An environmental reconstruction of the last 10,000 14C years of a frequently flooded wetland ecos... more An environmental reconstruction of the last 10,000 14C years of a frequently flooded wetland ecosystem in the lower Magdalena valley in northern Colombia is presented, on the basis of a multi-disciplinary study of the sediments of the upper 15 m of the core from Boquillas (74°33'E, 9°7'N; 20 m a. s. l.). We used the following studies: pollen, lithology, organic structures, clay mineralogy, soil and sediment geochemistry, and δ13C values. The chronology is based on 13 AMS radiocarbon dates; the humic acid fractions were used in the case of seven samples. Pollen from local origin (swamps, open grass-rich vegetation, and gallery forest) show the development of the wetland area. River-transported pollen from a greater distance (dry forest, montane forest, Alnus) show changes in river activity and reflect large-scale changes of climatic conditions in the Momposina basin. From c. 10,010 to 9370 uncal B. P. (zone BQS-Ia) the river system was of high energy, as inferred by the lithological changes. The landscape was dominated by open grass-rich vegetation with gallery forest along the streams. A marked representation of Alnus and montane forest taxa indicate significant water transport and river dynamics. Climatic conditions were dry. From c. 9370-8430 uncal B. P. (zone BQS-Ib) wetlands were isolated from the main river system, and clayey sediments with kaolinite, smectite and illite as the main minerals accumulated in a lower-energy environment. Climatic conditions were dry and changes in the seasonal precipitation favoured the expansion of the gallery forest. From c. 8430 to 8040 uncal B. P. (zone BQS-Ic) low values of river-transported pollen indicate dry climatic conditions and open vegetation became more abundant. The flooding frequency of the Boquillas site diminished. From 8040 to 4900 uncal B. P. (zone BQS-Id) the Boquillas site was dominated by open vegetation with patches of gallery forest along the streams. Supply of river-transported allochthonous pollen (from many sources) was minimal. Clay minerals from the sediments suggest variable temperature and precipitation. From c. 4900 to 1550 uncal B. P. )zone BQS-II) the site was within the reach of the main river system as is the case today. Frequent flooding, coinciding with peaks of river-transported grains of Alnus and high sediment supply, point to high precipitation in the composite catchment area of the Magdalena, Cauca, San Jorge, and Cesár rivers. High values of phosphorous in the upper part of the core point to the presence of a pre-Hispanic civilization, approximately from 2000 uncal B. P. onward. Construction of an extensive drainage system allowed irrigation as well as drainage depending the annual cycle of precipitation. The landscape was significantly modified and allowed an extensive crop production on a system of raised fields.
Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico we... more Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico were studied to examine the past dynamics of the dry forest biome. Pollen, spores of coprophilous fungi, cyanobacteria and lithological changes are presented. The 390-cm Tixtla core (17830?N, 99824?W, 1400 m altitude) represents the last 2700 cal. yr; the 340-cm Huitziltepec core (17845?N, 99828?W, 1430 m altitude) represents the last 2050 cal. yr. Pollen shows climate-dependent competition between dry deciduous forest (with Asteraceae, Chamaesyce-type, Bursera, Euphorbia, Myrica and Lysiloma-Pithecellobium-type as main components) and moister (mesophyllous) forest (with Pinus, Quercus, Alnus and Juglans). Human impact on the environment is apparent during the entire record, as evidenced by crop cultivation (Zea mays, Amaranthus, Capsicum, Chenopodium), coprophilous fungi (Podospora-type and Sporormiella-type), deforestation (at Tixtla in particular) and lake eutrophication, ie, cyanobacteria blooms. Environmental change at both sites is summarized as follows. Period 1 (2700 Á/2450 cal. yr BP): abundant dry deciduous forest and climate conditions drier than today. Period 2 (2450 Á/1950 cal. yr BP): little change in proportions of dry deciduous and mesophyllous forest but floral composition of the forests differed between sites. Human occupation was low. Period 3 (1950 Á/1550 cal. yr BP): dry deciduous forest decreased while mesophyllous forest increased, indicating more humid climatic conditions. Populations expanded significantly around 1950 cal. yr BP. Period 4 (1550 Á/1070 cal. yr BP): maximum expansion of mesophyllous forest. Climate was more humid than today. Pre-Hispanic populations at Tixtla reached high numbers leading to deforestation and eutrophication. Period 5 (1070 Á/c. 750 cal. yr BP): shows abundant mesophyllous forest and lowest proportions of dry deciduous forest. Climate continued to be humid. There is evidence of forest harvesting, crop cultivation and dense human population. Period 6 (c. 750 Á/225 cal. yr BP): dry deciduous forest expanded and mesophyllous forest decreased. There was significant deforestation by pre-Hispanic people around Lake Tixtla. High population densities and frequent fires at both sites caused eutrophication of the lakes. Domesticated herbivores were introduced Â/AD 1500 and the presence of dung is reflected in the record of coprophilous fungi. Period 7 (the last 225 calendar years): the basins were used intensively by local people and their cattle. Dry deciduous forest continued to increase while mesophyllous forest decreased.
Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico we... more Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico were studied to examine the past dynamics of the dry forest biome. Pollen, spores of coprophilous fungi, cyanobacteria and lithological changes are presented. The 390-cm Tixtla core (17830?N, 99824?W, 1400 m altitude) represents the last 2700 cal. yr; the 340-cm Huitziltepec core (17845?N, 99828?W, 1430 m altitude) represents the last 2050 cal. yr. Pollen shows climate-dependent competition between dry deciduous forest (with Asteraceae, Chamaesyce-type, Bursera, Euphorbia, Myrica and Lysiloma-Pithecellobium-type as main components) and moister (mesophyllous) forest (with Pinus, Quercus, Alnus and Juglans). Human impact on the environment is apparent during the entire record, as evidenced by crop cultivation (Zea mays, Amaranthus, Capsicum, Chenopodium), coprophilous fungi (Podospora-type and Sporormiella-type), deforestation (at Tixtla in particular) and lake eutrophication, ie, cyanobacteria blooms. Environmental change at both sites is summarized as follows. Period 1 (2700 Á/2450 cal. yr BP): abundant dry deciduous forest and climate conditions drier than today. Period 2 (2450 Á/1950 cal. yr BP): little change in proportions of dry deciduous and mesophyllous forest but floral composition of the forests differed between sites. Human occupation was low. Period 3 (1950 Á/1550 cal. yr BP): dry deciduous forest decreased while mesophyllous forest increased, indicating more humid climatic conditions. Populations expanded significantly around 1950 cal. yr BP. Period 4 (1550 Á/1070 cal. yr BP): maximum expansion of mesophyllous forest. Climate was more humid than today. Pre-Hispanic populations at Tixtla reached high numbers leading to deforestation and eutrophication. Period 5 (1070 Á/c. 750 cal. yr BP): shows abundant mesophyllous forest and lowest proportions of dry deciduous forest. Climate continued to be humid. There is evidence of forest harvesting, crop cultivation and dense human population. Period 6 (c. 750 Á/225 cal. yr BP): dry deciduous forest expanded and mesophyllous forest decreased. There was significant deforestation by pre-Hispanic people around Lake Tixtla. High population densities and frequent fires at both sites caused eutrophication of the lakes. Domesticated herbivores were introduced Â/AD 1500 and the presence of dung is reflected in the record of coprophilous fungi. Period 7 (the last 225 calendar years): the basins were used intensively by local people and their cattle. Dry deciduous forest continued to increase while mesophyllous forest decreased.
The Basin of Ubaté-Chichinquirá (5°28′N, 73°45′ W, c. 2580 m altitude) includes the Fúquene Valle... more The Basin of Ubaté-Chichinquirá (5°28′N, 73°45′ W, c. 2580 m altitude) includes the Fúquene Valley and is located in the central part of the Eastern Cordillera of Colombia. Rocks and sediments were folded and faulted during the Miocene, uplifted during the (late) Pliocene, and affected by glaciers during the Pleistocene. Successive glacial and interglacial periods left significant marks in the landscape which were used to reconstruct six stages in the development of the landscape along a relative chronology. During early Pleistocene episode 1 glaciers formed U-shape valleys. Evidence of the impact of ice sheets has been found as far downslope as ca. 2900 m elevation. During episode 2 moraines developed which were cut by the present San José River. During episode 3 abundant sediment was produced by glacial erosion. It accentuated the sculpturing of hard rock and deepening of the drainage basin. The ancestral Ubaté-Suarez River constituted a dynamic erosive system that gave rise to deep V-shaped valleys and progressively formed a set of intricate valleys with a high sediment production. Finally, intense glacial and fluvio-glacial erosion led to a geomorphological system with high energy levels and intensive sediment transport leading to wide valleys. During episode 4 the Ubaté-Suarez River eroded and deepened its valley until it captured the old El Hato-San José Valley. It caused intense erosion of the moraine and the fluvio-glacial gravels. Deep V-shaped valleys stabilized in the high areas of the main drainage system and these valleys form the present-day fluvial sub-basins. During episode 5 the deep valley in the northern part of the Basin of Ubaté-Chichinquirá developed. During middle Pleistocene episode 6 colluvial sediments formed the Saboya dam and a lake was formed in the river valley of which the present Lake Fúquene is only a small remnant. Lithological changes indicate fluctuating water levels and Lake Fúquene must have expanded periodically up to an area 5 to 10 times the present-day surface.
A 7000-year pollen record of a 90 cm core from Chenevo (4°059 N, 70°219 W, 150 m alttitude) and a... more A 7000-year pollen record of a 90 cm core from Chenevo (4°059 N, 70°219 W, 150 m alttitude) and a 3500-year pollen record of a 285 cm core from Mozambique (3°589 N, 73°039 W, 175 m altitude) both from the savannas of the Llanos Orientales, Colombia, are presented. The records show dynamics between open savanna (Poaceae, Cyperaceae), woody savanna (Byrsonima, Curatella, Didymopanax), palm swamp (Mauritia, Mauritiella)
... Description of the pollen and charcoal records 5. Paleoenvironmental reconstruction and human... more ... Description of the pollen and charcoal records 5. Paleoenvironmental reconstruction and human ... In a biome-based interpretation of the Holocene development of disturbance vegetation ... of the first human populations in Colombia, and more widely in Latin America ([Becerra, 1994 ...
We present a synthesis of the palaeolimnological and palaeoclimatic reconstructions of four sites... more 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 Fú quene 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. D
Two sediment cores were recovered from two swamps in the dry forest lowland ecosystem of the Patí... more 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. 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).
