The use of quantitative mineralogy linked to palynological studies in palaeoenvironmental reconstruction : the case study of the "Lagoa Campestre" lake, Salitre, Minas Gerais, Brazil

La comparaison des contenus minéraux déterminés par spectroscopie IRTF et polliniques de sédiments lacustres de la région de Salitre (Brésil) montre que les variations des teneurs en phases minérales répercutent des changements régionaux ou locaux de l'environnement. Une évolution inverse entre couvert forestier et charge détritique des sédiments est observée pendant la phase lacustre pleistocène. La méthode utilisée permet la détection d'un hiatus sédimentaire marqué par un changement brutal du contenu minéral, ainsi que l'évaluation du caractère abrupt de certains changements du couvert végétal qui, en l'absence de datation, pourraient être confondus avec un hiatus sédimentaire. (Résumé d'auteur

Взаємозв'язок обводнення генеративних бруньок абрикоса й персика та температурних умов їх розвитку після виходу рослин зі стану спокою

Наведено результати досліджень динаміки обводнення генеративних бруньок абрикоса й персика в зимовий період та на початку вегетації, а також темпу накопичення деревами градусо-годин росту, необхідних для початку цвітіння. Встановлено взаємозв’язок між змінами температури повітря, які враховано при визначенні градусо-годин росту, та водним режимом генеративних бруньок.Представлены результаты исследований динамики обводненности генеративных почек абрикоса и персика в зимний период и в начале вегетации, а также темпа накопления деревьями градусо-часов роста, необходимых для начала цветения. Установлена взаимосвязь между изменениями температуры воздуха, которые учтены при определении градусо-часов роста, и водным режимом генеративных почек.The article presents the results of researching the watering dynamics of the apricot and peach generative buds in the period of their development in winter and in the beginning of the vegetation as well as accumulation tempo of the growing degree hours, which trees need to come into flowering. It was established the correlation between environmental temperature changes, taken into consideration while determining the growing degree hours, and water regime of generative buds

Holocene land-sea climatic links on the equatorial Pacific coast (Bay of Guayaquil, Ecuador)

Copyright © 2015 SAGE PublicationsWe analyzed the pollen content of a marine core located near the bay of Guayaquil in Ecuador to document the link between sea surface temperatures (SST) and changes in rainfall regimes on the adjacent continent during the Holocene. Based on the expansion/regression of five vegetation types, we observe three successive climatic patterns. In the first phase, between 11,700 and 7700 cal yr BP, the presence of a cloud (Andean) forest in the mid altitudes and mangroves in the estuary of the Guayas Basin, were associated with a maximum in boreal summer insolation, a northernmost position of the Intertropical Convergence Zone (ITCZ), a land- sea thermal contrast, and dryness. Between 7700 and 2850 cal yr BP, the expansion of the coastal herbs and the regression of the mangrove indicate a drier climate with weak ITCZ and low ENSO variability while austral winter insolation gradually increased. The interval between 4200 and 2850 cal yr BP was marked by the coolest and driest climatic conditions of the Holocene due to the weak influence of the ITCZ and a strengthening of the Humboldt Current. After 2850 cal yr BP, high variability and amplitude of the Andean forest changes occurred when ENSO frequency and amplitude increased, indicating high variability in land-sea connections. The ITCZ reached the latitude of Guayaquil only after 2500 cal yr BP inducing the bimodal precipitation regime we observe today. Our study shows that besides insolation, the ITCZ position and ENSO frequency, changes in eastern equatorial Pacific SSTs play a major role in determining the composition of the ecosystems and the hydrological cycle of the Ecuadorian Pacific coast and the Western Cordillera in Ecuador.Deutsche ForschungsgemeinschaftFrench Research Agenc

The last 50.000 years in the neotropics (Southern Brazil) : evolution of vegetation and climate

In the "Lagoa Campestre" (lake) of Salitre (19°S, 46°46'W, 970 m elev.), there are plant taxa belonging to many ecological groups that are encountered nowhere else at this latitude. Frequent incursions of polar advections causing cooling and humidity, a cool and foggy climate in the middle of the depression and warmer temperatures on the surrounding slopes help to maintain all these groups within a fairly restricted area. Late Pleistocene-Holocene climatic change has had a considerable impact on the flora and vegetation of Salitre. The pollen record of the 6 m deep core LC3 shows how cold forest trees such as #Araucaria angustifolia and #Drimys brasiliensis, semi-deciduous forest, halophytic plants and peat bog started to develop on this site. The initial period, between c. 50,000 and 40,000 yr B.P., was an arid phase not recorded in any other neotropical lowland site. It was followed by a period of high moisture levels (40,000 to 27,000 yr B.P.) with a maximum estimated at c. 35,000 yr B.P. The Late Glacial maximum is missing because of a gap in sedimentation. Humidity gradually increased during the Late Pleistocene, between 16,000 and 11,000 yr B.P. The early Holocene, 9500 to 5000 yr B.P., is characterized by a more marked seasonal pattern and higher temperatures, reaching a maximum c. 5000 yr B.P. The spread of semi-deciduous forest between 4000 and 3000 yr B.P. attests to a return of humidity. Comparison with the Serra Negra section (19°S, 46°45'-46'W, 1170 m elev.) not far from Salitre confirms the high moisture rates recorded at c. 35-40,000 yr B.P. (although temperatures were cooler at the altitude of Serra Negra, as is attested by the presence of #Araucaria$ forest) and also confirms the strong impact of polar advections on the climate of Southeastern Brazil. (Résumé d'auteur

