Guers, J. , Guinet, P. , Hideux, M. , Hul-Thol, S. , Keddam-Malplancha, M. , Le, T.A. , Lobreau-Callen, D. , Lugardon, B. , Maley, J. , Mallea, M. , Masure, E. , Medus, J. , Nigard, M. , Riollet, G. , Senesse, S. , Sivak, J. , Soler, M. , Stainer, F. , Thanikaimoni, G. and Thiam, A.1974: Pollen et Spores d'Afrique tropicale. Bordeaux: Association des Palynologues de Langue Francaise , 283-283 pp.
2.
Aubreville, A.1967: Les etranges mosaiques foret-savanes du sommet de la boucle de l'Ogooue au Gabon . Adansonia7, 13-22 .
3.
Baker, J.C. , Kassan, J. and Hamilton, P.J.1995: Early diagenetic siderite as an indication of depositional environment in the Triassic Rewan Group, southern Bowen, eastern Australia . Sedimentology43, 77-88 .
4.
Barret, J.1983: Geographie et Cartographie du Gabon. Paris: EDICEF , 135135 pp.
5.
Bonnefille, R. and Riollet, G.1980: Pollens des savanes d'Afrique orientale. Paris: Centre National de Recherche Scientifique , 130-130 pp.
6.
Bradley, R.2000: 1000 years of climate change . Science288, 13531353 .
7.
Broecker, W.S.2001: Was the Medieval Warm Period global?Science291, 1497-1499 .
8.
Bush, M.B.2002: On the interpretation of fossil Poaceae pollen in the lowland humid neotropics . Palaeogeography, Palaeoclimatology, Palaeoecology177, 5-17 .
9.
Clist, B.1995: Gabon: 100 000 ans d'Histoire. Libreville: Centre Culturel Franqais Saint-Exupery (Gabon) , 376376 pp.
10.
de Foresta, H.1990: Origine et evolution des savanes intramayombiennes (R.P. Congo). II. Apport de la dynamique forestiere. In Lanfranchi, R. and Schwartz, D. , editors, Paysages Quaternaires de l'Afrique centrale Atlantique. Paris; ORSTOM326-335.
11.
Descoings, B.1974: Les savanes du Moyen-Ogooue, region de Booue (Gabon). Montpellier: Centre National de Recherche Scientifique .
12.
Elenga, H. , Schwartz, D. and Vincens, A.1992: Changements climatiques et action anthropique sur le littoral congolais au cours de l'Holocene . Bulletin de la Soci&et Geologique de France163, 239-252 .
13.
Elenga, H. , Schwartz, D. and Vincens, A.1994: Pollen evidence of Late Quaternary vegetation and inferred climate changes in Congo . Palaeogeography, Palaeoclimatology, Palaeoecology109, 345-356 .
14.
Elenga, H. , Schwartz, D. , Vincens, A. , Bertaux, J. , de Namur, C. , Martin, L. , Wirrmann, D. and Servant, M.1996: Diagramme pollinique holocene du Lac Kitina (Congo): mise en evidence de changements paleobotaniques et paleoclimatiques dans le massif forestier du Mayombe . Compte-Rendu de l'Academie des Sciences, Paris, serie 2a323, 345-356 .
15.
Faegri, K. and Iversen, J.1975: Text book of modern pollen analysis. Oxford: Blackwell , 295295 pp.
16.
Florence, J. 1981: Chablis et sylvigenese dans une foret humide sempervirente du Gabon. Ph.D. Thesis, Universite Louis Pasteur, Strasbourg, 261 pp.
17.
Flore du Gabon1962-1995: Museum National d'Histoire Naturelle, Paris .
18.
Giresse, P. , Maley, J. and Brenac, P.1994: Late Quaternary paleoenvironments in Lake Barombi Mbo (West Cameroon) deduced from pollen and carbon isotopes of organic matter . Palaeogeography, Palaeoclimatology, Palaeoecology107, 65-78 .
19.
Goeury, C.1988: Acquisition, gestion et representation des donnees de l'analyse pollinique sur micro-ordinateur . Institut FranVais Pondichery Travau Section Sciences et Techniques25, 405-416 .
20.
Haug, G.H. , Hughen, K.A. , Sigman, D.M. , Peterson, L.C. and Rohl, U.2001: Southward migration of the Intertropical Convergence Zone through the Holocene . Science293, 1304-1308 .
21.