Three pollen records are presented from the Pantano de Monica region (0º42 0 S, 72º04 0 W, 160 m ... more Three pollen records are presented from the Pantano de Monica region (0º42 0 S, 72º04 0 W, 160 m elevation) on the lower terrace of Rio Caquetá of the central Colombian Amazonas. Ten radiocarbon dates from three cores indicate that the deposits are of Holocene age, but the pollen data suggest that the record may also contain the Late Glacial. The core Pantano de Monica 1 covers the time interval from 11,150 BP (extrapolated) to 4730 BP. During the Late Glacial and early Holocene this swamp was smaller in size and waters were more shallow than today, with abundant Mauritia palm trees. This indicates that the lower terrace of the Caquetá River was better drained than today, which might be related to changes in the drainage system and=or drier conditions during that time. Late Glacial and early Holocene vegetational changes in the rain forests surrounding the swamp Pantano de Monica indicate successional stages, probably related to changes in the drainage system and=or climate changes. Presence of Podocarpus pollen grains up to 2.6% of the total sum (and influx of 78 grains cm 2 yr 1 ) point to the regional presence of Podocarpus at the beginning of the Holocene. Evidence of Podocarpus during glacial times in other pollen records from the Amazon basin has been taken as indicative of cooling. Core Pantano de Monica 2 was taken in a small swamp (1000 m distance to Pantano de Monica 1) and starts at 4000 BP when this location was well drained. Several changes in the composition of the rain forest are documented, such as increase in disturbance (increase of Cecropia) followed by a quick recovery (increase of Psychotria). Protium and Caryocar tree taxa were frequent, suggesting that the lower terrace area was well drained until 3080 BP, after which small swamps developed. Core Pantano de Monica 3 is from the wet forest in between the two swamps and represents the period since 3260 BP. Pollen data show a continuously increasing presence of palms, probably Euterpe, suggesting either a transition from well-drained to less drained conditions in the lower terrace during the late Holocene, and=or a more intensive human impact of the rain forest on the lower terraces of Rio Caquetá. The three records from the lower terrace of Rio Caquetá show different forest compositions in the past and indicate that the rain forest environments were not stable during Late Glacial and Holocene times. Comparison with other data from lowland records of northwestern South America suggest that climate change is a major factor for environmental change in central Colombian Amazon.
Biomes are reconstructed in Colombia from modern (core-top) pollen data derived from 22 sites alo... more Biomes are reconstructed in Colombia from modern (core-top) pollen data derived from 22 sites along an altitudinal gradient (2000±4100 m) that encompasses the tree line. The`biomization' methodology is described in a stepwise manner that details the reconstruction of vegetation along an altitudinal gradient. In the majority of the cases, the results are comparable to site-speci®c descriptions of the vegetation. At altitudes between 2000 and 3000 m, cool mixed forest and cool evergreen forest biomes are important. Between 3000 and 3700 m the cool grassland/shrub biome is dominant. Above 3700 m, the af®nity score to arboreal biomes is low with a concomitant increased af®nity to the cool grassland biome that co-dominates along with the cool grassland/shrub biome. Hence, the technique is shown successful at reconstructing modern vegetation, this is particularly so when af®nity scores to the range of biomes, rather the single most dominant biome, are used to describe vegetation composition. The results are able to delimit the altitudinally-induced changes in vegetation, from Andean forest associations, open forest and shrub grassland complex through to high altitude grasslands. However, this ability of the modern pollen data to predict the potential vegetation, via the biomization technique, is complicated by several site-speci®c factors that impact on the vegetation. Of particular importance are localised environmental conditions, particularly moisture regime. An additional area of interest is the impact that human activity has had on the vegetation. By manipulation of the input matrices, which are assigned a priori, and consultation of the range of biome af®nity scores, it is possible to identify which sites re¯ect an anthropogenic signal and how this is manifested within the pollen data. By investigating the range of af®nity scores, these factors can be identi®ed and the relatively subtle changes in reconstructed vegetation determined, in particular, how the composition and quantity of the arboreal component changes about the tree line. The results are discussed in the context of using tree line position, and altitudinally-induced¯oristic changes, for palaeoclimatic reconstruction. q
Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using p... more Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using pollen data assigned a priori to plant functional types and biomes. The chosen sites incorporate four savanna sites (Laguna Sardinas, Laguna Angel, El Piñal and Laguna Carimagua), a site on the transition between savanna and Amazon rainforest (Loma Linda) and a site within the Amazon rainforest (Pantano de Monica). The areal extent of tropical moist forest, tropical dry forest and steppe have been subject to significant change: differential responses of the vegetation to climatic shifts are related to changes in plant available moisture, duration of dry season and edaphic controls on the vegetation. The record from El Piñal shows that the present-day savanna vegetation, dominated by steppe (Poaceae) with little occurrence of woody savanna taxa (e.g. Curatella, Byrsonima), was present since the last glacial period of the northern hemisphere. Unfortunately, El Piñal is located on an edaphic savanna and is not particularly responsive to registering change. Most records cover the early Holocene; one site records the El Abra stadial (Younger Dryas equivalent), when forest expansion reflects more humid climatic conditions and higher plant available moisture. During the early and middle Holocene, the maximum expansion of steppe and tropical dry forest occurred, indicating that dry climatic conditions continued to around 4000 14 C BP. The following period, from shortly before 4000 14 C BP, is characterised by an increase in forest and gallery forests, reflecting a wetter period probably with a shorter annual dry season. Anthropogenic influence on the vegetation is recorded by all the records over the last millennial, particularly characterised by a reduction in forest cover and high amplitude changes in vegetation.
