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M. H. M. Groot,
R. G. Bogotá,
L. J. Lourens, H. Hooghiemstra,
M. Vriend,
J. C. Berrio,
E. Tuenter,
J. van der Plicht,
B. van Geel,
M. Ziegler, [......],
N. González,
J. H. F. Jansen,
M. Konert,
D. Ortega,
O. Rangel,
G. Sarmiento,
J. Vandenberghe,
T. van der Hammen,
M. van der Linden,
W. Westerhoff
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ABSTRACT: Tropical montane biome migration patterns in the northern Andes are
found to be coupled to glacial-induced mean annual temperature (MAT)
changes; however, the accuracy and resolution of current records are
insufficient to fully explore their magnitude and rates of change. Here
we present a ~60-year resolution pollen record over the past 284 000
years from Lake Fúquene (5° N) in Colombia. This record shows
rapid and extreme MAT changes at 2540 m elevation of up to 10 ± 2
°C within a few hundred of years that concur with the ~100 and
41-kyr (obliquity) paced glacial cycles and North Atlantic abrupt
climatic events as documented in ice cores and marine sediments. Using
transient climate modelling experiments we demonstrate that
insolation-controlled ice volume and greenhouse gasses are the major
forcing agents causing the orbital MAT changes, but that the model
simulations significantly underestimate changes in lapse rates and local
hydrology and vegetation feedbacks within the studied region due to its
low spatial resolution.
Climate of the Past Discussions 09/2010; 6:2117-2158.
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ABSTRACT: Two pollen records from La Chonta bog (2310 m altitude) and one pollen record of a soil profile (2430 m altitude) at a short distance from the bog permit the reconstruction of the vegetational history and climatic sequence of probably the last ca. 80 000 yr of the Cordillera de Talamanca, Costa Rica. The three pollen records can be correlated on the basis of three radiocarbon-dated horizons (> 39 900 yr BP, 34 850 yr BP and 1390 yr BP) and palynostratigraphy. Pollen concentration data provide indirect time control between radiocarbon-dated horizons of the La Chonta 2 core. During the Early Glacial successive fluctuations of the upper forest line occurred between ca. 2300 m and 2800 m altitude and the bog is alternately situated close to the subalpine rainforest belt and in the uppermontane rainforest belt. During the Pleniglacial (ca. 50 000-13 000 yr BP) the forest line fell to ca. 2000 m altitude and paramo vegetation surrounded the La Chonta site. During the Late Glacial the forest line shifted rapidly in ca. 270 yr to 2700–2800 m altitude and the lake became surrounded by Quercus-dominated upper montane rainforest during a period of ca. 1655 yr. A distinct climate cooling (by 2–2.5°C) followed during ca. 580 yr and the upper forest line dropped to ca. 2400 m altitude. This temperature rebound is probably equivalent to the Younger Dryas event. In the depression extensive Alnus carr and swamp vegetation developed. Finally, during the Holocene, the forest line shifted to 3300–3500 m elevation and the lower montane rainforest reached close to ca. 2300 m altitude. In the later part of the Holocene subparamo scrub with Hypericum, Puya, Compositae, Escallonia and Ericaceae largely replaced Alnus carr and the regional and local vegetation closely resembles the presentday composition. During the Last Glacial to Holocene transition a shift of the upper forest line of ca. 1400 m is inferred, corresponding to a glacial temperature depression at 2300 m altitude of ca. 8°C.
