105,706 research outputs found
POLLEN RECORDS, POSTGLACIAL | South America
No full textThe postglacial pollen records from South America indicate that different ecosystems were not stable during the Holocene. The variation in Atlantic sea level was probably the major factor in paleoenvironmental changes for the low-lying Amazon Basin region. Large areas of seasonally inundated Várzea and Igapó forests developed after about 3,000 yr. Relatively high water stands might also be due to greater annual rainfall in western, central, and eastern Amazonia, which is also indicated by the marked expansion of Amazon rainforest, both north and south of the equator since the mid-Holocene, but especially during the late Holocene period. This climate change contrasts with that of the Caatinga region in northeastern Brazil. Evidence of significant vegetational and climate change is also found in southeastern Brazil by the marked expansion of semideciduous forest and Atlantic rainforest reducing the Cerrado area during mid- and late Holocene and in southern Brazil by the expansion of Araucaria forests, reducing the area of Campos during the late Holocene, specially during the last 1 kyr. The amount of annual precipitation must have been higher and the length of the annual dry season must have been shorter than during early and mid-Holocene times. The strongest human impact is evident from pollen records specially for the late Holocene period
Holocene vegetation and environmental changes of peat ecosystems in southwestern and northeastern Amazonia
No full texthttp://dx.doi.org/10.13039/501100004543 China Scholarship Counci
Structural characterization of Methanobactin using Nuclear Magnetic Resonance (NMR)
No full textColor poster with text and diagrams describing research conducted by Lee Behling under the supervision of Warren Gallagher and Scott Hartsel.Methanobactin ia a small copper-sequestering molecule produced by the bacteria Methylosinus trichosporium OB3b. This research employed nuclear magnetic resonance (NMR) and mass spectroscopy to elucidate the structure of methanobactin when exposed to low levels of copper.University of Wisconsin--Eau Claire Office of Research and Sponsored Programs
Pollen-based temperature and precipitation inferences for the montane forest of Mt. Kilimanjaro during the last Glacial and the Holocene
No full textThe relationship between modern pollen-rain taxa and measured climate variables was explored along the elevational gradient of the southern slope of Mt. Kilimanjaro, Tanzania. Pollen assemblages in 28 pollen traps positioned on 14 montane forest vegetation plots were identified and their relationship with climate variables was examined using multivariate statistical methods. Canonical correspondence analysis revealed that the mean annual temperature, mean annual precipitation and minimum temperature each account for significant fractions of the variation in pollen taxa. A training set of 107 modern pollen taxa was used to derive temperature and precipitation transfer functions based on pollen subsets using weighted-averaging-partial-least-squares (WA-PLS) techniques. The transfer functions were then applied to a fossil pollen record from the montane forest of Mt. Kilimanjaro and the climate parameter estimates for the Late Glacial and the Holocene on Mt. Kilimanjaro were inferred. Our results present the first quantitatively reconstructed temperature and precipitation estimates for Mt Kilimanjaro and give highly interesting insights into the past 45 000 yr of climate dynamics in tropical East Africa. The climate reconstructions are consistent with the interpretation of pollen data in terms of vegetation and climate history of afro-montane forest in East Africa. Minimum temperatures above the frostline as well as increased precipitation turn out to be crucial for the development and expansion of montane forest during the Holocene. In contrast, consistently low minimum temperatures as well as about 25% drier climate conditions prevailed during the pre LGM, which kept the montane vegetation composition in a stable state. In prospective studies, the quantitative climate reconstruction will be improved by additional modern pollen rain data, especially from lower elevations with submontane dry forests and colline savanna vegetation in order to extend the reference climate gradient
Corrigendum to "Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)" published in Clim. Past, 4, 107–124, 2008
No full textNo abstract available
Carnivorous leaves from Baltic amber
No full textSadowski E-M, Seyfullah LJ, Friederike S, Fleischmann A, Behling H, Schmidt AR. Carnivorous leaves from Baltic amber. Proceedings of the National Academy of Sciences. 2015;112(1):190-195.The fossil record of carnivorous plants is very scarce and macro-fossil evidence has been restricted to seeds of the extant aquatic genus Aldrovanda of the Droseraceae family. No case of carnivorous plant traps has so far been reported from the fossil record. Here, we present two angiosperm leaves enclosed in a piece of Eocene Baltic amber that share relevant morphological features with extant Roridulaceae, a carnivorous plant family that is today endemic to the Cape flora of South Africa. Modern Roridula species are unique among carnivorous plants as they digest prey in a complex mutualistic association in which the prey-derived nutrient uptake depends on heteropteran insects. As in extant Roridula, the fossil leaves possess two types of plant trichomes, including unicellular hairs and five size classes of multicellular stalked glands (or tentacles) with an apical pore. The apices of the narrow and perfectly tapered fossil leaves end in a single tentacle, as in both modern Roridula species. The glandular hairs of the fossils are restricted to the leaf margins and to the abaxial lamina, as in extant Roridula gorgonias. Our discovery supports current molecular age estimates for Roridulaceae and suggests a wide Eocene distribution of roridulid plants
Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)
No full textODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant
Holocene vegetation dynamics, carbon deposition, sea level changes, and human impact inferred from the Lagoa da Fazenda core in the Baía de Caxiuanã region, Northern Brazil
No full texthttp://dx.doi.org/10.13039/501100003593 Conselho Nacional de Desenvolvimento Cientifico e Tecnologicohttp://dx.doi.org/10.13039/501100004543 China Scholarship Counci
Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)
No full textODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant
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