... Page 2. The Holocene 10,6 (2000) pp. 749756 Tropical rain-forest history from the Colombian ... more ... Page 2. The Holocene 10,6 (2000) pp. 749756 Tropical rain-forest history from the Colombian Pacific area: a 4200-year pollen record from Laguna Jotaordo´ JuanCarlos Berrıo, Hermann Behling* and Henry Hooghiemstra ...
This paper compares a new super-high resolution pollen record from a central location in Lake Fúq... more This paper compares a new super-high resolution pollen record from a central location in Lake Fúquene (4°N) with 3 pollen records from marginal sites from the same lake basin, located at 2540 m elevation in the Eastern Cordillera of Colombia. We harmonized the pollen sum of all records, and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records. We dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages, cyclostratigraphy, and orbital tuning using the new 284 ka long Fúquene Basin Composite record (Fq-BC) as the backbone ( Groot et al., 2011). We showed that a common ˜9 m cycle in the arboreal pollen percentage (AP%) records reflects obliquity forcing and drives vegetational and climatic change. The AP% records were tuned to the 41 kyr component filtered from standard benthic δ 18O LR04 record. Changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin. We calibrated the original 14C ages and used where necessary biostratigraphic correlation, i.e. for records shorter than one obliquity cycle. Pollen records from the periphery of the lake showed changes in the abundance of Alnus and Weinmannia forests more clearly while centrally located record Fq-9C shows a more integrated signal of regional vegetation change. The revised age models show that core Fq-2 reflects the last 44 ka and composite record Fq-7C the last 85.5 ka. Marginally located core Fq-3 has an age of 133 ka at 32 m core depth and the lowermost 11 m of sediments appear of older but unknown age. The longest record Fq-BC shows ˜60 yr resolution over the period of 284-27 ka. All pollen records are in support of a common regional vegetation development leading to a robust reconstruction of long series of submillennial climate oscillations reflecting Dansgaard-Oeschger (DO) cycles. Reconstructed climate variability in the tropical Andes since marine isotope stage (MIS) 8 compares well with NGRIP (δ 18O based), Epica Dome C (δD based) and the Mediterranean sea surface temperature record MD01-2443/44 (U K'37 based) underpinning the global significance of the climate record from this tropical Andean lake. A basin-wide biostratigraphy is presented and we concluded although with varying robustness that each core is representative of regional vegetational and climatic change.
The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent ... more 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.
A 450 cm long sediment core was collected from a swamp in the dry forest ecosystem of the Patía V... more A 450 cm long sediment core was collected from a swamp in the dry forest ecosystem of the Patía Valley in Colombia (02° 02′ N, 77° W at 750 m elevation). This core (Potrerillo-2) was analysed using pollen, lithostratigraphy and radiocarbon dates and was correlated with an ...
This paper compares a new super-high resolution pollen record from a central location in Lake Fúq... more This paper compares a new super-high resolution pollen record from a central location in Lake Fúquene (4 N) with 3 pollen records from marginal sites from the same lake basin, located at 2540 m elevation in the Eastern Cordillera of Colombia. We harmonized the pollen sum of all records, and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records. We dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages, cyclostratigraphy, and orbital tuning using the new 284 ka long Fúquene Basin Composite record (Fq-BC) as the backbone . We showed that a common w9 m cycle in the arboreal pollen percentage (AP%) records reflects obliquity forcing and drives vegetational and climatic change. The AP% records were tuned to the 41 kyr component filtered from standard benthic d 18 O LR04 record. Changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin. We calibrated the original 14 C ages and used where necessary biostratigraphic correlation, i.e. for records shorter than one obliquity cycle. Pollen records from the periphery of the lake showed changes in the abundance of Alnus and Weinmannia forests more clearly while centrally located record Fq-9C shows a more integrated signal of regional vegetation change.
Antes que todo es importante aclarar que la Institución Pública en Panamá que está facultada para... more Antes que todo es importante aclarar que la Institución Pública en Panamá que está facultada para fiscalizar a los Medios de Comunicación Social Panameños era la Dirección Nacional de Medios de Comunicación Social, que estuvo adscrita al Ministerio de Gobierno y Justicia (Ministerio del Interior) de la República de Panamá, y que a su vez tenia una Junta Nacional de Censura, tales facultades han sido delegadas actualmente a la Dirección Nacional de Comunicación del Ministerio de la Presidencia. A su vez existen otras facultades que son competencia de la Autoridad Nacional Reguladora de los Servicios Públicos (ASEP), tal como el otorgamiento de las frecuencias de Radio y Televisión, y además la misma Autoridad aprobó el Acuerdo de Autorregulación de los Medios de Comunicación Social en Panamá. Es además el Ministerio de Comercio e Industria quien está facultado para aprobar la licencia comercial de las Empresas de Prensa, Radio y Televisión.