Journal of Quaternary Science 07/2006; 7(3):205 - 225. · 2.31 Impact Factor
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ABSTRACT: In this paper we present an environmental reconstruction for the north-eastern part of Colombia known as the Llanos Orientales (4°8′N, 70°23′W) based on diatom and sediment analyses of a core drilled in Lake El Piñtal and complementing published information from pollen analysis carried out for the same core. The diatom record obtained from the core was interpreted using modern diatom samples from El Piñal and surrounding lakes. The dominant diatom assemblage in the core is composed of several species of Aulacoseira including A. species 1 that could not be identified and could be a new species. The environmental reconstruction indicates that between 18,290 and 9020 l4C yr BP the lake was part of a river system where periods of fluvial sediment accumulation alternated with periods of erosion. The pollen record shows dry savanna conditions for this time, with a slight change towards wetter conditions after 10,690 14C yr BP. Between 9020 and? 1260 14C yr BP incipient lake conditions are indicated, but the presence of at least one hiatus indicates that the river was still present. It is possible that these conditions correspond to an incipient stage of an oxbow lake. The lake was shallow, with acidic water, low in nutrient concentration. Savanna herbs dominated the surroundings. Between c. 1260 and 1065 14C yr BP the lake finally became isolated from the river and conditions similar to those of today were established. Savanna is still the dominant vegetation. The last 1065 14C yr BP are missing from the record. The diatom analysis provided additional information to pollen-based reconstructions and gave a clearer picture of the hydrological evolution of the area, for instance, the decrease in Isoetes and increase in Cabomba was intepreted as indicating higher lake levels, whereas diatoms suggest quasi-lacustrine conditions caused by the isolation of the lake from the river and not an increase in water level. This has potential bearing on regional multi-site reconstructions.
Diatom Research 01/2005; 20(2):387-407. · 0.66 Impact Factor
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Robert Marchant,
Arnoud Boom,
Hermann Behling,
Henry Hooghiemstra,
Bert Melief,
Bas Van Geel,
Thomas Van,
Der Hammen,
Michael Wille,
R Marchant,
Behling A, H Hooghiemstra,
Van Geel,
Van Der Hammen,
T And Wille,
Colombian
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ABSTRACT: vegetation at the Last Glacial Maximum: a comparison of model-and pollen-based biome reconstructions. ABSTRACT: Colombian vegetation, at the ecological level of the biome, is reconstructed at the Last Glacial Maximum (LGM) using two methods. A reconstruction of modern biomes shows that, for the majority of the sites, the pollen data accurately reflect the potential vegetation, even though much of the original vegetation has been transformed by agricultural practices. At 18 000 14 C yr BP a generally cool and dry environment is reflected in biome assignments of cold mixed forests, cool evergreen forests and cool grassland/shrub, the latter extending to lower altitudes than presently recorded. Dif-ferential responses of the vegetation to climatic shifts are related to changes in moisture sources and the importance of edaphic control on the vegetation. Secondly, biomes at the LGM are also investi-gated by applying a vegetation model (BIOME-3) set to operate at CO 2 levels of 200 ppmV and with climatic data from 12 meteorological stations that encompass a range of environments within Colom-bia. At lower altitudes it is apparent that moisture is the dominant control on driving vegetation change whereas temperature becomes more important at higher altitudes. The combined reconstruc-tion of biome-scale vegetation dynamics in Colombia allows an understanding of the environmental controls on these to be developed that demonstrates the need to invoke different factors to explain the vegetation change rather than a uniform reduction in temperature or moisture.
Journal of Quaternary Science 01/2004; 19(19):721-732. · 2.31 Impact Factor
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ABSTRACT: The altitudinal vegetation distribution in the northern Andes during glacial time differed from the present-day conditions as a result of temperature and precipitation change. New evidence indicate that as a response to a reduced atmospheric partial CO(2) pressure (pCO(2)), the competitive balance between C(3) and C(4) plants have changed. Effects may have remained virtually undetected in pollen records, but can be observed using a stable carbon isotope analysis. Vegetation dominated by C(4) taxa, belonging to the families Cyperaceae (e.g. Bulbostylis and Cyperus) and Poaceae (e.g. Muhlenbergia, Paspalum and Sporobolus), may have been able to replace for a significant part the modern type C(3) taxa (e.g. species belonging to Carex, Rhynchospora, Aciachne, Agrostis, Calamagrostis, and Chusquea). Impact of reduced glacial atmospheric pCO(2) levels and lower glacial temperatures on the composition and the elevational distribution of the vegetation types is discussed. The present high Andean vegetation communities may differ from the glacial equivalents (non-modern analogue situation). We identified dry Sporobolus lasiophyllus tussock grassland and Arcytophyllum nitidum dwarfshrub paramo as the possible relict communities from glacial time. The effect on previous estimates of paleo-temperatures is estimated to be small.
