Effet du pâturage ovin sur les communautés végétales des marais salés de la baie de Somme (France)

The use of domestic animal grazing to manage temperate salt-marsh ecosystems is still debated and requires further field investigations. The effects of sheep grazing on plant community were studied in the salt-marshes of the Bay of Somme (France). We compared vegetation characteristics between two sets of grazed and ungrazed 1m2-plots. We tested for differences in species composition using pair-wise Multi-Response Permutation Procedures (MRPP), used an Indicator Species Analysis (ISA) to distinguish species indicator of grazed and ungrazed areas and described community structures with species rank-abundance curves. Differences in species richness and plant height and biovolume were tested using Mann-Whitney tests. MRPP showed that plant community composition differed significantly between grazed plots, dominated by Puccinellia maritima and Festuca rubra ssp. litoralis, and ungrazed plots, dominated by Halimione portulacoides (T = -60.37; A = 0.10; p < 0.0001). Nine species were indicator of grazed areas and four of ungrazed areas. Grazed communities had higher species richness (3.5 ± 0.2 species.m-2) than ungrazed communities (2.9 ± 0.1 species.m-2; p < 0.001). This significant difference is noteworthy in salt-marsh systems usually characterized by low contrasts of species richness. In grazed plots, vegetation height and biovolume were lower but vegetation cover was higher than in ungrazed plots. According to the identity of the species, plants lost 16.7% to 86.3% of their height under grazing pressure. The species showing the highest decrease in height (> 50%) were mainly pioneer halophytes and grasses. Aster tripolium, Suaeda maritima var. maritima, Halimione portulacoides, Spergularia marina were heavily damaged or browsed and lost more than 90% of their biovolume in grazed area. Through cascading effects, sheep grazing reduces the vegetation height, controls the identity of dominant species, relaxes competitive interaction for light between species and, finally, positively influences plant species richness. We thus recommend a moderate and extensive sheep grazing to manage European salt-marshes dominated by few highly competitive plant species. Finally, we categorized species according to their height loss percentage under grazing and their indicator value from ISA to provide a field tool to help the shepherds to estimate the impact of grazing on salt-marsh plantsL'utilisation du pâturage par les animaux domestiques pour gérer les écosystèmes des marais salés est toujours débattue et demande plus d'investigations de terrain. L'effet du pâturage sur les communautés végétales a été étudié dans des marais salés de la Baie de Somme (France). Nous avons comparé les caractéristiques de la végétation entre deux lots de relevés pâturés et non pâturés. Les différences de composition spécifique ont été évaluées par des tests de permutations multiples (Multi-Response Permutation Procédures; MRPP). Nous avons utilisé une analyse des espèces indicatrices (ISA) pour identifier les espèces caractéristiques des zones pâturées et non pâturées et des courbes rangs-abondances pour décrire les structures des communautés. Les différences de richesse en espèces, de hauteur et de biovolume des plantes ont été évaluées par des tests de Mann-Whitney. Les MRPP ont montré que les compositions des communautés pâturées, dominées par Puccinellia maritima et Festuca rubra ssp. litoralis, et non pâturées, dominées par Halimione portulacoides, diffèrent significativement (T = ―60,37; A = 0,10; p < 0,0001). Neuf espèces sont indicatrices des zones pâturées et quatre des zones non pâturées. Les communautés pâturées présentent une richesse spécifique plus élevée (3,5 ± 0,2 espèces.m-2) que celles non pâturées (2,9 ± 0,1 espèces.m-2; p < 0.001). Cette différence est notable dans des systèmes habituellement caractérisés par de faibles contrastes de richesse. Dans les relevés pâturés, la hauteur et le biovolume de végétation sont plus faibles et le recouvrement de la végétation plus élevé que dans les relevés non pâturés. Selon l'identité des espèces, les plantes perdent de 16,7 à 86,3% de leur hauteur sous pâturage ovin. Les espèces montrant la plus importante perte de hauteur (> 50%) sont principalement des halophytes pionnières et des Poacées. Aster tripolium, Suaeda maritima var. maritima, Halimione portulacoides, Spergularia marina sont particulièrement sensibles au pâturage et perdent plus de 90% de leur biovolume en présence des moutons. À travers des effets en cascade, le pâturage ovin réduit la hauteur de végétation, contrôle l'identité des espèces dominantes, limite les interactions compétitives pour la lumière entre espèces et, finalement, augmente la richesse spécifique. Nous recommandons donc un pâturage modéré et extensif pour la gestion des marais salés européens occupés par quelques espèces très dominantes. Finalement, nous avons classé les espèces selon leur degré d'abroutissement et leur valeur indicatrice de pâturage (ISA) pour fournir aux bergers un outil de terrain leur permettant d'évaluer l'impact des moutons sur les plantes des marais salés

Quantitative super-resolution imaging reveals protein stoichiometry and nanoscale morphology of assembling HIV-Gag virions