An environmental reconstruction of the last 10,000 14C years of a frequently flooded wetland ecos... more An environmental reconstruction of the last 10,000 14C years of a frequently flooded wetland ecosystem in the lower Magdalena valley in northern Colombia is presented, on the basis of a multi-disciplinary study of the sediments of the upper 15 m of the core from Boquillas (74°33'E, 9°7'N; 20 m a. s. l.). We used the following studies: pollen, lithology, organic structures, clay mineralogy, soil and sediment geochemistry, and δ13C values. The chronology is based on 13 AMS radiocarbon dates; the humic acid fractions were used in the case of seven samples. Pollen from local origin (swamps, open grass-rich vegetation, and gallery forest) show the development of the wetland area. River-transported pollen from a greater distance (dry forest, montane forest, Alnus) show changes in river activity and reflect large-scale changes of climatic conditions in the Momposina basin. From c. 10,010 to 9370 uncal B. P. (zone BQS-Ia) the river system was of high energy, as inferred by the lithological changes. The landscape was dominated by open grass-rich vegetation with gallery forest along the streams. A marked representation of Alnus and montane forest taxa indicate significant water transport and river dynamics. Climatic conditions were dry. From c. 9370-8430 uncal B. P. (zone BQS-Ib) wetlands were isolated from the main river system, and clayey sediments with kaolinite, smectite and illite as the main minerals accumulated in a lower-energy environment. Climatic conditions were dry and changes in the seasonal precipitation favoured the expansion of the gallery forest. From c. 8430 to 8040 uncal B. P. (zone BQS-Ic) low values of river-transported pollen indicate dry climatic conditions and open vegetation became more abundant. The flooding frequency of the Boquillas site diminished. From 8040 to 4900 uncal B. P. (zone BQS-Id) the Boquillas site was dominated by open vegetation with patches of gallery forest along the streams. Supply of river-transported allochthonous pollen (from many sources) was minimal. Clay minerals from the sediments suggest variable temperature and precipitation. From c. 4900 to 1550 uncal B. P. )zone BQS-II) the site was within the reach of the main river system as is the case today. Frequent flooding, coinciding with peaks of river-transported grains of Alnus and high sediment supply, point to high precipitation in the composite catchment area of the Magdalena, Cauca, San Jorge, and Cesár rivers. High values of phosphorous in the upper part of the core point to the presence of a pre-Hispanic civilization, approximately from 2000 uncal B. P. onward. Construction of an extensive drainage system allowed irrigation as well as drainage depending the annual cycle of precipitation. The landscape was significantly modified and allowed an extensive crop production on a system of raised fields.
Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico we... more Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico were studied to examine the past dynamics of the dry forest biome. Pollen, spores of coprophilous fungi, cyanobacteria and lithological changes are presented. The 390-cm Tixtla core (17830?N, 99824?W, 1400 m altitude) represents the last 2700 cal. yr; the 340-cm Huitziltepec core (17845?N, 99828?W, 1430 m altitude) represents the last 2050 cal. yr. Pollen shows climate-dependent competition between dry deciduous forest (with Asteraceae, Chamaesyce-type, Bursera, Euphorbia, Myrica and Lysiloma-Pithecellobium-type as main components) and moister (mesophyllous) forest (with Pinus, Quercus, Alnus and Juglans). Human impact on the environment is apparent during the entire record, as evidenced by crop cultivation (Zea mays, Amaranthus, Capsicum, Chenopodium), coprophilous fungi (Podospora-type and Sporormiella-type), deforestation (at Tixtla in particular) and lake eutrophication, ie, cyanobacteria blooms. Environmental change at both sites is summarized as follows. Period 1 (2700 Á/2450 cal. yr BP): abundant dry deciduous forest and climate conditions drier than today. Period 2 (2450 Á/1950 cal. yr BP): little change in proportions of dry deciduous and mesophyllous forest but floral composition of the forests differed between sites. Human occupation was low. Period 3 (1950 Á/1550 cal. yr BP): dry deciduous forest decreased while mesophyllous forest increased, indicating more humid climatic conditions. Populations expanded significantly around 1950 cal. yr BP. Period 4 (1550 Á/1070 cal. yr BP): maximum expansion of mesophyllous forest. Climate was more humid than today. Pre-Hispanic populations at Tixtla reached high numbers leading to deforestation and eutrophication. Period 5 (1070 Á/c. 750 cal. yr BP): shows abundant mesophyllous forest and lowest proportions of dry deciduous forest. Climate continued to be humid. There is evidence of forest harvesting, crop cultivation and dense human population. Period 6 (c. 750 Á/225 cal. yr BP): dry deciduous forest expanded and mesophyllous forest decreased. There was significant deforestation by pre-Hispanic people around Lake Tixtla. High population densities and frequent fires at both sites caused eutrophication of the lakes. Domesticated herbivores were introduced Â/AD 1500 and the presence of dung is reflected in the record of coprophilous fungi. Period 7 (the last 225 calendar years): the basins were used intensively by local people and their cattle. Dry deciduous forest continued to increase while mesophyllous forest decreased.
Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico we... more Two lake sediment cores from Madre del Sur mountain range, Guerrero State, west-central Mexico were studied to examine the past dynamics of the dry forest biome. Pollen, spores of coprophilous fungi, cyanobacteria and lithological changes are presented. The 390-cm Tixtla core (17830?N, 99824?W, 1400 m altitude) represents the last 2700 cal. yr; the 340-cm Huitziltepec core (17845?N, 99828?W, 1430 m altitude) represents the last 2050 cal. yr. Pollen shows climate-dependent competition between dry deciduous forest (with Asteraceae, Chamaesyce-type, Bursera, Euphorbia, Myrica and Lysiloma-Pithecellobium-type as main components) and moister (mesophyllous) forest (with Pinus, Quercus, Alnus and Juglans). Human impact on the environment is apparent during the entire record, as evidenced by crop cultivation (Zea mays, Amaranthus, Capsicum, Chenopodium), coprophilous fungi (Podospora-type and Sporormiella-type), deforestation (at Tixtla in particular) and lake eutrophication, ie, cyanobacteria blooms. Environmental change at both sites is summarized as follows. Period 1 (2700 Á/2450 cal. yr BP): abundant dry deciduous forest and climate conditions drier than today. Period 2 (2450 Á/1950 cal. yr BP): little change in proportions of dry deciduous and mesophyllous forest but floral composition of the forests differed between sites. Human occupation was low. Period 3 (1950 Á/1550 cal. yr BP): dry deciduous forest decreased while mesophyllous forest increased, indicating more humid climatic conditions. Populations expanded significantly around 1950 cal. yr BP. Period 4 (1550 Á/1070 cal. yr BP): maximum expansion of mesophyllous forest. Climate was more humid than today. Pre-Hispanic populations at Tixtla reached high numbers leading to deforestation and eutrophication. Period 5 (1070 Á/c. 750 cal. yr BP): shows abundant mesophyllous forest and lowest proportions of dry deciduous forest. Climate continued to be humid. There is evidence of forest harvesting, crop cultivation and dense human population. Period 6 (c. 750 Á/225 cal. yr BP): dry deciduous forest expanded and mesophyllous forest decreased. There was significant deforestation by pre-Hispanic people around Lake Tixtla. High population densities and frequent fires at both sites caused eutrophication of the lakes. Domesticated herbivores were introduced Â/AD 1500 and the presence of dung is reflected in the record of coprophilous fungi. Period 7 (the last 225 calendar years): the basins were used intensively by local people and their cattle. Dry deciduous forest continued to increase while mesophyllous forest decreased.
The Basin of Ubaté-Chichinquirá (5°28′N, 73°45′ W, c. 2580 m altitude) includes the Fúquene Valle... more The Basin of Ubaté-Chichinquirá (5°28′N, 73°45′ W, c. 2580 m altitude) includes the Fúquene Valley and is located in the central part of the Eastern Cordillera of Colombia. Rocks and sediments were folded and faulted during the Miocene, uplifted during the (late) Pliocene, and affected by glaciers during the Pleistocene. Successive glacial and interglacial periods left significant marks in the landscape which were used to reconstruct six stages in the development of the landscape along a relative chronology. During early Pleistocene episode 1 glaciers formed U-shape valleys. Evidence of the impact of ice sheets has been found as far downslope as ca. 2900 m elevation. During episode 2 moraines developed which were cut by the present San José River. During episode 3 abundant sediment was produced by glacial erosion. It accentuated the sculpturing of hard rock and deepening of the drainage basin. The ancestral Ubaté-Suarez River constituted a dynamic erosive system that gave rise to deep V-shaped valleys and progressively formed a set of intricate valleys with a high sediment production. Finally, intense glacial and fluvio-glacial erosion led to a geomorphological system with high energy levels and intensive sediment transport leading to wide valleys. During episode 4 the Ubaté-Suarez River eroded and deepened its valley until it captured the old El Hato-San José Valley. It caused intense erosion of the moraine and the fluvio-glacial gravels. Deep V-shaped valleys stabilized in the high areas of the main drainage system and these valleys form the present-day fluvial sub-basins. During episode 5 the deep valley in the northern part of the Basin of Ubaté-Chichinquirá developed. During middle Pleistocene episode 6 colluvial sediments formed the Saboya dam and a lake was formed in the river valley of which the present Lake Fúquene is only a small remnant. Lithological changes indicate fluctuating water levels and Lake Fúquene must have expanded periodically up to an area 5 to 10 times the present-day surface.
A 7000-year pollen record of a 90 cm core from Chenevo (4°059 N, 70°219 W, 150 m alttitude) and a... more A 7000-year pollen record of a 90 cm core from Chenevo (4°059 N, 70°219 W, 150 m alttitude) and a 3500-year pollen record of a 285 cm core from Mozambique (3°589 N, 73°039 W, 175 m altitude) both from the savannas of the Llanos Orientales, Colombia, are presented. The records show dynamics between open savanna (Poaceae, Cyperaceae), woody savanna (Byrsonima, Curatella, Didymopanax), palm swamp (Mauritia, Mauritiella)
... Description of the pollen and charcoal records 5. Paleoenvironmental reconstruction and human... more ... Description of the pollen and charcoal records 5. Paleoenvironmental reconstruction and human ... In a biome-based interpretation of the Holocene development of disturbance vegetation ... of the first human populations in Colombia, and more widely in Latin America ([Becerra, 1994 ...