Review of Palaeobotany and Palynology 07/2001; 115(3-4):147-160. · 1.64 Impact Factor
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M.B. Bush,
M. Stute,
M.-P. Ledru,
H. Behling,
P.A. Colinvaux,
P.E. De Oliveira,
E.C. Grimm, H. Hooghiemstra,
S. Haberle,
B.W. Leyden,
M.-L. Salgado-Labouriau,
R.. Webb
01/2001: pages 293-306;
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British Journal of Haematology - BRIT J HAEMATOL. 01/1997;
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ABSTRACT: During the Pleistocene the vegetation changes in the high Colombian Andes included changes from C3 to C4 plants. This is inferred from 13C values of the C31 n-alkane from the Funza-2 sedimentary record taken from the high plain of Bogotá at 2550 m elevation. The environmental factors thought to be responsible for these changes were investigated using a single point simulation of the BIOME3 vegetation model, including changes in precipitation, temperature and atmospheric CO2 concentrations. The model shows that changes are for a major part caused by these latter two factors. The isotopic signature of the n-alkanes of several extant C3 and C4 grasses from the area were determined to calibrate the interpretation of the isotopic record. From the geochemical record, we estimated the altitudinal distribution of C3 and C4 plants, using present grass distribution patterns based on floristic data as a template. This information, in combination with palaeotemperature estimates, enabled the reconstruction of atmospheric CO2 concentrations. The reconstructed CO2 concentrations follow the trends of the Vostok Antarctic ice core through three glacial and two interglacial stages. The lowest calculated CO2 concentration is ca. 210 ppmV for the glacial maxima and within the range of lowest values from Vostok, our highest value (310 ppmV) is for interglacial MIS 7. This represents a new method to reconstruct palaeoatmospheric pCO2. It is less accurate than measurements from ice cores, but has potential to be used for sediments that are much older than the ice cores.
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ABSTRACT: Two sediment cores were recovered from two swamps in the dry forest lowland ecosystem of the Patía Valley (Colombia). The 500-cm long core El Patía-1 was analysed using diatoms, pollen, lithostratigraphy, geochemistry, charcoal and radiocarbon dates. The 270-cm long core Patía-2 was analysed using pollen, lithostratigraphy and radiocarbon dates. The environmental reconstruction includes the local development and history of the Patía-1 swamp and the regional vegetation history of the two swamps. The environmental reconstruction shows a fluvial system in the area before 7830 14C yr BP (ca. 8590 cal yr BP). After this date, the river gradually moved away leading to the formation of the swamp Patía-1; open vegetation with patches of dry forest surrounded the swamp. Between 7670 and 6860 14C yr BP (8350–7690 cal yr BP), the swamp become partially isolated from the river and was a permanent water body which was alkaline and mesotrophic. During this period, the surroundings were covered by dry forest. From 6860 to 5870 14C yr BP (7690–6690 cal yr BP), the swamp was totally isolated from the river and suffered from frequent periods of desiccation and erosion. From 5870 to 3570 14C yr BP (6690–3890 cal yr BP), the swamp turned into a marsh/terrestrial environment and in the surrounding area, the dry forest alternated with open vegetation; it is possible that there were human impacts on the environment during this period. Between 3570 and 1990 14C yr BP (3890–2000 cal yr BP), unstable conditions prevailed. After 1990 14C yr BP (2000 cal yr BP), swamp conditions of permanent water were re-established; open vegetation surrounded the swamp. Agriculture and human activities were present and have continued since then. The climatic reconstruction suggests an increase in humidity at ca. 7670 14C yr BP (8350 cal yr BP) and a dry climate between 6860 and 5870 14C yr BP (7690–6690 cal yr BP).
Palaeogeography, Palaeoclimatology, Palaeoecology.
