API src

Found 53 results.

Other language confidence: 0.8629778350334771

Pollen and environmental reconstruction, Holocene dynamics of tropical rainforest, climate, fire, human impact and land use in Sulawesi and Sumatra, Indonesia

The present-day configuration of Indonesia and SE Asia is the results of a long history of tectonic movements, volcanisms and global eustatic sea-level changes. Not indifferent to these dynamics, fauna and flora have been evolving and dispersing following a complicate pattern of continent-sea changes to form what are today defined as Sundaland and Wallacea biogeographical regions. The modern intraannual climate of Indonesia is generally described as tropical, seasonally wet with seasonal reversals of prevailing low-level winds (Asian-Australian monsoon). However at the interannual scale a range of influences operating over varying time scales affect the local climate in respect of temporal and spatial distribution of rainfall. Vegetation generally reflects climate and to simplify it is possible to distinguish three main ecological elements in the flora of Malaysia: everwet tropical, seasonally dry tropical (monsoon) and montane. Within those major ecological groups, a wide range of specific local conditions caused a complex biogeography which has and still attract the attention of botanists and biogeographers worldwide. Being one of the richest regions in the Worlds in terms of species endemism and biodiversity, Indonesia has recently gone through intensive transformation of previously rural/natural lands for intensive agriculture (oil palm, rubber, cocoa plantations and rice fields). Climate change represents an additional stress. Projected climate changes in the region include strengthening of monsoon circulation and increase in the frequency and magnitude of extreme rainfall and drought events. The ecological consequences of these scenarios are hard to predict. Within the context of sustainable management of conservation areas and agro-landscapes, Holocene palaeoecological and palynological studies provide a valuable contribution by showing how the natural vegetation present at the location has changed as a consequence of climate variability in the long-term (e.g. the Mid-Holocene moisture maximum, the modern ENSO onset, Little Ice Age etc.). The final aim of my PhD research is to compare the Holocene history of Jambi province and Central Sulawesi. In particular: - Reconstructing past vegetation, plant diversity and climate dynamics in the two study areas Jambi (Sumatra) and Lore Lindu National Park (Sulawesi) - Comparing the ecological responses of lowland monsoon swampy rainforest (Sumatra) and everwet montane rainforests (Sulawesi) to environmental variability (vulnerability/resilience) - Investigating the history of human impact on the landscape (shifting cultivation, slash and burn, crop cultivation, rubber and palm oil plantation) - Assessing the impact and role of droughts (El Niño) and fires - Adding a historical perspective to the evaluation of current and future changes.

Holozaenzeitliche Rheinstromverlagerungen zwischen Duesseldorf und der Landesgrenze

Darstellung holozaenzeitlicher Rheinverlaeufe anhand ausgewaehlter Zeitscheiben. Es sollen klimatische und menschliche Einfluesse auf das Abflussverhalten des Rheins untersucht werden. Interdisziplinaere Zusammenarbeit mit Archaeologen und Historikern.

Beach sand deposits on the coast of southern Norway as a natural experimental setup to test hypotheses on soil development and luminescence dating

Beach sand deposits are widespread in the area around Sandefjord, at the western coast of the Oslofjord, southern Norway. The age of the deposits continuously increases with elevation, as the area has been subject to steady glacio-isostatic uplift throughout the Holocene. Existing local sea level curves provide age control related to elevation. Thus, the area offers excellent conditions to test hypotheses on soil formation and OSL dating. A chronosequence covering the last 10 000 years will be established. A preliminary study showed that soil formation leads to Podzols within 4300 - 6600 years. Micromorphological analyses suggest that clay illuviation takes place before and below podzolisation. It is hypothesised that clay translocation goes on contemporarily with podzolisation, but at greater soil depth, where the chemical conditions are suitable. This hypothesis will be proved by more detailed micromorphological investigation and chemical analyses. The factors controlling soil forming processes and their rates, will be determined by analyzing elemental composition, primary minerals and clay mineralogy. Preliminary OSL dating tests suggest that the beach sand deposits are OSL dateable despite the high latitude. This hypothesis will be checked by comparing OSL datings to ages derived from the 14C-based sea level curves.

