Irreversible impact of past land use on forest soils and biodiversity.

Abstract. In western Europe, forest area has been expanding rapidly since the 19th century, mainly on former agricultural land. Previous studies show that plant diversity differs between these recent forests and ancient forests that were already forested at the time of first national cadastral surveys, around 1800. Here, we investigated the duration of such agricultural aftereffects. In northeastern France, large areas were deforested during the Roman occupation and thereafter abandoned to forest. In one such forest that was farmed during the period AD 50-250, we show that species richness and plant communities vary according to the intensity of former agriculture. These variations are linked to longterm changes of chemical and structural soil properties. Hence, we suggest that such effects of past agricultural land use on forest biodiversity may be irreversible on an historical time scale

Contributions au colloque La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2

Ce document contient une partie des contributions au colloque "La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2" organisé par la cour d'appel de Toulouse et l'Institut de Droit Privé de l'Université Toulouse 1 Capitole : - Plaquette de présentation du colloque - Propos introductifs de M. Defix - Table ronde "la tentative de conciliation obligatoire préalable à la saisine du juge", interventions de Mme Leclercq et Mr Brugel - Table ronde "la tentative de conciliation obligatoire devant le juge", interventions de Mme Bruggeman et Me Capéla - Table ronde "la conciliation devant le conseil de prud'hommes", interventions de Mme Dupouey-Dehan et Mr Made

Contributions au colloque La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2

Ce document contient une partie des contributions au colloque "La conciliation dans le ressort de la cour d'appel de Toulouse, Acte 2" organisé par la cour d'appel de Toulouse et l'Institut de Droit Privé de l'Université Toulouse 1 Capitole : - Plaquette de présentation du colloque - Propos introductifs de M. Defix - Table ronde "la tentative de conciliation obligatoire préalable à la saisine du juge", interventions de Mme Leclercq et Mr Brugel - Table ronde "la tentative de conciliation obligatoire devant le juge", interventions de Mme Bruggeman et Me Capéla - Table ronde "la conciliation devant le conseil de prud'hommes", interventions de Mme Dupouey-Dehan et Mr Made

Genetic differentiation and admixture between sibling allopolyploids in the Dactylorhiza majalis complex

Allopolyploidization often happens recurrently, but the evolutionary significance of its iterative nature is not yet fully understood. Of particular interest are the gene flow dynamics and the mechanisms that allow young sibling polyploids to remain distinct while sharing the same ploidy, heritage and overlapping distribution areas. By using eight highly variable nuclear microsatellites, newly reported here, we investigate the patterns of divergence and gene flow between 386 polyploid and 42 diploid individuals, representing the sibling allopolyploids Dactylorhiza majalis s.s. and D. traunsteineri s.l. and their parents at localities across Europe. We make use in our inference of the distinct distribution ranges of the polyploids, including areas in which they are sympatric (that is, the Alps) or allopatric (for example, Pyrenees with D. majalis only and Britain with D. traunsteineri only). Our results show a phylogeographic signal, but no clear genetic differentiation between the allopolyploids, despite the visible phenotypic divergence between them. The results indicate that gene flow between sibling Dactylorhiza allopolyploids is frequent in sympatry, with potential implications for the genetic patterns across their entire distribution range. Limited interploidal introgression is also evidenced, in particular between D. incarnata and D. traunsteineri. Altogether the allopolyploid genomes appear to be porous for introgression from related diploids and polyploids. We conclude that the observed phenotypic divergence between D. majalis and D. traunsteineri is maintained by strong divergent selection on specific genomic areas with strong penetrance, but which are short enough to remain undetected by genotyping dispersed neutral markers.UE FWF; P22260UE: Y66

Subdivisions de la forêt de bois de couleur à l'île de la Réunion

International audienc

Forest seed banks along an intensity gradient of ancient agriculture

Recently, forest seed banks were proven to not only reflect former (decades-old) but also ancient (centuries-old) land use. Yet, as land-use intensity determines the magnitude of seed-bank changes in recent forests, this study aims to identify whether an ancient land-use gradient would also be reflected in the seed bank. On a forested 1600-year-old archaeological site, five different land-use intensities were mapped and sampled. Apart from seed density, species richness and composition, functional seed-bank types, defined by nine seed-bank-related plant traits, were related to the land-use intensity gradient. The land-use gradient from gardens to undisturbed sites was still clearly reflected in the soil seed bank. Six emergent functional seed-bank types, characterized by specific plant traits, changed significantly in abundance, parallel to the land-use gradient. In particular, dispersal agent (and related traits) proved an important explanatory trait of present (functional) seed-bank patterns. Poor dispersers (large and heavy seeds) were not found in the intensively used areas, contrary to animal-dispersed species. Wind-dispersers may have been inhibited in the extension of their distribution by recruitment bottlenecks (low seed production) and/or competitive exclusion. Additionally, the agricultural land-use probably introduced ruderal species into the seed bank of the most intensively used areas, yielding a simultaneous increase in vegetation-seed-bank dissimilarity with land-use intensity, eliminating present vegetation as a driver behind the differences over the seed-bank gradient. We conclude by arguing how coppice-with-standards management possibly maintained the seed-bank gradient

Quelques évolutions récentes des relations entre archéologie, forêt et environnement

National audienc