We present a synthesis of the palaeolimnological and palaeoclimatic reconstructions of four sites... more 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 Fú quene 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. D
Two sediment cores were recovered from two swamps in the dry forest lowland ecosystem of the Patí... more 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. 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).
Three pollen records are presented from the Pantano de Monica region (0º42 0 S, 72º04 0 W, 160 m ... more Three pollen records are presented from the Pantano de Monica region (0º42 0 S, 72º04 0 W, 160 m elevation) on the lower terrace of Rio Caquetá of the central Colombian Amazonas. Ten radiocarbon dates from three cores indicate that the deposits are of Holocene age, but the pollen data suggest that the record may also contain the Late Glacial. The core Pantano de Monica 1 covers the time interval from 11,150 BP (extrapolated) to 4730 BP. During the Late Glacial and early Holocene this swamp was smaller in size and waters were more shallow than today, with abundant Mauritia palm trees. This indicates that the lower terrace of the Caquetá River was better drained than today, which might be related to changes in the drainage system and=or drier conditions during that time. Late Glacial and early Holocene vegetational changes in the rain forests surrounding the swamp Pantano de Monica indicate successional stages, probably related to changes in the drainage system and=or climate changes. Presence of Podocarpus pollen grains up to 2.6% of the total sum (and influx of 78 grains cm 2 yr 1 ) point to the regional presence of Podocarpus at the beginning of the Holocene. Evidence of Podocarpus during glacial times in other pollen records from the Amazon basin has been taken as indicative of cooling. Core Pantano de Monica 2 was taken in a small swamp (1000 m distance to Pantano de Monica 1) and starts at 4000 BP when this location was well drained. Several changes in the composition of the rain forest are documented, such as increase in disturbance (increase of Cecropia) followed by a quick recovery (increase of Psychotria). Protium and Caryocar tree taxa were frequent, suggesting that the lower terrace area was well drained until 3080 BP, after which small swamps developed. Core Pantano de Monica 3 is from the wet forest in between the two swamps and represents the period since 3260 BP. Pollen data show a continuously increasing presence of palms, probably Euterpe, suggesting either a transition from well-drained to less drained conditions in the lower terrace during the late Holocene, and=or a more intensive human impact of the rain forest on the lower terraces of Rio Caquetá. The three records from the lower terrace of Rio Caquetá show different forest compositions in the past and indicate that the rain forest environments were not stable during Late Glacial and Holocene times. Comparison with other data from lowland records of northwestern South America suggest that climate change is a major factor for environmental change in central Colombian Amazon.
Biomes are reconstructed in Colombia from modern (core-top) pollen data derived from 22 sites alo... more Biomes are reconstructed in Colombia from modern (core-top) pollen data derived from 22 sites along an altitudinal gradient (2000±4100 m) that encompasses the tree line. The`biomization' methodology is described in a stepwise manner that details the reconstruction of vegetation along an altitudinal gradient. In the majority of the cases, the results are comparable to site-speci®c descriptions of the vegetation. At altitudes between 2000 and 3000 m, cool mixed forest and cool evergreen forest biomes are important. Between 3000 and 3700 m the cool grassland/shrub biome is dominant. Above 3700 m, the af®nity score to arboreal biomes is low with a concomitant increased af®nity to the cool grassland biome that co-dominates along with the cool grassland/shrub biome. Hence, the technique is shown successful at reconstructing modern vegetation, this is particularly so when af®nity scores to the range of biomes, rather the single most dominant biome, are used to describe vegetation composition. The results are able to delimit the altitudinally-induced changes in vegetation, from Andean forest associations, open forest and shrub grassland complex through to high altitude grasslands. However, this ability of the modern pollen data to predict the potential vegetation, via the biomization technique, is complicated by several site-speci®c factors that impact on the vegetation. Of particular importance are localised environmental conditions, particularly moisture regime. An additional area of interest is the impact that human activity has had on the vegetation. By manipulation of the input matrices, which are assigned a priori, and consultation of the range of biome af®nity scores, it is possible to identify which sites re¯ect an anthropogenic signal and how this is manifested within the pollen data. By investigating the range of af®nity scores, these factors can be identi®ed and the relatively subtle changes in reconstructed vegetation determined, in particular, how the composition and quantity of the arboreal component changes about the tree line. The results are discussed in the context of using tree line position, and altitudinally-induced¯oristic changes, for palaeoclimatic reconstruction. q
Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using p... more Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using pollen data assigned a priori to plant functional types and biomes. The chosen sites incorporate four savanna sites (Laguna Sardinas, Laguna Angel, El Piñal and Laguna Carimagua), a site on the transition between savanna and Amazon rainforest (Loma Linda) and a site within the Amazon rainforest (Pantano de Monica). The areal extent of tropical moist forest, tropical dry forest and steppe have been subject to significant change: differential responses of the vegetation to climatic shifts are related to changes in plant available moisture, duration of dry season and edaphic controls on the vegetation. The record from El Piñal shows that the present-day savanna vegetation, dominated by steppe (Poaceae) with little occurrence of woody savanna taxa (e.g. Curatella, Byrsonima), was present since the last glacial period of the northern hemisphere. Unfortunately, El Piñal is located on an edaphic savanna and is not particularly responsive to registering change. Most records cover the early Holocene; one site records the El Abra stadial (Younger Dryas equivalent), when forest expansion reflects more humid climatic conditions and higher plant available moisture. During the early and middle Holocene, the maximum expansion of steppe and tropical dry forest occurred, indicating that dry climatic conditions continued to around 4000 14 C BP. The following period, from shortly before 4000 14 C BP, is characterised by an increase in forest and gallery forests, reflecting a wetter period probably with a shorter annual dry season. Anthropogenic influence on the vegetation is recorded by all the records over the last millennial, particularly characterised by a reduction in forest cover and high amplitude changes in vegetation.