Late-Glacial and Holocene vegetational stability of southern South America

This project focuses on the long-term stability (or otherwise) of vegetation, based on a series of multi-proxy records in southern South America. We will build a network of sites suitable for high-resolution reconstructions of changes in vegetation since the Last Glacial Maximum, and use these to test a null hypothesis that changes in vegetation over the past 14,000 years are driven by internal dynamics rather than external forcing factors. The extent to which the null hypothesis can be falsified will reveal the degree to which we can expect to be able to predict how vegetation is affected by external events, including future climate change. The southern fringes of the South American landmass provide a rare opportunity to examine the development of moorland vegetation with sparse tree cover in a wet, cool temperate climate of the Southern Hemisphere. We present a record of changes in vegetation over the past 17,000 years, from a lake in extreme southern Chile (Isla Santa Inés, Magallanes region, 53°38.97S; 72°25.24W; Fontana, Bennett 2012: The Holocene), where human influence on vegetation is negligible. The western archipelago of Tierra del Fuego remained treeless for most of the Lateglacial period. Nothofagus may have survived the last glacial maximum at the eastern edge of the Magellan glaciers from where it spread southwestwards and established in the region at around 10,500 cal. yr BP. Nothofagus antarctica was likely the earlier colonizing tree in the western islands, followed shortly after by Nothofagus betuloides. At 9000 cal. yr BP moorland communities expanded at the expense of Nothofagus woodland. Simultaneously, Nothofagus species shifted to dominance of the evergreen Nothofagus betuloides and the Magellanic rain forest established in the region. Rapid and drastic vegetation changes occurred at 5200 cal. yr BP, after the Mt Burney MB2 eruption, including the expansion and establishment of Pilgerodendron uviferum and the development of mixed Nothofagus-Pilgerodendron-Drimys woodland. Scattered populations of Nothofagus, as they occur today in westernmost Tierra del Fuego may be a good analogue for Nothofagus populations during the Lateglacial in eastern sites. Climate, dispersal barriers and/or fire disturbance may have played a role controlling the postglacial spread of Nothofagus. Climate change during the Lateglacial and early Holocene was a prerequisite for the expansion of Nothofagus populations and may have controlled it at many sites in Tierra del Fuego. The delayed arrival at the site, with respect to the Holocene warming, may be due to dispersal barriers and/or fire disturbance at eastern sites, reducing the size of the source populations. The retreat of Nothofagus woodland after 9000 cal. yr BP may be due to competitive interactions with bog communities. Volcanic disturbance had a positive influence on the expansion of Pilgerodendron uviferum and facilitated the development of mixed Nothofagus-Pilgerodendron-Drimys woodland.

SINCOS: Sinking Coasts - Geosphere, Ecosphere and Anthroposphere of the Holocene Southern Baltic Sea - Part 1.4: Changing sea levels and (semi)terrestrial landscape development in the Baltic Sea coastral area, with special attention to the role of the Darss Sill

The research unit SINCOS, established by the Deutsche Forschungsgemeinschaft, has been started in September 2002. The general target is the development of a model of the relation between geo-system, eco-system, climate and socio-economic system for sinking coasts of tideless seas to be developed as an example for the southern Baltic Sea since the Atlantikum. Geoscientists (geologists, geomorphologists, geodesists), biologists (palaeobotanists, palaezoologists), climate researchers and archaeologists will collaborate in order to investigate the cause and effect relation between driving forces (climatic and geological processes) and the response of the natural and social environment in the coastal areas of a transgressive sea. The reconstruction of the Litorina transgression west and east of the Darss sill structure plays the central role. Seven projects under the roof of SINCOS will deal with the acquisition and interpretation of proxy-data in order to reconstruct the history of the southwestern Baltic Sea since 8.000 calendar years BC. In the frame of two projects data will be integrated and models will be developed that mirror the processes of interrelation of different spheres to be investigated. Depending on the varying degree of quantification between measurable variables and qualitative observations models will differ between statistical data exploration and deterministic differential equations. A 4D GIS plays the central role in modelling and data integration. Results will be presented as time-dependent regionalizations of geo-, eco-, and socio-economical parameters. Simulations of future relative sea level change scenarios based on models developed are planned.

