104 resultados para World and global history
Resumo:
Analyses of pollen, macrofossils and microscopic charcoal in the sediment of a small sub-alpine lake (Karakol, Kyrgyzstan) provide new data to reconstruct the vegetation history of the Kungey Alatau spruce forest during the late-Holocene, i.e. the past 4,000 years. The pollen data suggest that Picea schrenkiana F. and M. was the dominant tree in this region from the beginning of the record. The pollen record of pronounced die-backs of the forests, along with lithostratigraphical evidence, points to possible climatic cooling (and/or drying) around 3,800 cal year B.P., and between 3,350 and 2,520 cal year B.P., with a culmination at 2,800-2,600 cal B.P., although stable climatic conditions are reported for this region for the past 3,000-4,000 years in previous studies. From 2,500 to 190 cal year B.P. high pollen values of P. schrenkiana suggest rather closed and dense forests under the environmental conditions of that time. A marked decline in spruce forests occurred with the onset of modern human activities in the region from 190 cal year B.P. These results show that the present forests are anthropogenically reduced and represent only about half of their potential natural extent. As P. schrenkiana is a species endemic to the western Tien Shan, it is most likely that its refugium was confined to this region. However, our palaeoecological record is too recent to address this hypothesis thoroughly.
Resumo:
Most desertification research focuses on degradation assessments without putting sufficient emphasis on prevention and mitigation strategies, although the concept of Sustainable Land Management (SLM) is increasingly being acknowledged. A variety of already applied conservation measures exist at the local level, but they are not adequately recognised, evaluated and shared, either by land users, technicians, researchers, or policy makers. Likewise, collaboration between research and implementation is often insufficient. The aim of this paper is to present a new methodology for a participatory process of appraising and selecting desertification mitigation strategies, and to present first experiences from its application in the EU-funded DESIRE project. The methodology combines a collective learning and decision approach with the use of evaluated global best practices. In three parts, it moves through a concise process, starting with identifying land degradation and locally applied solutions in a stakeholder workshop, leading to assessing local solutions with a standardised evaluation tool, and ending with jointly selecting promising strategies for implementation with the help of a decision support tool. The methodology is currently being applied in 16 study sites. Preliminary analysis from the application of the first part of the methodology shows that the initial stakeholder workshop results in a good basis for stakeholder cooperation, and in promising land conservation practices for further assessment. Study site research teams appreciated the valuable results, as burning issues and promising options emerged from joint reflection. The methodology is suitable to initiate mutual learning among different stakeholder groups and to integrate local and scientific knowledge.
Resumo:
More than 500 endemic haplochromine cichlid species inhabit Lake Victoria. This striking species diversity is a classical example of recent explosive adaptive radiation thought to have happened within the last similar to 15,000 years. In this study, we examined the population structure and historical demography of 3 pelagic haplochromine cichlid species that resemble in morphology and have similar niche, Haplochromis (Yssichromis) laparogramma, Haplochromis (Y.) pyrrhocephalus, and Haplochromis (Y.) sp. "glaucocephalus". We investigated the sequences of the mitochondrial DNA control region and the insertion patterns of short interspersed elements (SINEs) of 759 individuals. We show that sympatric forms are genetically differentiated in 4 of 6 cases, but we also found apparent weakening of the genetic differentiation in areas with turbid water. We estimated the timings of population expansion and species divergence to coincide with the refilling of the lake at the Pleistocene/Holocene boundary. We also found that estimates can be altered significantly by the choice of the shape of the molecular clock. If we employ the nonlinear clock model of evolutionary rates in which the rates are higher towards the recent, the population expansion was dated at around the event of desiccation of the lake ca. 17,000 YBP. Thus, we succeeded in clarifying the species and population structure of closely related Lake Victoria cichlids and in showing the importance of applying appropriate clock calibrations in elucidating recent evolutionary events. (C) 2009 Elsevier B.V. All rights reserved.
Resumo:
Over the last ~20 years, soil spectral libraries storing near-infrared reflectance (NIR) spectra from diverse soil samples have been built for many places, since almost 10 years also for Tajikistan. Many calibration approaches have been reported and used for prediction from large and heterogeneous libraries, but most are hampered by the high diversity of the soils, where the mineral background is heavily influencing spectral features. In such cases, local learning strategies have the advantage of building locally adapted calibrations, which can deal better with nonlinearities. Therefore, it was our major aim to identify the most efficient approach to develop an accurate and stable locally weigthed calibration model using a spectral library compiled over the past years. Keywords: Tajikistan, Near-Infrared spectroscopy (NIRS), soil organic carbon, locally weighted regression, regional and local spectral library.
Resumo:
Primary control is defined as changing the world to fit the self, while secondary control is defined as changing the self to fit the world. To understand why different individuals prefer different kinds of control processes, we proposed a research project looking at US, German and Indian young adults. We hypothesize that theories of self and the world (fixed vs. malleable; Dweck, 1999) affect the prevailing mode of control used. Furthermore, adolescents’ cultural background is assumed to affect their self-world theories as well as the adaptiveness of specific modes of control. For example, in the US, where the self is tended to be seen as fixed and the world as malleable, primary control prevails and is more adaptive than secondary control while the reverse is expected for India. We present the theoretical outline and methodology of the study as well as first results.
Resumo:
The end of the Last Glacial Maximum (Termination I), roughly 20 thousand years ago (ka), was marked by cooling in the Northern Hemisphere, a weakening of the Asian monsoon, a rise in atmospheric CO2 concentrations and warming over Antarctica. The sequence of events associated with the previous glacial–interglacial transition (Termination II), roughly 136 ka, is less well constrained. Here we present high-resolution records of atmospheric CO2 concentrations and isotopic composition of N2—an atmospheric temperature proxy—from air bubbles in the EPICA Dome C ice core that span Termination II. We find that atmospheric CO2 concentrations and Antarctic temperature started increasing in phase around 136 ka, but in a second phase of Termination II, from 130.5 to 129 ka, the rise in atmospheric CO2 concentrations lagged that of Antarctic temperature unequivocally. We suggest that during this second phase, the intensification of the low-latitude hydrological cycle resulted in the development of a CO2 sink, which counteracted the CO2 outgassing from the Southern Hemisphere oceans over this period.