Les enseignements morpho-paysagers des enregistrements de la centuriation romaine en Tunisie

En Tunisie, l’ancien découpage territorial de la centuriation romaine était très important aussi bien par son étendue que par sa précision. Ces dernières décennies, les traces de cette centuriation régressent du fait des aménagements territoriaux. Pourtant, elles imprègnent toujours les paysages d’une marque profonde et représentent un remarquable enregistrement de données morpho-dynamiques et morpho-pédologiques. L’étude des sites au centre-est de la Tunisie montre que les ruissellements sont guidés par les vestiges du cadastre antique. La trame centuriale se lit également à travers des tonalités claires ou sombres des sols. La prospection au sol, l’échantillonnage et les analyses de laboratoire offrent autant d’éléments de réponses. La centuriation de la Tunisie atteste de l’emprise romaine sur le milieu. En effet, bien plus qu’une simple limite de champs, la centuriation semble avoir d’autres fonctionnalités, telles que la bonne gestion de l’eau et la lutte contre l’érosion, preuves de la prospérité romaine

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Dynamique lacustre Holocène dans la sebkha al Kalbiyya(Tunisie centre orientale)

Une carotte profonde de 31,47 m a été prélevée dans la sebkha al Kalbiyya en Tunisie centre orientale. Le présent travail se focalise sur la section médiane riche en malacofaune lacustre, entre 11,18 et 16,19 m de profondeur. Les premiers résultats obtenus sur le fonctionnement, les fluctuations et les récurrences lacustres holocènes de la sebkha sont présentés. La description lithoséquentielle détaillée de la section a conduit à identifier trois grands types de faciès et d’environnements de dépôt (lacustre, palustre-lacustre et palustre-sebkha) et à définir onze phases majeures de sédimentation associées à l’alternance de trois systèmes de fonctionnement paléohydrologique de type lac pérenne, lac temporaire et lac temporaire-sebkha. Ces données, couplées à trois datations radiocarbone, ont permis de cerner deux périodes de récurrences lacustres d’amplitude différente. La première période, entre 6 971 et 5 596 cal BP, est de grande amplitude, quand la seconde, entre 5 596 et 4 970 cal BP, est de faible amplitude.A 31.47 m long continuous core has been retrieved from sebkha al Kalbiyya in eastern central Tunisia. The study focuses on the 11.18 - 16.19 m interval of the core, and its rich lacustrine malacological content. Based on the preliminary results, the paper aims to discuss the Holocene sebkha function as a lake, associated to fluctuations and recurrences of lacustrine deposits. The detailed lithosequential description of the section has led to identify three major types of facies and depositional environments (lacustrine, palustrine-lacustrine and palustrine-sebkha) and to define eleven major sedimentation phases associated with the alternation of three paleohydrological systems of perennial lake, temporary lake and temporary lake-sebkha types. These data coupled with three radiocarbon datings allowed to distinguish two periods of lacustrine recurrences of different amplitude. The first period, between 6 971 and 5 596 cal BP, is of great amplitude, while the second, between 5 596 and 4 970 cal BP, is of low amplitude

Early oleiculture or native wild Olea in eastern Maghreb: new pollen data from the sebkha-lagoon Halk el Menjel (Hergla, Central Tunisia)

International audiencePollen analyses from the sebkha-lagoon Halk El Menjel document the vegetation history in Central Tunisia, linked to climate change since the Middle Holocene. Steppes are the main biomes developed under semi-arid conditions between 4965 ± 35 and 3410 ± 40 BP. At 4365 ± 50 BP Pistacia is replaced by Olea and high representation of Olea pollen grains are reported between 4365 ± 50 and 3410 ± 40 BP, illustrating a humid episode at the Mid-to-Late Holocene transition. Thus, the semi-arid area of Central Tunisia could correspond to the native biome for oleasters at the beginning of the Late Holocene. Early olive cultivation is not yet evidenced in the Neolithic sites of the eastern Maghreb, and the Phoenicians are assumed to have introduced olive cultivars in Tunisia. However, an early cultivation of Olea from local native oleaster and dissemination of native cultivars in Central Tunisia can be hypothesised even if it has to be still demonstrated with further archaeological and archaeobotanical evidence