Jolly, D. , Bonnefille, R. , Burcq, S. and Roux, M.1996: Representation pollinique de la foret dense humide du Gabon, tests statistiques . Compte-Rendu de l'Academie des Sciences, Paris, s&rie 2a322, 63-70 .
22.
Kelts, K. and Talbot, M.1990: Lacustrine carbonates as geochimical archives of environmental change and biotic/abiotic interactions. In Tilze, M. M. and Serruya, C. , editors, Ecological structure and function in large lakes. Madison WI: Science and Technology Publishers , 290-317.
23.
Lamb, H. , Darbyshire, I. and Verschuren, D.2003: Vegetation response to rainfall variation and human impact in central Kenya during the past 1100 years . The Holocene13, 285-292 .
24.
Leroux, M.1983: Le climat de l'Afrique tropicale. Paris: Champion , 633633 pp.
25.
Letouzey, R.1968: Etude Phytogeographique du Cameroun. Paris: Paul Lechevallier , 511511 pp.
26.
Maley, J.1997: Middle Holocene changes in tropical Africa and other continents: paleomonsoon and sea surface temperature variations. In Dalfes, H.N. , Kukla, G. and Weiss, H. , editors, Third millennium BC climate change and old world collapse. NATO ASI Series. Berlin, Heidleberg: Springer-Verlag , 611-640.
27.
Maley, J.1999: L'expansion du Palmier a Huile (Elaeis guineensis) en Afrique centrale au cours des trois derniers millenaires: nouvelles donnees et interpretations. In Bahuchet, S. , editor, L'Homme et la Foret Tropicale. Marseille: Travaux de la Societe d'Ecologie Humaine , 237-254.
28.
Maley, J. and Brenac, P.1998: Vegetation dynamics, paleoenvironments and climatic changes in the forests of western Cameroon during the last 28,000 years B.P.Review of Palaeobotany and Palynology99, 157-187 .
29.
Maley, J. and Chepstow-Lusty, A.2001: Elaeis guineensis Jacq. (oil palm) fluctuations in central Africa during the late Holocene: climate or human driving forces for this pioneering species?Vegetation history and Archaeobotany10, 117-120 .
30.
Maley, J. , Giresse, P. , Makaya, M. , Ngomanda, A. , Oslisly, R. , Rabenkogo, N. , Jolly, D. , Fontugne, M. , Bentaleb, I. , Moeyersons, J. , Doutrelepont, H. , Stager, C. and Ariztegui, D.2001: PALEOFORGA, a new research program on the late Quaternary palaeoenvironments in Gabon, Central Africa. In Past climate variability trough Europe and Africa. Aix en Provence: PAGES & Pole to Pole/3 , 117-118.
31.
Nguetsop, V.F. , Servant-Vildary, S. and Servant, M.2004: Late Holocene climatic changes in west Africa, a high resolution diatom record from equatorial Cameroon . Quaternary Science Reviews23, 591-609 .
32.
Nicolas, P. 1977: Contribution a l'Etude Phytogeographique de la Foret du Gabon. Ph.D. Thesis, Universite de Paris 1, Paris, 260 pp.
33.
Osborne, P.L.2000: Tropical ecosystems and ecological concepts. Cambridge: Cambridge University Press , 464464 pp.
34.
Oslisly, R.1995: The middle Ogooue valley, Gabon: cultural changes and palaeoclimatic implications of the last four millenia . AzaniaXXIX-XX, 324-331 .
35.
Oslisly, R.1998: Hommes et milieux a l'Holocene dans la moyenne vallee de l'Ogooue (Gabon) . Bulletin de la Societe Geologique de France95, 93-105 .
36.
Oslisly, R.2001: The history of human settlement in the Middle Ogooue Valley (Gabon). In Weber, W , White, L.J.T. , Vedder, A. and Naughton-Treves, L. , editors, African rain forest ecology and conservation. New Haven CT, London: Yale University Press , 101-118.
37.
Puig, H.2001: La Foret Tropicale Humide. Paris: Belin , 448448 pp.
38.
Reynaud, I. and Maley, J.1994: Histoire recente d'une formation forestiere du sud-ouest du Cameroun a partir de l'analyse pollinique . Compte-Rendu de l'Academie des Sciences, Paris, s&rie 2a337, 575-580 .
39.
Reynaud-Farrera, I. , Maley, J. and Wirrmann, D.1996: Vegetation et climat dans les forets du Sud-Ouest Cameroun depuis 4770 ans B.P: analyse pollinique des sediments du Lac Ossa . Compte-Rendu de l'Academie des Sciences, Paris, s&rie 2a322, 749-755 .
