Les frontières culturelles et politiques du monde mycénien

Le bassin oriental de la Méditerranée à l’âge du bronze égéen est un ensemble hétérogène où s’entremêlent plusieurs cultures : Égyptiens, Hittites, Minoens et Mycéniens se côtoient et interagissent à divers degrés. Un examen méticuleux des sources archéologiques et épigraphiques permet de mettre un peu d’ordre à cette mosaïque chaotique afin de mieux apprécier les interactions entre ces cultures. La culture mycénienne est celle à laquelle s’intéresse particulièrement cette présente étude. Bien que son coeur soit unanimement localisé en Grèce continentale, la culture mycénienne se répand également de l’Italie jusqu’au Levant et de la Thrace à l’Égypte. Selon l’importance et la nature des vestiges, l’archéologie ordonne en trois catégories les régions où se retrouve la culture mycénienne, alors que les sources épigraphiques hittites et égyptiennes permettent de remettre en question la société mycénienne et de localiser les frontières politiques de cette culture.The Eastern Mediterranean region in the late Bronze Age is a heterogeneous entity composed of several interwoven cultures: Egyptians, Hittites, Minoans and Mycenaeans mingle and interact on many levels. A meticulous survey of the archaeological and epigraphic evidence can restore some order in this chaotic picture in order to clarify the various interactions between these cultures. This study focuses especially on the Mycenaean culture. Although mainland Greece is unanimously considered as the core location of this culture, Mycenaean artefacts are found from Italy to the Levant and from Thrace to Egypt. According to the importance and nature of these artefacts, archaeology organizes the regions penetrated by Mycenaean culture in three classes, while Egyptian and Hittite documents challenge our conception of the organization of Mycenaean society and the localisation of its borders

Rapidité de la vitesse d'altération des minéraux du sol en conditions ferrallitiques : méthode des minéraux-test

Les minéraux des sols sont soumis à des dissolutions et reprécipitations en fonction des conditions de milieu, et en particulier de l'activité biologique. Pour déterminer la cinétique des réactions mises en jeu dans le recyclage des éléments chimiques, des sachets de minéraux test contenant séparément de la gibbsite, deux types de kaolinite et un verre siliceux, ont été introduits dans les horizons supérieurs d'un sol ferrallitique de forêt amazonienne. Au bout de 6 mois, toutes les phases implantées ont été altérées, et d'autres minéraux, oxy-hydroxydes de fer et de titane, sont apparus. La réactivité des minéraux secondaires avec les conditions de milieu est donc rapide à l'échelle des temps pédologiques dans les sols étudiés. (Résumé d'auteur

Changes of the forest-savanna boundary in Brazilian Amazonia during the holocene revealed by stable isotope ratios of soil organic carbon

The possibility of ecosystem boundary changes in northern Brazilian Amazonia during the Holocene period was investigated using soil organic carbon isotope ratios. Determination of past and present fluctuations of the forest-savanna boundary involved the measurement of natural 13C isotope abundance, expressed as delta 13C, in soil organic matter (SOM). SOM 13C analyses and radiocarbon dating of charcoal fragments were carried out on samples derived from soil profiles taken along transects perpendicular to the ecotonal boundary. SOM delta 13C values in the upper soil horizons appeared to be in equilibrium with the overlying vegetation types and did not point to a movement of the boundary during the last decades. However, delta 13C values obtained from deeper savanna and forest soil layers indicated that the vegetation type has changed in the past. In current savanna soil profiles, we observed the presence of mid-Holocene charcoals derived from forest species : fire frequency at that time was probably greater, and more extensive savanna may have resulted. Isotope data and the presence of these charcoals thus suggest that the forest-savanna boundary has shifted significantly in the recent Holocene period, forest being more extensive during the early Holocene than today. During the middle Holocene, the forest could have strongly regressed, and fires appeared, with a maximum development of the savanna vegetation. At the beginning of the late Holocene, the forest may have invaded a part of this savanna, and fires occurred again. (Résumé d'auteur

Tree Regeneration Under Different Land-Use Mosaics in the Brazilian Amazon’s “Arc of Deforestation”

We studied the tree-regeneration patterns in three distinct agricultural settlements in the Eastern Amazon to test the influence of land-use mosaics. The following questions are addressed: are the floristic structure and composition of regenerating trees affected by the various land-use types applied in the agricultural settlements? Do tree-regeneration patterns respond similarly to distinct land-use mosaics? Is there a relationship between tree regeneration and soil characteristics among the land-use types? The regeneration was inventoried at 45 sampling points in each settlement. At each sampling point, fourteen soil variables were analyzed. Nine different land-use types were considered. The floristic structure and composition of the settlements showed differences in the density of individuals and species and high species heterogeneity among the land-use types. The maximum Jaccard similarity coefficient found between land-use types was only 29 %. Shade-tolerant species were the most diverse functional group in most land-use types, including pasture and annual crops, ranging from 91 % of the number of species in the conserved and exploited forests of Travessão 338-S to 53 % in the invaded pastures of Maçaranduba. The land-use types influenced significantly the floristic structure and composition of regenerating trees in two agricultural settlements, but not in third the settlement, which had greater forest cover. This finding demonstrates that the composition of each land-use mosaic, established by different management approaches, affects regeneration patterns. Tree regeneration was related to soil characteristics in all mosaics. Preparation of the area by burning was most likely the determining factor in the differences in soil characteristics between forests and agricultural areas. © 2015, Springer Science+Business Media New York