ADVANCE-10K: Analysis of Dendrochronological Variability and Associated Natural Climates in Eurasia During the Last 10000 Years

Objective: To reconstruct a range of climate variables in different regions of northern Eurasia to enhance our knowledge of natural climate variability on a range of timescales within the last 10,000 years and advance our understanding of the mechanisms and forcings that have generated this variability. General Information: This project is focused in the area of dendroclimatology. The absolute dating control and seasonal growth of long tree-ring chronologies will be used to reconstruct a range of climate variables in different regions. The project encompasses extensive development of new densitometric chronologies in northern Siberia, part of ongoing work funded largely by The Swiss National Science Foundation. In addition, the major collections of European historical and sub-fossil oak ring-width data, principally from Great Britain, Sweden, Holland, Denmark, Germany and Poland, are being centralised, quality-controlled and entered into a common European tree-ring data base. Some modern chronology development is being undertaken to update these data and provide modern analogues for comparison with recent climate data. The project will reconstruct changes in temperature and precipitation-related variables over a range of temporal and spatial scales determined by the length, location and climate sensitivity of the available tree-ring data. This work will generate detailed individual maps of summer temperatures over several centuries across northern Siberia. These data will be interpreted in terms of large-scale atmospheric circulation patterns over western Europe and northern Eurasia and within the context of the large-scale general circulation of the Northern Hemisphere. Tree-growth and derived climate variability will be compared with (less well resolved) independent evidence of climate change in, and outside of, Europe, and with proxies of potential climate forcings such as volcanic, solar and Milankovitch changes throughout the Holocene. Evidence for the influence of ocean dynamics on European climates will be explored by comparing the statistical characteristics of the reconstructions with those of climate data produced by appropriate fully-coupled Ocean-Atmosphere General Circulation Models. Continuous regional-average timeseries will be produced spanning several millennia in specific regions of Sweden, Finland and Central Europe. These will allow an exploration of the evidence for contemporaneous, widespread and abrupt tree-growth changes that may indicate the effects of major environmental disruption potentially due to volcanic or cometary activity.

Klimawirkung und Boddenlandschaft- Teilprojekt: Holozaene Entwicklung ausgewaehlter Boddenlandschaften Mecklenburg-Vorpommerns unter besonderer Beruecksichtigung von Klima, Eustasie und Isostasie - Prozess, Modell, Prognos

Im Vorhaben werden in ausgewaehlten Bereichen der Vorpommerschen Boddenlandschaft (Fischland-Darss-Zingst und Schaabe auf Ruegen) land- und gewaesserseitige Bohrungen durchgefuehrt, an denen folgende Analysen vorgenommen werden sollen: Pollen-, Diatomeen und 14C-Analysen, Korngroessen-, Naehrstoffe- und Spurenelementanalysen. Auf dieser Grundlage werden Aussagen getroffen: - wie schnell wachsen die Nehrungen und wie spiegelt sich dies in den Sedimentationsbedingungen wieder, - wie haeufig werden die Nehrungen nach ihrer Schliessung durchbrochen und welche Schlussfolgerungen ergeben sich in Bezug auf die Hochwasserstatistik, - wie sind Nehrungsaufbau und die Umstellung des Gewaesserhaushaltes auf andere Trophie- und Salinitaetsbedingungungen gekoppelt,- zur Eustasie und Isostasie, - zu Kuestenveraenderungen und Schwankungen der Sedimentationsintensitaeten in Abhaengigkeit von Klimaaenderungen. Hierauf aufbauend werden zusammen mit anderen Vorhaben prognostische Aussagen zur Kuestenentwicklung gegeben. Ziel des Forschungsvorhabens ist die Darstellung der holozaenen Kuestenentwicklung der vorpommerschen Boddenlandschaft in Abhaengigkeit klimabedinger Wasserspiegelentwicklungen. Vor dem Hintergrund eines kuenftig steigenden Weltenergiespiegels sollte das Kuestenverhalten bei steigendem Meeresspielgeanstieg untersucht werden. Als Ergebnis konnte eine Standlinienverschiebungskurve fuer Ruegen abgeleitet werden, die eine phasenhafte, vom Klima gesteuerte Wasserspiegelentwicklung fuer die letzten 8000 Jahre zeigt. Das Kuestenverhalten wird ueber palaeogeographische Darstellungen sichtbar gemacht und in Bezug auf Wasserspiegelschwankugnen diskutiert.

