Studien zur Vegetations-, Feuer- und Klimadynamik im Spätquartär als Beitrag zum Schutz und Management des Biodiversitätszentrums Mata Atlantica in Südbrasilien

Im südbrasilianischen Hochland kommt heute eine faszinierende Landschaft aus Mosaiken von Wald und Grasland (Campos) vor. Die verschiedenen Vegetationsökosysteme wie Campos, Araukarienwald und Atlantischer Regenwald gehören zum Atlantischen Regenwaldbiom, welches die am stärksten zerstörte Vegetation Brasiliens darstellt. Studien zu Paläoumwelt und Paläoklima liefern wichtige Informationen zum Verständnis der Entwicklung, Stabilität und Dynamik dieser artenreichen Ökosysteme für heute und in Zukunft. Durch Pollenanalyse können Veränderungen von Vegetation und Klima in der Vergangenheit rekonstruiert werden. Palynologische Studien liefern wichtige Grundlagen zur Paläoumweltgeschichte, welche für die Erstellung von Erhaltungs- und Managementstrategien unerlässlich sind. Anhand von drei Pollen- und Holzkohlearchiven wurden die Paläoumweltveränderungen des subtropischen südbrasilianischen Hochlandes für das Spätquartär interpretiert. Zwei Sedimentarchive von der Serra Geral im Staat Rio Grande do Sul und eines von der Serra do Tabuleiro im Staat Santa Catarina wurden mittels Pollen- und Holzkohleanalyse sowie multivariater Analyse untersucht. Die paläoökologischen Ergebnisse für das subtropische südbrasilianische Hochland zeigen enge Verbindungen zwischen Vegetationszusammensetzung, Vegetationsdynamik und dem zukünftigen globalen Klimawandel

Araucaria forest dynamics in relation to fire frequency in southern Brazil based on fossil and modern pollen dataf

To elucidate the relationship between forest dynamics and fire frequency pollen percentages and charcoal amounts from a 120 cm long peat core and from samples of modern pollen rain were collected along a transect. The study site in southern Brazil is characterized by a species-rich mosaic of grassland-Araucaria forest. It is of crucial importance for management strategies for conservation to understand the development and maintenance of these vegetation mosaics including their sharp forest-grassland boundaries. During the late Holocene, considerable changes occurred in the area. From Anno Domini (AD) 1360 to 1410, the area was dominated by Campos (grassland) vegetation and fire was very common. From AD 1410 to 1500, Araucaria forest expanded and fire was less frequent. From AD 1500 to 1580, Campos grassland spread and the Araucaria forest ceased its development, apparently due to the increase of fire. From AD 1580 to 1935, after a decrease in fire frequency, Araucaria forest expanded again. From AD 1935 to the present, the Araucaria forest expanded while the Campos area decreased. Fire was very rare in this period. The results indicate a strong interaction of forest expansion, forming a mosaic of Campos and Araucaria forest, and the frequency of fire during the past 600 years. A possible collapse of the indigenous population following the post-Colombian colonization in southern Brazil after about AD 1550 may have caused a great reduction of fire frequency. The introduction of cattle (probably after AD 1780) and the resulting decrease of fire frequency might be the reason for forest expansion. Fire is probably the most important factor controlling the dynamics of the forest-grassland mosaics and the formation of sharp borders between these two vegetation types. (C) 2010 Elsevier B.V. All rights reserved.Deutsche Forschungsgemeinschaft (DFG)Deutsche Forschungsgemeinschaf (DFG)Inter American Institut for Global Change Research (IAI)Inter American Institut for Global Change Research (IAI

Upper Pleistocene to Holocene peatland evolution in Southern Brazilian highlands as depicted by radar stratigraphy, sedimentology and palynology

Paleoenvironmental interpretation of proxy data derived from peatlands is largely based upon an evolutionary model for ombrotrophic bogs, in which peat accumulates in still environments. Reports on proxies obtained from minerotrophic fens, where hydrologic inputs are variable, are less common. In this study, a highland peatland in southern Brazil is presented through ground penetrating radar (GPR) and sedimentological, palynological and geochronologic data. The radar stratigraphic interpretation suggests a relatively complex history of erosion and deposition at the site since the beginning of Marine Isotope Stage 3 (MIS 3) interstadial period. In spite of this, radar stratigraphic and palynologic interpretations converge. Electromagnetic reflections tend to group in clusters that show lateral coherence and correlate with different sediment types, while pollen grains abound and are well preserved. As a result, the study of minerotrophic fens provides a source of proxies. suggesting that ombrotrophic bogs are not the only reliable source of data in wetlands for palynological analysis. (C) 2012 University of Washington. Published by Elsevier Inc. All rights reserved.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)CNPq - Conselho Nacional de Desenvolvimento Cientifico e Tecnologico [152377/2007-7]Fundacao de Apoio a Pesquisa Cientifica e Tecnologica do Estado de Santa Catarina (FAPESC)FAPESC - Fundacao de Apoio a Pesquisa Cientifica e Tecnologica do Estado de Santa Catarina [CON08857/2007-9

When archives are missing, deciphering the effects of public policies and climate variability on the Brazilian semi-arid region using sediment core studies

International audienceThe northeastern region of Brazil is the most densily populated and biodiverse semi-arid regions of the planet. Effects of the natural climate variability and colonization on the landscape have been described since the beginning of the 16 th century but little is known about their effects on natural resources. Climate projections predict temperatures above 40 °C and an increase in the number and duration of droughts at the end of the 21 st century with strong societal impacts. Here, we analyze the influence of public policies, human activities and natural climate variability on the environment over the last 60 years. Our study is based on sedimentological and environmental reconstructions from two sediment cores collected in two dam lakes on the river Acaraú in the State of Ceará. Multiproxy analyses of both cores (inorganic geochemistry, pollen, charcoal, remote sensing) at an annual resolution showed that 1) at interannual scale composition and distribution of the dry forest (known as Caatinga) were not affected by the alternance of drought and high moisture episodes; 2) at decadal scale human activities such as agriculture were reflected by changes in vegetation cover and fishery by progressive changes in lake trophic status; 3) public policies were able to promote changes in the landscape e.g., land colonization with the regression of the dry forest and irrigation plan able to amplify the deforestation and change the floristic composition. Thanks to paleoscience approach, our environmental diagnosis should help future decision-making and provide guidelines for preservation of resources and wellbeing of the inhabitants