Multiple introductions boosted genetic diversity in the invasive range of black cherry (Prunus serotina; Rosaceae)

Background and Aims Black cherry (Prunus serotina) is a North American tree that is rapidly invading European forests. This species was introduced first as an ornamental plant then it was massively planted by foresters in many countries but its origins and the process of invasion remain poorly documented. Based on a genetic survey of both native and invasive ranges, the invasion history of black cherry was investigated by identifying putative source populations and then assessing the importance of multiple introductions on the maintenance of gene diversity. Methods Genetic variability and structure of 23 populations from the invasive range and 22 populations from the native range were analysed using eight nuclear microsatellite loci and five chloroplast DNA regions. Key Results Chloroplast DNA diversity suggests there were multiple introductions from a single geographic region (the north-eastern United States). A low reduction of genetic diversity was observed in the invasive range for both nuclear and plastid genomes. High propagule pressure including both the size and number of introductions shaped the genetic structure in Europe and boosted genetic diversity. Populations from Denmark, The Netherlands, Belgium and Germany showed high genetic diversity and low differentiation among populations, supporting the hypothesis that numerous introduction events, including multiple individuals and exchanges between sites, have taken place during two centuries of plantation. Conclusions This study postulates that the invasive black cherry has originated from east of the Appalachian Mountains (mainly the Allegheny plateau) and its invasiveness in north-western Europe is mainly due to multiple introductions containing high numbers of individual

Coexistence et confrontation des modèles agricoles et alimentaires

De nouveaux modèles agricoles et alimentaires se déploient dans les territoires en réponse aux critiques des formes anciennes et pour faire face à de nouveaux enjeux. Ils incarnent des archétypes de la diversité observée, des projets d’acteurs ou bien de nouvelles normes. Les auteurs analysent ici des situations de coexistence et de confrontation de modèles agricoles et alimentaires selon quatre dimensions majeures du développement territorial : la tension entre spécialisation et diversification, l’innovation, l’adaptation et la transition alimentaire. Une série de travaux conceptuels et d’études de cas en France et de par le monde permet de comprendre les interactions entre ces modèles (confrontation, complémentarité, coévolution, hybridation, etc.), au-delà de la caractérisation de leur diversité et de l’évaluation de leurs performances relatives. La coexistence et la confrontation de ces modèles renforcent leur capacité de changement radical. L’ouvrage souligne les questions originales du cadre d’analyse, ses défis méthodologiques et les conséquences attendues pour l’accompagnement du développement agricole et alimentaire dans les territoires ruraux et urbains. Il est destiné aux chercheurs, enseignants, étudiants et professionnels intéressés par le développement territorial

Vers l’émergence d’une gestion stratégique des ressources humaines dans les Établissements et Services d’Aide par le Travail (Esat) ?

International audienc

Mapping farming practices in Belgian intensive cropping systems from Sentinel-1 SAR times-series

The environmental impact of the so-called conventional farming system calls for new farming practices reducing negative externalities. Emerging farming practices such as no-till and new inter-cropping management are promising tracks. The development of methods to characterize crop management across an entire region and to understand their spatial dimension offers opportunities to accompany the transition towards a more sustainable agriculture. This research takes advantage of the unmatched polarimetric and temporal resolutions of Sentinel-1 SAR Cband to develop a method to identify farming practices at the parcel level. To this end, the detection of changes in backscattering due to surface roughness modification (tillage, inter-crop cover destruction ...) is used to detect the farming management. The final results are compared to a reference dataset collected through an intensive field campaign. Finally, the performances are discussed in the perspective of practices monitoring of cropping systems through remote sensing

The use of hyperspectral imagery for digital soil mapping in mediterranean areas

Hyperspectral imagery is considered as a promising source of data to overcome the lack of soil information that often hamper digital soil mapping. We have tested it in the vineyard plain of Languedoc (southern France) using an 5×5m resolution HYMAP image and 52 calibration-validation points. Satisfactory predictions of clay content and calcium carbonate (CaCO3) content were first obtained from HYMAP spectra over bare soils, partial least-squares regression performing better than continuum removal technique. These predictions were however less precise than using laboratory spectra. An examination of the possible factors that could explain this decrease showed that calibration uncertainties of the HYMAP sensor and of atmospheric effects were largely predominant. Secondly, since the HYMAP image was largely covered by vegetation with few pure bare soil pixels, an interpolation-aggregation procedure was proposed to obtain a 100×100m digital soil map of the whole study area from a set of scattered bare soil fields with hyperspectral soil characterization. Interpolation was performed by a conditional simulation algorithm to estimate the within pixel soil pattern parameters. Validation results showed that satisfactory estimates of local means can be obtained whereas the variations of local variances were only partly represented.In the near future, a new proof-of-concept zone will be implemented in Tunisia to confirm these encouraging results and to examine how hyperspectral imagery can be used in association with soil legacy data and digital terrain models to produce digital maps of soil properties in the Mediterranean areas

Les empreintes de dinosaures de Mende : de la fouille à l'étude paléontologique.

International audienceDisparus il y a près de 65 millions d’années, les dinosaures fascinent petits et grands, amateurs et scientifiques. Cependant, ces « terribles lézards » suscitent encore aujourd’hui beaucoup d’interrogations. C’est notamment le cas des dinosaures qui peuplaient l’Aveyron et la Lozère il y a 200 millions d’années, au Jurassique inférieur. Les ossements de dinosaures étant extrêmement rares dans les roches de cette époque, l’étude de leurs empreintes est primordiale. La région des causses est d’ailleurs un des plus importants secteurs d’Europe pour l’étude des traces de pas. C’est dans ce contexte qu’une nouvelle dalle à empreintes a récemment été découverte à Mende, en Lozère. Richement illustré, cet ouvrage décrit l’histoire de la découverte, la fouille et les résultats de l’étude scientifique de ce site paléontologique exceptionnel