Forschergruppe (FOR) 816: Biodiversity and Sustainable Management of a Megadiverse Mountain Ecosystem in South Ecuador, Forschergruppe FOR 816/2: Biodiversität und nachhaltiges Management eines megadiversen Hochgebirgsökosystems in Südecuador - D1: Analyse und Synthese von paläoökologischen Datensätzen zur Offenlegung von Mustern der Vegetation und Biodiversität in neotropischen Gebirgen und ihre Reaktionen auf Klima-, Feuer-, und Landnutzungsänderungen durch Zeit und Raum

Die südecuadorianischen Anden beherbergen eine außergewöhnlich hohe Artenvielfalt. Viele verschiedene Umweltfaktoren beeinflussen sich auf sehr limitiertem Raum und erschaffen so einzigartige und komplexe Ökosysteme. Dieses Gebiet ist jedoch auf Grund des zunehmenden menschlichen Einflusses durch die fortschreitende Intensivierung der Landnutzung und des globalen Wandels hochgefährdet. Wir wissen nur wenig über die paläoökologische Geschichte und Landschaftsdynamik dieses Gebiets. Die Information über das warum und wie einer Veränderung von Ökosystemen ist unerlässlich für die Entwicklung innovativer Strategien für Naturschutz und im Hinblick auf zukünftige Klimaveränderungen. In der vorliegenden Studie werden palynologische Analysen aus den südecuadorianischen Anden vorgestellt, die dazu beitragen, Muster und Prozesse heutiger und vergangener Ökosysteme zu beleuchten. Eine paläoökologische Studie des Quimsacocha-Vulkanbeckens auf der östlichen Erhebung der Westkordillere der südecuadorianischen Anden deckt Klima-, Vegetations- und Brandregimeveränderungen in dieser Region seit dem frühen Holozän auf. Das mittlere Holozän war eine Zeit starker Umweltveränderungen, verursacht durch ein trockenes und wohl wärmeres Klima. Während des späten Holozäns wechselten sich mehrere Kalt-und Warmphasen ab. Brände können seit dem frühen Holozän im Gebiet verzeichnet werden. Sie könnten ein erstes Zeichen menschlichen Einflusses darstellen. Mit anderen paläoökologischen Aufzeichnungen aus den südecuadorianischen Anden verglichene multivariate Analysen decken teilweise konstrastierende Entwicklungen an den verschieden Standorten auf, die vermutlich durch die Heterogenität der Umweltfaktoren zu erklären sind. Weiterhin wurden Studien zum Verhältnis von heutigem Pollenregen mit der Vegetation in der Podocarpus Nationalpark-Region durchgeführt, um die Pollenverbreitungsmuster innerhalb der verschiedenen Vegetationstypen, prämontaner Wald, unterer Bergwald, oberer Bergwald und Páramo, zu verstehen und damit eine bessere Grundlage zur Interpretation fossiler Pollendaten zu schaffen. Ein Vergleich von Abundanz und An-/Abwesenheitsdaten von Familien als taxonomischer Einheit für Pollen- und Vegetation zeigt, dass Diversität, Verbreitung und Häufigkeiten beider Datensätze gut miteinander in Verbindung gebracht werden können. Dennoch werden die Muster durch variierende Anteile von durch Ferntransport eingetragenen Pollenkörnern sowie durch unterschiedliche Pollenproduktivität verschiedener Taxa und heterogene Windsysteme beeinflusst. Analysen der Pollenakkumulationsraten, die über drei Jahre erfasst wurden, lassen auf eine geringe inter-annuelle aber hohe räumliche Variation in den Daten schließen. (Text gekürzt)

Natural and anthropogenic mineral aerosols from ice and sediment Alpine records: Climatic, stratigraphic, and environmental implications.