40.
Riera, B. and Alexandre, D.Y.1988: Surface des Chablis et temps de renouvellement en foret dense tropicale . Acta Oecologica9, 221-230 .
41.
Saint-Vil, J.1977: Les climats du Gabon . Annales de l'Universite nationale du Gabon1, 101-125 .
42.
Schwartz, D.1992: Assechement climatique vers 3000 B.P. et expansion Bantu en Afrique Centrale atlantique: quelques reflexions . Bulletin de la Socie& Geologique de France163, 353-361 .
43.
Stuiver, M. , Reimer, P.J. , Bard, E. , Beck, J.W. , Burr, G.S. , Hughen, K.A. , Kromer, B. , McCornac, F.G. , v.d. Plicht, J. and Spurk, M.1998: INTCAL98 Radiocarbon age calibration 24,000-0 cal B.P . Radiocarbon40, 1041-1083 .
44.
Swaine, M.D.1992: Characteristics of dry forest in West Africa and the influence of fire . Journal of Vegetation Science3, 365-374 .
45.
Tutin, C.E.G. and Fernandez, M.1993: Relationships between minimum temperature and fruit production in some tropical forest trees in Gabon . Journal of Tropical Ecology9, 241-248 .
46.
Tutin, C.E.G. , White, L.J.T. , Williamson, E. , Fernandez, M. and McPherson, G.1994: List of plant species identified in the northern part of the Lope Reserve, Gabon . Tropics3, 249-276 .
47.
van der Meer, P.J. and Bonger, F.1996: Formation and closure of canopy gaps in the rain forest at Nouragues, French Guiana . Vegetatio126, 167-179 .
48.
Verschuren, D. , Laird, K.R. and Cumming, B.F.2000: Rainfall and drought in equatorial east Africa during the past 1,100 years . Nature403, 410-414 .
49.
Vincens, A. , Schwartz, D. , Bertaux, J. , Elenga, H. and de Namur, C.1998: Late Holocene climatic changes in Western Equatorial Africa inferred from pollen from Lake Sinnda, Southern Congo . Quaternary Research50, 34-45 .
50.
White, F.1983: Vegetation of Africa. Paris: UNESCO/AETFAT/ UNSO Maps and Memoirs , 356356 pp.
51.
White, L.J.T. 1992: Vegetation history and logging disturbance: effects on rain forest mammals, in the Lope Reserve, Gabon (with special emphasis on Elephants and Apes). Ph.D. Thesis, University of Edinburgh, Edinburgh, 250 pp.
52.
White, L.J.T. 1995: Etude de la Vegetation de la Reserve de La Lope: rapport final du Projet ECOFAC, Composante Gabon. Agres consulting, centre Techniques Forets Tropicales, Wildlife Conservation Society Gabon, 141 pp.
53.
White, L.J.T.2001: Forest-savanna dynamics and the origins of Marantaceae forest in central Gabon. In Weber, W , White, L.J.T. , Vedder, A. and Naughton-Treves, L. , editors, African rain forest ecology and conservation. New Haven CT and London: Yale University Press , 165-182.
54.
White, L.J.T. and Abernethy, K.1997: A guide to the vegetation of the Lope Reserve Gabon. Libreville: ECOFAC GABON , 224224 pp.
55.
White, L.J.T. , Rogers, M.E.R. , Tutin, E.A. and Fernandez, M.1995: Herbaceous vegetation in different forest types in the Lope Reserve, Gabon: implications for keystone food availability . African Journal of Ecology31, 181-199 .
56.
White, L.J.T. , Oslisly, R. , Abernethy, K. and Maley, J.2000: L'Okoume (Aucoumea klaineana): expansion et d&eclin d'un arbre pionnier en Afrique centrale atlantique au cours de l'Holocene. In Servant, M. and Servant-Vildary, S. , editors, Dynamique a long terme des ecosystemes forestiers intertropicaux. Paris: Memoire UNESCO , 399-411.
57.
Wirrmann, D. , Bertaux, J. and Kossoni, A.2001: Late Holocene paleoclimatic changes in Western Central Africa inferred from mineral abundance in dated sediments from Lake Ossa (Southwest Cameroon) . Quaternary Research56, 275-287 .
58.
Ybert, J.-P.1979: Atlas de pollens de Cóte d'Ivoire. Paris: ORSTOM , 4040 pp.
