Influence of rainfall seasonality on African lowland vegetation during the Late Quaternary: pollen evidence from Lake Masoko, Tanzania

Vincens, Annie; Garcin, Yannick; Buchet, Guillaume

doi:10.1111/j.1365-2699.2007.01698.x

Cited by 83 publications

(64 citation statements)

References 68 publications

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“…The presence of these taxa in the pollen record would thus be expected if the Afromontane forest had spread to lower altitudes than it currently occupies and its pollen did not need to be transported over long distances. Therefore, the high pollen abundances of the Afromontane forest in the marine pollen record corroborate previous pollen records that suggest the development of Afromontane taxa at a lower elevation (Vincens et al, 2007b, Ivory et al, 2012 due to freezing conditions at higher altitudes, cooler conditions at lower altitudes and lower pCO 2 (Street-Perott, et al, 1997;Wu et al, 2007). During the decline of the Afromontane taxa, the pollen representatives of dry wood and shrub vegetation increase significantly between ∼ 16.6 and 14.8 kyr BP (Fig.…”

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinsupporting

confidence: 87%

“…7a). A similar vegetation trend has been recorded in several pollen records from lakes Malawi, Tanganyika, Rukwa and Masoko, indicating the retreat of the Afromontane vegetation to higher altitudes due to progressive warming after H1 and the expansion of moist forest due to enhanced rainfall (Vincens, 1993;Vincens et al, 2005Vincens et al, , 2007bIvory et al, 2012). Between ∼ 12.8 and 11.6 kyr BP, the presence of elements from both the forest and humid woodland vegetation and from dry woods and shrubs (Fig.…”

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinsupporting

confidence: 80%

“…We thus infer a shift towards more humid conditions. Significant increase in moisture after ∼ 14.8 kyr BP has been reported from vegetation records in continental archives (Vincens, 1993;Vincens et al, 2005Vincens et al, , 2007bIvory et al, 2012) as well as from lake records (Gasse, 2000;Junginger et al, 2014). Taken together, upland aridity during H1 and the increased humidity around 14.8 kyr BP as reconstructed from our records correlate (within age model uncertainties) with changes inferred from continental archives that show a similar pattern in most of the tropical eastern and southeastern African lakes and are in agreement with northwest tropical African records (e.g., Hooghiemstra, 1988;Zhao et al, 2000;Mulitza et al, 2008;Itambi et al, 2009;Niedermeyer et al, 2009;Bouimetarhan et al, 2012Bouimetarhan et al, , 2013.…”

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinmentioning

confidence: 92%

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Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

et al. 2015

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Abstract. In tropical eastern Africa, vegetation distribution is largely controlled by regional hydrology, which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial for a better understanding of climate variability in the tropical southeastern African region. We present high-resolution pollen records from a marine sediment core recovered offshore of the Rufiji River delta. Our data document significant shifts in pollen assemblages during the last deglaciation, identifying, through changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics and sea-level changes) alterations. Specifically, arid conditions reflected by a maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1), suggesting that the expansion of drier upland vegetation was synchronous with cold Northern Hemisphere conditions. This arid period is followed by an interval in which forest and humid woodlands expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the shift to humid conditions around 14.8 kyr BP in the uplands are consistent with latitudinal shifts of the intertropical convergence zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of well-developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as to the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ∼ 14.8 kyr BP, suggesting an increased moisture availability and river runoff in the coastal area. The results of this study highlight the decoupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

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Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinsupporting

confidence: 87%

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinsupporting

confidence: 80%

Section: Paleoclimate and Controlling Mechanisms In The Uplands Durinmentioning

confidence: 92%

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Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

et al. 2015

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“…The length of the dry season has often been emphasized as a major control of vegetation structure and patterns in the tropics (Thomas, 1973;Box and Fujiwara , 2005;Vincens et al, 2007;Ngomanda et al, 2009). However, the relation between vegetation composition and climate is often described in a simple way using annual descriptors such as temperature and precipitation ).…”

Section: Introductionmentioning

confidence: 99%

Simulated effects of a seasonal precipitation change on the vegetation in tropical Africa

et al. 2010

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Abstract. Pollen data collected in Africa at high (Kuruyange, valley swamp, Burundi) and low altitude (Victoria, lake, Uganda; Ngamakala, pond, Congo) showed that after 6 ky before present (BP), pollen of deciduous trees increase their relative percentage, suggesting thus the reduction of the annual amount of precipitation and/or an increase of in the length of the dry season. Until now, pollen-climate transfer functions only investigated mean annual precipitation, due to the absence of modern pollen-assemblage analogs under diversified precipitation regimes. Hence these functions omit the potential effect of a change in precipitation seasonality modifying thus the length of the dry season. In the present study, we use an equilibrium biosphere model (i.e. BIOME3.5) to estimate the sensitivity of equatorial African vegetation, at specific sites, to such changes. Climatic scenarios, differing only in the monthly distribution of the current annual amount of precipitation, are examined at the above three locations in equatorial Africa. Soil characteristics, monthly temperatures and cloudiness are kept constant at their present-day values. Good agreement is shown between model simulations and current biomes assemblages, as inferred from pollen data. To date, the increase of the deciduous forest component in the palaeodata around 6 ky BP has been interpreted as the beginning of a drier climate period. However, our results demonstrate that a change in the seasonal distribution of precipitation could also induce the observed changes in vegetation types. This study confirms the importance of taking into account seasonal changes in the hydrological balance. Palaeoecologists can greatly benefit from the use of dynamic process based vegetation modCorrespondence to: E. S. Gritti (emmanuel.gritti@cefe.cnrs.fr) els to acccount for modification of the length of the dry season when they wish to reconstruct vegetation composition or to infer quantitative climate parameters, such as temperature and precipitation, from pollen or vegetation proxy.

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“…Our knowledge mainly comes from studies on east African lakes, which focus on the climate of East Africa and the Rift Mountains (e.g. Vincens et al, 2005Vincens et al, , 2007Bonnefille and Chalié, 2000;Johnson et al, 2004). They are, therefore, less suitable to monitor the effects of ITCZ and CAB variability on climate and vegetation of west southern Africa.…”

Section: Introductionmentioning

confidence: 99%

Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)

Dupont

Behling²,

Kim

2008

Clim. Past

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Abstract. ODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant.

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Influence of rainfall seasonality on African lowland vegetation during the Late Quaternary: pollen evidence from Lake Masoko, Tanzania

Abstract: Except in areas where human impact is pronounced, the modern distribution and high diversity of vegetation types in tropical Africa are mainly constrained by climate. During the Late Quaternary, vegetation changes have been evidenced by pollen records from numerous East African sedimentary

Cited by 83 publications

References 68 publications

Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

Simulated effects of a seasonal precipitation change on the vegetation in tropical Africa

Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)

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