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[show abstract]
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ABSTRACT: Two sediment cores were recovered from two swamps in the dry forest lowland ecosystem of the Patía Valley (Colombia). The 500-cm long core El Patía-1 was analysed using diatoms, pollen, lithostratigraphy, geochemistry, charcoal and radiocarbon dates. The 270-cm long core Patía-2 was analysed using pollen, lithostratigraphy and radiocarbon dates. The environmental reconstruction includes the local development and history of the Patía-1 swamp and the regional vegetation history of the two swamps. The environmental reconstruction shows a fluvial system in the area before 7830 14 C yr BP (ca. 8590 cal yr BP). After this date, the river gradually moved away leading to the formation of the swamp Patía-1; open vegetation with patches of dry forest surrounded the swamp. Between 7670 and 6860 14 C yr BP (8350–7690 cal yr BP), the swamp become partially isolated from the river and was a permanent water body which was alkaline and mesotrophic. During this period, the surroundings were covered by dry forest. From 6860 to 5870 14 C yr BP (7690–6690 cal yr BP), the swamp was totally isolated from the river and suffered from frequent periods of desiccation and erosion. From 5870 to 3570 14 C yr BP (6690–3890 cal yr BP), the swamp turned into a marsh/terrestrial environment and in the surrounding area, the dry forest alternated with open vegetation; it is possible that there were human impacts on the environment during this period. Between 3570 and 1990 14 C yr BP (3890–2000 cal yr BP), unstable conditions prevailed. After 1990 14 C yr BP (2000 cal yr BP), swamp conditions of permanent water were re-established; open vegetation surrounded the swamp. Agriculture and human activities were present and have continued since then. The climatic reconstruction suggests an increase in humidity at ca. 7670 14 C yr BP (8350 cal yr BP) and a dry climate between 6860 and 5870 14 C yr BP (7690–6690 cal yr BP). D 2004 Elsevier B.V. All rights reserved.
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R. Marchant,
L. Almeida,
H. Behling,
J.C. Berrio,
M. Bush,
A. Cleef,
J. Duivenvoorden,
M. Kappelle,
P. De Oliveira,
A.T. de Oliveira-Filho,
S. Lozano-Garcia, H. Hooghiemstra,
M.P. Ledru,
B. Ludlow-Wiechers,
V. Markgraf,
V. Mancini,
M. Paez,
A. Prieto,
O. Rangel,
M.L. Salgado-Labouriau
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ABSTRACT: The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The ‘dictionary’ describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.
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ABSTRACT: We present a synthesis of the palaeolimnological and palaeoclimatic reconstructions of four sites in Colombia. The record from Lake El Caimito, the westernmost site on the Pacific Coast, dates from the Late Holocene and shows lacustrine sedimentation frequently interrupted by fluvial pulses. These pulses probably reflect periods of increased precipitation related to La Niña phases. East of El Caimito site is the Patía swamp, situated between the Western and Central Andean Cordilleras. The Patía records the dynamics of forest expansion/reduction and changes in water levels. Although the climatic signal of the Patia core is difficult to reconstruct, there is a clear increase in humidity in the Mid-Holocene. The Fúquene Lake record, on the Eastern Andean Cordillera, records dry and cold conditions during the Late Pleistocene, very humid conditions for the early Mid-Holocene, and dry conditions during the mid-Late Holocene. Las Margaritas site, on the eastern savannas, records dry conditions during the Early Holocene and overall humid conditions for the Mid- and Late Holocene. Climate conditions from the Fuquene and Las Margaritas sites seem to reflect the Holocene movements of the Intertropical Convergence Zone (ITCZ); the latter site being more affected by humidity coming from the Amazon region.
Palaeogeography, Palaeoclimatology, Palaeoecology.
