Correlating the Ancient Maya and Modern European Calendars with High-Precision AMS 14C Dating

The reasons for the development and collapse of Maya civilization remain controversial and historical events carved on stone monuments throughout this region provide a remarkable source of data about the rise and fall of these complex polities. Use of these records depends on correlating the Maya and European calendars so that they can be compared with climate and environmental datasets. Correlation constants can vary up to 1000 years and remain controversial. We report a series of high-resolution AMS C-14 dates on a wooden lintel collected from the Classic Period city of Tikal bearing Maya calendar dates. The radiocarbon dates were calibrated using a Bayesian statistical model and indicate that the dates were carved on the lintel between AD 658-696. This strongly supports the Goodman-Martinez-Thompson (GMT) correlation and the hypothesis that climate change played an important role in the development and demise of this complex civilization.

Inverse modelling of the 14C bomb pulse in stalagmites to constrain the dynamics of soil carbon cycling at selected European cave sites

The decomposition of soil organic matter (SOM) is temperature dependent, but its response to a future warmer climate remains equivocal. Enhanced rates of decomposition of SOM under increased global temperatures might cause higher CO2 emissions to the atmosphere, and could therefore constitute a strong positive feedback. The magnitude of this feedback however remains poorly understood, primarily because of the difficulty in quantifying the temperature sensitivity of stored, recalcitrant carbon that comprises the bulk (>90%) of SOM in most soils. In this study we investigated the effects of climatic conditions on soil carbon dynamics using the attenuation of the 14C ‘bomb’ pulse as recorded in selected modern European speleothems. These new data were combined with published results to further examine soil carbon dynamics, and to explore the sensitivity of labile and recalcitrant organic matter decomposition to different climatic conditions. Temporal changes in 14C activity inferred from each speleothem was modelled using a three pool soil carbon inverse model (applying a Monte Carlo method) to constrain soil carbon turnover rates at each site. Speleothems from sites that are characterised by semi-arid conditions, sparse vegetation, thin soil cover and high mean annual air temperatures (MAATs), exhibit weak attenuation of atmospheric 14C ‘bomb’ peak (a low damping effect, D in the range: 55–77%) and low modelled mean respired carbon ages (MRCA), indicating that decomposition is dominated by young, recently fixed soil carbon. By contrast, humid and high MAAT sites that are characterised by a thick soil cover and dense, well developed vegetation, display the highest damping effect (D = c. 90%), and the highest MRCA values (in the range from 350 ± 126 years to 571 ± 128 years). This suggests that carbon incorporated into these stalagmites originates predominantly from decomposition of old, recalcitrant organic matter. SOM turnover rates cannot be ascribed to a single climate variable, e.g. (MAAT) but instead reflect a complex interplay of climate (e.g. MAAT and moisture budget) and vegetation development.

Eine Million Algerier lernen im 20. Jahrhundert zu leben. Umsiedlungslager und Zwangsmodernisierung im Algerienkrieg 1954–1962

Als eines der erstaunlichsten Merkmale des algerisch-französischen Unabhängigkeitskriegs 1954-1962 darf die Kombination von militärischer Aufstandsbekämpfung und zivilen Reformprojekten gelten. Diese Verschränkung lässt sich an keinem Aspekt dieses Krieges so deutlich beobachten wie an der französischen Umsiedlungspolitik. Bis zu drei Millionen Menschen wurden während des Krieges von der französischen Armee gewaltsam aus ihren Dörfern vertreiben und in eigens angelegte Sammellager, die «camps de regroupement», umgesiedelt. Was als rein militärische Maßnahme begann, entwickelte sich schnell zu einem gewaltigen ländlichen Entwicklungsprogramm. Durch das Versprechen einer umfassenden Modernisierung aller Lebensbereiche im Schnellverfahren sollten die Insassen der Lager zu loyalen Anhängern des Projekts eines französischen Algeriens gemacht werden. Die «camps de regroupement» lassen sich als Modernisierungslaboratorien beschreiben, in denen sich scheinbar widersprüchliche Elemente wie Entwicklungshilfe mit äußerst rigider Bevölkerungskontrolle und totalitär anmutenden Maßnahmen des social engineering zu einem einzigartigen Ensemble verbanden. [ABSTRACT FROM AUTHOR]