The evolution of the continental and coastal environments during the last climatic cycle in Brazil (120 KY. B.P. to present)

Studies done in Brazil, under the CNPq (Brazil) and ORSTOM (France) agreement, allowed us to envisage the general trend of climatic changes that occurred during the last 60,000 years. At first, examination of successive accumulation and erosion phases, recorded within Central Brazilian valley deposits, provided evidence of importam changes in slope vegetation cover and in the hydraulic regime of water courses, and hence characteristics of precipitation and climate regimes. Studies of Tamanduá river valley deposits in the town of São Simão (State of São Paulo) showed that between 32 and 21 ky. B.P. the climate was humid, whereas between 17 and 11 ky. B.P. it was dry with very scarce and strong rains. From 10 ky to 8.5 ky. B.P. the climate was humid too. Finally, after 7.5 ky. B.P. the deposits revealed the existence of several dry episodes within a globally humid climate. Palynological and sedimentological analyses of lacustrine deposits sampled by vibrocorers in the Eastern Amazon (Carajás, State of Pará) and in Central Brazil (Salitre, State of Minas Gerais) permitted us to outline the evolutionary history of the vegetation cover within these regions during the last 60,000 years for Carajás and 30,000 years for Salitre and thus to have a preliminary idea about their past climates. Then, it was possible to show that at Carajás regression of the evergreen rainforest occurred four times, at about 60, 40, between 23-11 and 7-4 ky. B.P. Moreover, apparently the last rainforest regression episode was quite different from the previous three episodes. At Salitre, the most characteristic is the indication of the existence of Araucária forest between 12 and 8.5 ky. B.P. This Araucária forest location is clearly much further north than at present, which suggests that during that time the climate was wetter and colder. Finally, studies developed along the central Brazilian coast allowed us to show evidence of wind-/driven change in littoral dynamics during the last 5 ky. A detailed examination of Doce river (State of Espírito Santo) mouth beach-ridge geometry has shown inversions in littoral drift direction as a consequence of change in wave and then in wind regimes, reflecting characteristics of atmospheric circulation during the last 5 ky.Estudos feitos no Brasil, segundo um acordo entre o CNPq (Brasil) e ORSTOM (França), permitiram-nos vislumbrar a tendência geral de mudanças climáticas que ocorreram durante os últimos 60.000 anos. Primeiramente, o estudo de sucessivas fases de erosão e sedimentação, registradas nos depósitos de vale do Brasil Central, forneceram evidências de importantes mudanças na cobertura vegetal de vertentes e no regime hidráulico de cursos fluviais e então chegando-se às características dos regimes pluviométricos e climáticos. Estudos de depósitos do vale do rio Tamanduá na cidade de São Simão (SP) mostraram que entre 32 e 21 ka. A.P. o clima foi úmido, enquanto entre 17 e 11 ka. A.P. ele foi seco com chuvas esparsas e fortes. De 10 ka. a 8,5 ka. A.P. o clima foi também úmido. Finalmente, após 7,5 ka. A.P. os depósitos revelaram a existência de vários episódios secos através do clima globalmente úmido. Análises palinológicas e sedimentológicas de depósitos lacustres amostrados por vibrotestemunhador na Amazônia Oriental (Carajás, PA) e no Brasil Central (Salitre, MG) permitiram delinear a história evolutiva da cobertura vegetal nessas regiões, durante os últimos 60.000 anos para Carajás e 30.000 anos para Salitre, e então ter uma idéia preliminar sobre seus paleoclimas. Então foi possível mostrar que em Carajás por quatro vezes, há cerca de 60, 40, entre 23-11 e 7-4 Ka. A.P., ocorreu a regressão da floresta pluvial perene. Além disso, aparentemente o último episódio de regressão da floresta pluvial foi bem diferente dos três episódios anteriores. Em Salitre, mais característica é a indicação da existência de floresta de Araucária entre 12 e 8,5 Ka. A.P. A localização desta floresta de Araucária está claramente mais ao norte que atualmente, sugerindo que durante aquela época o clima era mais úmido e mais frio. Finalmente, estudos desenvolvidos na costa do Brasil Central mostraram evidências de mudanças na dinâmica costeira comandadas pelo vento durante os últimos 5 Ka. Um estudo detalhado da geometria das cristas praiais de desembocadura do rio Doce (ES) mostrou inversões no sentido da deriva litorânea como conseqüência de mudanças nos regimes da onda e do vento, permitindo conhecer as características da circulação atmosférica durante os últimos 5 Ka