The investigation of sediment cores from two of the largest freshwater lakes from Western Europe (lakes Geneva and Lucerne) demonstrated that natural sources of trace elements dominated before the European industrial revolution. The heavy metal pollution (e.g. lead, mercury) highly increased following the industrialization of Switzerland after 1850. The implementation of wastewater treatment plants (WWTPs) in the 1960s significantly decreased the metal pollution at the deepwater sites. By contrast, the Vidy Bay of Lake Geneva where are released the WWTP of the city of Lausanne since 1964 was highly contaminated by heavy metals due to the WWTP emissions. Lead isotopic composition furthermore highlighted the industrial pollution sources over the last 200 years. During the twentieth century, industrial releases multiplied by 10 times heavy metal fluxes to hydrological systems located on both sides of the Alps. The remote and small high altitude lake Meidsee (2661 m a.s.l. in the Southwestern Alps) revealed the strong increase in anthropogenic trace metal deposition during the Greek and Roman Empires (ca 300 BC to AD 400), the Late Middle Ages (ca AD 1400), and the Early Modern Europe (after ca AD 1600). The greatest increases in anthropogenic metal pollution were evidenced after the industrial revolution of ca AD 1850, especially in Lake Lucerne where industrial activities and the steamboat navigation released high amounts of fossil fuel combustion residues and heavy metals. The elemental and isotopic composition of sedimentary organic matter from the high-altitude Lake Meidsee provided additional information about the high-altitude Alpine landscape evolution since the Late Pleistocene/Holocene deglaciation in the Swiss Southwestern Alps; and indicated the predominant deposition of algal-derived organic matter with limited input of terrestrial organic matter before the Holocene Climatic Optimum (between 7.0 and 5.5 years ago). This research also investigated faecal indicator bacteria (Escherichia coli and Enterococcus), multiple antibiotic resistant and antibiotic resistance genes, in sediment profiles from different parts of Lake Geneva (Switzerland) over the last decades. Results showed that the WWTP input constituted the main source of pollution for several contaminants, including heavy metals, antibiotics, and antibiotic-resistant bacteria. The Bay of Vidy of Lake Geneva can therefore be considered as a reservoir of bacteria multiple resistance genes. Hence, the human-induced eutrophication in the 1970s highly enhanced the sediment microbial activity, and therein the spreading of antibiotic resistant bacteria and genes in this aquatic environment used to supply drinking water in a highly populated area.

Schwerpunktprogramm (SPP) 1266: Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC), Sub project: Dynamics of Mid-latitude/ Mediterranean climate during the last 150 ka: Black Sea /Northern Anatolian Paleoenvironmental Reconstructions (DynNAP)

As an isolated marginal sea, the Black Sea reacted particularly sensitive to paleoclimatic and paleoenvironmental changes and on both global and regional scales. In spite of its unique potential for high resolution paleoclimate reconstructions, late Quaternary sediment sequences of the Black Sea have only subordinately been studied with respect to paleoclimatic questions. This is somewhat surprising considering the key-geographic location of the Black Sea, where climate is strongly affected by two major climate systems; the North Atlantic/Siberian pressure system in winter and the Indian monsoon in summer. Highly-resolved and precisely dated paleoclimate records are crucial for reconstructing past regional climate variability, which can then be compared to paleoclimate records from the North Atlantic, Europe and the Indian monsoon domain. Several core sites in the Black Sea along the North-Anatolian rim can provide records of vegetation dynamics and changing precipitation regimes in the Anatolian hinterland as well as paleoceanographic/ paleolimnologic data of environmental changes in the marine/limnic Black Sea system itself. Uranium-series dated stalagmites from Sofular Cave located at the Black Sea coast in north-western Turkey will provide, as terrestrial counterpart, long complementary paleorecords of changes in vegetation and precipitation. When combined, such records will allow us to better quantify the far-field effects of North Atlantic climate and Indian monsoon during the Holocene, Eemian and the last two glacial/interglacial transitions (T1 and T2).

1 2 3 4 5 6