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[show abstract]
[hide abstract]
ABSTRACT: During the Pleistocene the vegetation changes in the high Colombian Andes included changes from C3 to C4 plants. This is inferred from δ13C values of the C31n-alkane from the Funza-2 sedimentary record taken from the high plain of Bogotá at 2550 m elevation. The environmental factors thought to be responsible for these changes were investigated using a single point simulation of the BIOME3 vegetation model, including changes in precipitation, temperature and atmospheric CO2 concentrations. The model shows that changes are for a major part caused by these latter two factors. The isotopic signature of the n-alkanes of several extant C3 and C4 grasses from the area were determined to calibrate the interpretation of the isotopic record. From the geochemical record, we estimated the altitudinal distribution of C3 and C4 plants, using present grass distribution patterns based on floristic data as a template. This information, in combination with palaeotemperature estimates, enabled the reconstruction of atmospheric CO2 concentrations. The reconstructed CO2 concentrations follow the trends of the Vostok Antarctic ice core through three glacial and two interglacial stages. The lowest calculated CO2 concentration is ca. 210 ppmV for the glacial maxima and within the range of lowest values from Vostok, our highest value (310 ppmV) is for interglacial MIS 7. This represents a new method to reconstruct palaeoatmospheric pCO2. It is less accurate than measurements from ice cores, but has potential to be used for sediments that are much older than the ice cores.
Palaeogeography, Palaeoclimatology, Palaeoecology.
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ABSTRACT: The El Abra stadial is a climatic cooling event defined in the Eastern Cordillera of Colombia, which corresponds both in timing and intensity to the Younger Dryas climatic oscillation of the northern North Atlantic region. The stadial was preceded by the relatively warm Guantiva interstadial and followed by the warm Holocene. Colder climatic conditions during the El Abra stadial caused a 400 m lowering of the upper Andean forest limit below its altitudinal location during the preceding Guantiva interstadial. Translated in temperature change, this represents a drop in mean annual temperature of approximately 2 to 3°C. The lowering of the upper forest limit and inferred temperature change for the El Abra stadial, compared to Late Holocene conditions, are in the order of 600 m and 4°C, respectively. The transition of the Guantiva interstadial to the El Abra stadial has been radiocarbon dated at 11,210 ± 90 BP and 10,820 ± 60 BP. Climatic warming may have started shortly after 10,380 ± 90 BP, and near present-day temperatures were reached at least as early as 8920 ± 100 BP. Maximum cooling was probably attained between 10,800 BP and 10,300 BP. Further (AMS) radiocarbon dating is planned to establish more exactly the timing of the El Abra stadial. A glacial advance of El Abra age, the Bocatoma stade, has been recognized in the highest part of the Colombian Eastern Cordillera, the Sierra Nevada del Cocuy. During this advance, glaciers extended some 700 m lower than at present. A climatic cooling event of El Abra age, associated with shifts of the upper Andean forest limit and glacial advances, has also been recognized in other parts of Andean Colombia, including the Central Cordillera and the Sierra Nevada de Santa Marta.
Quaternary Science Reviews.
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ABSTRACT: Pollen, spore, macrofossil and stable isotope (C and N) analyses from a 266-cm sediment core collected from a swamp on the Eastern Arc Mountains, Tanzania, are used to reconstruct vegetation and environmental history. An estimated time scale based on five 14C ages records approximately 38,000 yr. This palaeorecord is the first from this biodiversity hotspot and importantly extends through the last glacial maximum (LGM). The altitudinal transition from montane to upper montane forest shifted from 1700–1800 m (38,000 14C yr BP) to 1800–1900 m (35,000–29,000 14C yr BP). From 29,000 to 10,000 14C yr BP, it shifted from 1850–1950 m across the LGM to 1750–1800 m (during 10,000–3500 14C yr BP), and to present-day elevations at 2000 m during the last 3500 14C yr BP. The relative ecosystem stability across the LGM may be explained by the Indian Ocean's influence in maintaining continuous moist forest cover during a period of East African regional climate aridity. During the late Holocene, presence of abundant coprophilous fungi and algal blooms demonstrates increasing human impact. Neurospora spores indicate frequent fires, coinciding with clear signals of decline in Podocarpus and Psychotria trees that possibly represent selective logging.
Quaternary Research.