The HIV structural protein Gag assembles to form spherical particles of radius ∼70 nm. During the assembly process, the number of Gag proteins increases over several orders of magnitude from a few at nucleation to thousands at completion. The challenge in studying protein assembly lies in the fact that current methods such as standard fluorescence or electron microscopy techniques cannot access all stages of the assembly process in a cellular context. Here, we demonstrate an approach using super-resolution fluorescence imaging that permits quantitative morphological and molecular counting analysis over a wide range of protein cluster sizes. We applied this technique to the analysis of hundreds of HIV-Gag clusters at the cellular plasma membrane, thus elucidating how different fluorescent labels can change the assembly of virions

The social cognition of medical knowledge, with special reference to childhood epilepsy

This paper arose out of an engagement in medical communication courses at a Gulf university. It deploys a theoretical framework derived from a (critical) sociocognitive approach to discourse analysis in order to investigate three aspects of medical discourse relating to childhood epilepsy: the cognitive processes that are entailed in relating different types of medical knowledge to their communicative context; the types of medical knowledge that are constituted in the three different text types analysed; and the relationship between these different types of medical knowledge and the discursive features of each text type. The paper argues that there is a cognitive dimension to the human experience of understanding and talking about one specialized from of medical knowledge. It recommends that texts be studied in medical communication courses not just in terms of their discrete formal features but also critically, in terms of the knowledge which they produce, transmit and reproduce

High ecosystem service delivery potential of small woodlands in agricultural landscapes

Global forest loss and fragmentation have strongly increased the frequency of forest patches smaller than a few hectares. Little is known about the biodiversity and ecosystem service supply potential of such small woodlands in comparison to larger forests. As it is widely recognized that high biodiversity levels increase ecosystem functionality and the delivery of multiple ecosystem services, small, isolated woodlands are expected to have a lower potential for ecosystem service delivery than large forests hosting more species. We collected data on the diversity of six taxonomic groups covering invertebrates, plants and fungi, and on the supply potential of five ecosystem services and one disservice within 224 woodlands distributed across temperate Europe. We related their ability to simultaneously provide multiple ecosystem services (multiservice delivery potential) at different performance levels to biodiversity of all studied taxonomic groups (multidiversity), forest patch size and age, as well as habitat availability and connectivity within the landscape, while accounting for macroclimate, soil properties and forest structure. Unexpectedly, despite their lower multidiversity, smaller woodlands had the potential to deliver multiple services at higher performance levels per area than larger woodlands of similar age, probably due to positive edge effects on the supply potential of several ecosystem services. Biodiversity only affected multiservice delivery potential at a low performance level as well as some individual ecosystem services. The importance of other drivers of ecosystem service supply potential by small woodlands in agricultural landscapes also depended on the level of performance and varied with the individual ecosystem service considered. Synthesis and applications. Large, ancient woodlands host high levels of biodiversity and can therefore deliver a number of ecosystem services. In contrast, smaller woodlands in agricultural landscapes, especially ancient woodlands, have a higher potential to deliver multiple ecosystem services on a per area basis. Despite their important contribution to agricultural landscape multifunctionality, small woodlands are not currently considered by public policies. There is thus an urgent need for targeted policy instruments to ensure their adequate management and future conservation in order to either achieve multiservice delivery at high levels or to maximize the delivery of specific ecosystem services

High ecosystem service delivery potential of small woodlands in agricultural landscapes

Global forest loss and fragmentation have strongly increased the frequency of forest patches smaller than a few hectares. Little is known about the biodiversity and ecosystem service supply potential of such small woodlands in comparison to larger forests. As it is widely recognized that high biodiversity levels increase ecosystem functionality and the delivery of multiple ecosystem services, small, isolated woodlands are expected to have a lower potential for ecosystem service delivery than large forests hosting more species. We collected data on the diversity of six taxonomic groups covering invertebrates, plants and fungi, and on the supply potential of five ecosystem services and one disservice within 224 woodlands distributed across temperate Europe. We related their ability to simultaneously provide multiple ecosystem services (multiservice delivery potential) at different performance levels to biodiversity of all studied taxonomic groups (multidiversity), forest patch size and age, as well as habitat availability and connectivity within the landscape, while accounting for macroclimate, soil properties and forest structure. Unexpectedly, despite their lower multidiversity, smaller woodlands had the potential to deliver multiple services at higher performance levels per area than larger woodlands of similar age, probably due to positive edge effects on the supply potential of several ecosystem services. Biodiversity only affected multiservice delivery potential at a low performance level as well as some individual ecosystem services. The importance of other drivers of ecosystem service supply potential by small woodlands in agricultural landscapes also depended on the level of performance and varied with the individual ecosystem service considered. Synthesis and applications. Large, ancient woodlands host high levels of biodiversity and can therefore deliver a number of ecosystem services. In contrast, smaller woodlands in agricultural landscapes, especially ancient woodlands, have a higher potential to deliver multiple ecosystem services on a per area basis. Despite their important contribution to agricultural landscape multifunctionality, small woodlands are not currently considered by public policies. There is thus an urgent need for targeted policy instruments to ensure their adequate management and future conservation in order to either achieve multiservice delivery at high levels or to maximize the delivery of specific ecosystem services