... Page 2. The Holocene 10,6 (2000) pp. 749756 Tropical rain-forest history from the Colombian ... more ... Page 2. The Holocene 10,6 (2000) pp. 749756 Tropical rain-forest history from the Colombian Pacific area: a 4200-year pollen record from Laguna Jotaordo´ JuanCarlos Berrıo, Hermann Behling* and Henry Hooghiemstra ...
This paper compares a new super-high resolution pollen record from a central location in Lake Fúq... more This paper compares a new super-high resolution pollen record from a central location in Lake Fúquene (4°N) with 3 pollen records from marginal sites from the same lake basin, located at 2540 m elevation in the Eastern Cordillera of Colombia. We harmonized the pollen sum of all records, and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records. We dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages, cyclostratigraphy, and orbital tuning using the new 284 ka long Fúquene Basin Composite record (Fq-BC) as the backbone ( Groot et al., 2011). We showed that a common ˜9 m cycle in the arboreal pollen percentage (AP%) records reflects obliquity forcing and drives vegetational and climatic change. The AP% records were tuned to the 41 kyr component filtered from standard benthic δ 18O LR04 record. Changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin. We calibrated the original 14C ages and used where necessary biostratigraphic correlation, i.e. for records shorter than one obliquity cycle. Pollen records from the periphery of the lake showed changes in the abundance of Alnus and Weinmannia forests more clearly while centrally located record Fq-9C shows a more integrated signal of regional vegetation change. The revised age models show that core Fq-2 reflects the last 44 ka and composite record Fq-7C the last 85.5 ka. Marginally located core Fq-3 has an age of 133 ka at 32 m core depth and the lowermost 11 m of sediments appear of older but unknown age. The longest record Fq-BC shows ˜60 yr resolution over the period of 284-27 ka. All pollen records are in support of a common regional vegetation development leading to a robust reconstruction of long series of submillennial climate oscillations reflecting Dansgaard-Oeschger (DO) cycles. Reconstructed climate variability in the tropical Andes since marine isotope stage (MIS) 8 compares well with NGRIP (δ 18O based), Epica Dome C (δD based) and the Mediterranean sea surface temperature record MD01-2443/44 (U K'37 based) underpinning the global significance of the climate record from this tropical Andean lake. A basin-wide biostratigraphy is presented and we concluded although with varying robustness that each core is representative of regional vegetational and climatic change.
The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent ... more 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.
A 450 cm long sediment core was collected from a swamp in the dry forest ecosystem of the Patía V... more A 450 cm long sediment core was collected from a swamp in the dry forest ecosystem of the Patía Valley in Colombia (02° 02′ N, 77° W at 750 m elevation). This core (Potrerillo-2) was analysed using pollen, lithostratigraphy and radiocarbon dates and was correlated with an ...
This paper compares a new super-high resolution pollen record from a central location in Lake Fúq... more This paper compares a new super-high resolution pollen record from a central location in Lake Fúquene (4 N) with 3 pollen records from marginal sites from the same lake basin, located at 2540 m elevation in the Eastern Cordillera of Colombia. We harmonized the pollen sum of all records, and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records. We dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages, cyclostratigraphy, and orbital tuning using the new 284 ka long Fúquene Basin Composite record (Fq-BC) as the backbone . We showed that a common w9 m cycle in the arboreal pollen percentage (AP%) records reflects obliquity forcing and drives vegetational and climatic change. The AP% records were tuned to the 41 kyr component filtered from standard benthic d 18 O LR04 record. Changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin. We calibrated the original 14 C ages and used where necessary biostratigraphic correlation, i.e. for records shorter than one obliquity cycle. Pollen records from the periphery of the lake showed changes in the abundance of Alnus and Weinmannia forests more clearly while centrally located record Fq-9C shows a more integrated signal of regional vegetation change.
Antes que todo es importante aclarar que la Institución Pública en Panamá que está facultada para... more Antes que todo es importante aclarar que la Institución Pública en Panamá que está facultada para fiscalizar a los Medios de Comunicación Social Panameños era la Dirección Nacional de Medios de Comunicación Social, que estuvo adscrita al Ministerio de Gobierno y Justicia (Ministerio del Interior) de la República de Panamá, y que a su vez tenia una Junta Nacional de Censura, tales facultades han sido delegadas actualmente a la Dirección Nacional de Comunicación del Ministerio de la Presidencia. A su vez existen otras facultades que son competencia de la Autoridad Nacional Reguladora de los Servicios Públicos (ASEP), tal como el otorgamiento de las frecuencias de Radio y Televisión, y además la misma Autoridad aprobó el Acuerdo de Autorregulación de los Medios de Comunicación Social en Panamá. Es además el Ministerio de Comercio e Industria quien está facultado para aprobar la licencia comercial de las Empresas de Prensa, Radio y Televisión.
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