Last Glacial Maximum in an Andean cloud forest environment (Eastern Cordillera, Bolivia): Comment and Reply

Whether the climate of tropical South America during the Last Glacial Maximum (LGM) was colder and drier or colder and wetter than present day has been widely debated. It is accepted, however, that the LGM in tropical South America was 2–9 °C colder than today (e.g., Betts and Ridgway, 1992; Bush et al., 2001). Without debating the merits of the following choices, if we assume a lapse rate in the LGM similar to the modern one of ~0.6 °C·100 m−1, then an intermediate cooling of 5 °C would lower the boundary between montane cloud forest and the overlying puna grasslands by ~800 or 900 m. Palynologists on both sides of the wet/dry debate have come to similar conclusions about forest-boundary lowering due to temperature decrease (reviewed by Flenley, 1998). In the Eastern Cordillera of Bolivia the modern puna–cloud forest boundary lies ~3400 m above sea level (masl). Ignoring any other environmental changes, LGM cooling would have lowered this boundary to 2500 or 2600 masl

Millenial-scale climatic and vegetation changes in a northern Cerrado (Northeast, Brazil) since the Last Glacial Maximum.

Abstract In the Southern Hemisphere, lacustrine sediments started to be deposited with the beginning of the deglaciation at ca 19,000 cal yr BP. At this time the region of Lake Cac -o was dominated by sparse and shrubby vegetation with dominance of steppic grasses in a poor sandy soil. The landscape did not present any ecological characteristics of a modern Cerrado. However single pollen grains of two Cerrado indicators, Byrsonima and Mimosa, suggest that some Cerrado species were able to survive under the prevailing arid climate, probably as small shrubs. After 15,500 cal yr BP, a sudden increase in the moisture rates is evidenced with the progressive expansion of rainforest showing successive dominance of various associations of taxa. The development of the forest stopped abruptly at the end of the Pleistocene between 12,800 and 11,000 cal yr BP, as attested by strong fires and the expansion of Poaceae. In the early Holocene an open landscape with a relatively high level of water in the lake preceded the progressive expansion of Cerrado species towards a denser forested landscape; fires are recorded from then on, resulting in the physiognomy of the Cerrado we know today. Late Pleistocene paleoenvironmental records from northern Brazil reflect the interplay between insolation forcing of two hemispheres with the local components represented by the interannual shift of the Inter Tropical Convergence Zone and the influence of seasonal equatorwards polar air incursions.

Updated site compilation of the Latin American Pollen Database

Flantua, Suzette G A et al.The updated inventory of the Latin American Pollen Database (LAPD) offers a wide range of new insights. This paper presents a systematic compilation of palynological research in Latin America. A comprehensive inventory of publications in peer-reviewed and grey literature shows a major expansion of studies over the last decades. The inventory includes 1379 cores and sections with paleoecological data and more than 4800 modern samples from throughout the continent. Through the years, pollen datasets extend over increasing spans of time and show improved taxonomic and temporal resolution. Currently, these datasets are from 12 modern biomes and 30 countries, covering an altitudinal range of 0 to 6300. m asl. The most densely sampled regions are the Colombian Andes, the southeast coast of Brazil, and Patagonia. Underrepresented biomes are the warm temperate mixed forest (3%), dry forests (3%), and warm temperate rainforest (1%); whereas steppe, tropical rainforest, and cool grass shrublands, such as the páramos, are generally well represented (all >. 17%). There are 126 records that span the late Pleistocene to the Last Glacial Maximum transition (21,000. cal. yr BP), and >. 20% of the records cover the Younger Dryas interval and the Pleistocene/Holocene transition. Reanalysis of numerous sites using multiproxy tools emphasize the informative value of this approach in paleoenvironmental reconstruction. We make suggestions for several pollen sites and regions to be visited again; similarly we identify some key research questions that have yet to be answered. The updated LAPD now provides the platform to support an exciting new phase of global palynological research in which multi-site data are being integrated to address current cutting-edge research questions. The LAPD compilation of sites and the literature database will be available through the Neotoma Paleoecology Database website and a new LAPD website by the end of 2015We thank the Netherlands Organization for Scientific Research (NWO, grant 2012/13248/ALW) for financial support of this project.Peer reviewe