The European Forest Plant Species List (EuForPlant): Concept and applications

Question When evaluating forests in terms of their biodiversity, distinctiveness and naturalness, the affinity of the constituent species to forests is a crucial parameter. Here we ask to what extent are vascular plant species associated with forests, and does species’ affinity to forests vary between European regions? Location Temperate and boreal forest biome of Northwestern and Central Europe. Methods We compiled EuForPlant, a new extensive list of forest vascular plant species in 24 regions spread across 13 European countries using vegetation databases and expert knowledge. Species were region-specifically classified into four categories reflecting the degree of their affinity to forest habitats: 1.1, species of forest interiors; 1.2, species of forest edges and forest openings; 2.1, species that can be found in forest as well as open vegetation; and 2.2, species that can be found partly in forest, but mainly in open vegetation. An additional “O” category was distinguished, covering species typical for non-forest vegetation. Results EuForPlant comprises 1,726 species, including 1,437 herb-layer species, 159 shrubs, 107 trees, 19 lianas and 4 epiphytic parasites. Across regions, generalist forest species (with 450 and 777 species classified as 2.1 and 2.2, respectively) significantly outnumbered specialist forest species (with 250 and 137 species classified as 1.1 and 1.2, respectively). Even though the degree of shifting between the categories of forest affinity among regions was relatively low (on average, 17.5%), about one-third of the forest species (especially 1.2 and 2.2) swapped categories in at least one of the study regions. Conclusions The proposed list can be used widely in vegetation science and global change ecology related to forest biodiversity and community dynamics. Shifting of forest affinity among regions emphasizes the importance of a continental-scale forest plant species list with regional specificity.publishedVersio

The European Forest Plant Species List (EuForPlant): Concept and applications

Question When evaluating forests in terms of their biodiversity, distinctiveness and naturalness, the affinity of the constituent species to forests is a crucial parameter. Here we ask to what extent are vascular plant species associated with forests, and does species' affinity to forests vary between European regions? Location Temperate and boreal forest biome of Northwestern and Central Europe. Methods We compiled EuForPlant, a new extensive list of forest vascular plant species in 24 regions spread across 13 European countries using vegetation databases and expert knowledge. Species were region-specifically classified into four categories reflecting the degree of their affinity to forest habitats: 1.1, species of forest interiors; 1.2, species of forest edges and forest openings; 2.1, species that can be found in forest as well as open vegetation; and 2.2, species that can be found partly in forest, but mainly in open vegetation. An additional "O" category was distinguished, covering species typical for non-forest vegetation. Results EuForPlant comprises 1,726 species, including 1,437 herb-layer species, 159 shrubs, 107 trees, 19 lianas and 4 epiphytic parasites. Across regions, generalist forest species (with 450 and 777 species classified as 2.1 and 2.2, respectively) significantly outnumbered specialist forest species (with 250 and 137 species classified as 1.1 and 1.2, respectively). Even though the degree of shifting between the categories of forest affinity among regions was relatively low (on average, 17.5%), about one-third of the forest species (especially 1.2 and 2.2) swapped categories in at least one of the study regions. Conclusions The proposed list can be used widely in vegetation science and global change ecology related to forest biodiversity and community dynamics. Shifting of forest affinity among regions emphasizes the importance of a continental-scale forest plant species list with regional specificity

Comparison of three seed trap types in a chalk grassland: toward a standardised protocol

In a chalk grassland in north-western France, vegetation and seed rain were studied along two transects. We compared the efficiency of three types of seed traps (funnel traps, sticky traps, pots exposed in the field) to estimate the annual seed rain and to reveal various processes involved in plant community regeneration. Data were analysed to compare seed density, species richness and composition across seed traps and vegetation. Geostatistical analyses (semivariograms. were used to detect possible autocorrelation and to examine patterns of spatial variation in seed rain and vegetation. The results show that (1) funnel traps are most efficient (56 species, 8079 seeds.m–2). (2) Each type of seed traps brings different information about the processes involved in seed dispersal and seedling establishment. Sticky traps help to understand import and export of seeds in a community through anemochory. Funnel traps may provide a measure of the auto-regeneration capacity of the vegetation through its local seed production. Pot traps integrate various processes involved between seed dispersal and seedling emergence. (3.) The exposition to environmental conditions generates marked spatial patterns in species richness measured in pots and in vegetation, selecting species able to survive. Pot traps indicate that numerous species producing seeds in standing vegetation are unable to establish in the field through seedling recruitment. Our study emphasizes the need of using different types of seed traps and spatial sampling configurations to assess the regenerative potential of standing vegetation and the various mechanisms involved in seed dispersal. A standardised protocol for seed rain sampling was finally develope