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article de 13 p.; International audience; Maintenance operations in regulated rivers are often implemented as preventive measure to maintain wide, smooth channels and to limit the risk of flooding. By clearing vegetation, removing roots and lowering sediment bar elevation, these works can recreate pioneer habitats and related plant communities. Using a before-after-control-impact design with monitoring of riparian vegetation over 10 years, we evaluated the effects of fluvial maintenance works on plant richness and composition in an island complex located in a Nature Reserve along the Middle Loire River. Our results showed that artificial rejuvenation operations had a significant short-term negative effect on richness. However, in the few years following the work, the riparian communities established on the rejuvenated island became more diverse, with a large proportion of annual plants, contributing to the increased species pool of the Nature Reserve. In addition, we found that temporal changes in species richness were strongly influenced by hydrological conditions, with a peak in biodiversity observed during prolonged summer low water. This highlights the importance of considering flow variations to more accurately assess the ecological benefit of restoration operations on riparian vegetation. Overall, as successional stages were more advanced at the island complex scale, fluvial maintenance works have allowed the recreation of sandy pioneer habitats exposed to flooding. These habitats have promoted the establishment of species-rich communities without favoring the installation of invasive alien species. From this view, the maintenance works have increased the mosaic of habitats within the Nature Reserve and have restored environmental conditions favorable to early-successional species.

International audience; Due to their particular topographic position between land and river, riparian forests are ecosystems rich in biodiversity. In France, along the Middle Loire (from Nevers to Angers), Black poplar (Populus nigra L.) forests are often in mixtures with the American maple (Acer negundo L.), introduced into the country in the 18th century. We tested the detectability of American maple by LiDAR and very high-resolution multispectral imagery on an island complex. We found that coupling the point cloud height standard deviation with a vegetation index in the red, green and blue spectrums discriminated American maple with a success rate of more than 90%.

Context: Forest ecosystems worldwide are facing increasing drought-induced dieback, causing mortality patches across the landscape at multiple scales. This increases the supply of biological legacies and differentially affects forest insect communities.Objectives: We analysed the relative effects of local- and landscape-level dieback on local saproxylic beetle assemblages. We assessed how classic concepts in spatial ecology (e.g. habitat-amount and habitat-patch hypotheses) are involved in relationships between multi-scale spatial patterns of available resources and local communities.Methods: We sampled saproxylic beetle assemblages in commercial fir forests in the French highlands. Through automatic aerial mapping, we used dead tree crowns to assess dieback levels at several nested spatial scales. We analysed beetle taxonomic, phylogenetic and functional diversity related to differing levels of multi-scale dieback.Results: In line with the habitat-amount hypothesis, taxonomic and functional diversity, but not phylogenetic diversity, of beetle assemblages significantly benefitted from forest dieback, at both local and landscape scales. Very few single or interaction effects were detected in the multiplicative models combining local and landscape variables, though a significant positive effect of landscape-scale dieback on the abundance of cavity- and fungus-dwelling species was consistent with a spill-over effect. Increased landscape-scale dieback also caused a functional specialisation of beetle assemblages, favouring those related to large-diameter, well-decayed deadwood.Conclusions: Increasing tree mortality under benign neglect provides conservation benefits by heterogenising the forest landscape and enhancing deadwood habitats. Legacy retention practices could take advantage of unharvested, declining forest stands to promote species richness and functional diversity within conventionally managed forest landscapes.

International audience; Aim Animal movement determines home range patterns, which in turn affect individual fitness, population dynamics and ecosystem functioning. Using temperate bats, a group of particular conservation concern, we investigated how morphological traits, habitat specialization and environmental variables affect home range sizes and daily foraging movements, using a compilation of 30 years of published bat telemetry data. Location Northern America and Europe. Time period 1988-2016. Major taxa studied Bats. Methods We compiled data on home range size and mean daily distance between roosts and foraging areas at both colony and individual levels from 166 studies of 3,129 radiotracked individuals of 49 bat species. We calculated multi-scale habitat composition and configuration in the surrounding landscapes of the 165 studied roosts. Using mixed models, we examined the effects of habitat availability and spatial arrangement on bat movements, while accounting for body mass, aspect ratio, wing loading and habitat specialization. Results We found a significant effect of landscape composition on home range size and mean daily distance at both colony and individual levels. On average, home ranges were up to 42% smaller in the most habitat-diversified landscapes while mean daily distances were up to 30% shorter in the most forested landscapes. Bat home range size significantly increased with body mass, wing aspect ratio and wing loading, and decreased with habitat specialization. Main conclusions Promoting bat movements through the landscape surrounding roosts at large spatial scales is crucial for bat conservation. Forest loss and overall landscape homogenization lead temperate bats to fly further to meet their ecological requirements, by increasing home range sizes and daily foraging distances. Both processes might be more detrimental for smaller, habitat-specialized bats, less able to travel increasingly longer distances to meet their diverse needs.

Menée au sein de la réserve naturelle nationale (RNN) de Saint-Mesmin (45), sur la Loire, en périphérie aval de la ville d’Orléans, cette étude compare la biodiversité floristique de la ripisylve d’une berge à celle de deux îles boisées en vis-à-vis. L’hypothèse est que la berge, davantage soumise à la pression anthropique, présente une biodiversité altérée. Les relevés floristiques ont été effectués à l’échelle de l’écocomplexe (environ deux hectares par entité), en trois passages annuels et pendant quatre années (2013 à 2016). La berge et chaque île ont une richesse totale similaire, d’environ 310 espèces, et présentent des différences de composition modérées. La principale différence concerne une plus forte présence des espèces oligotrophiles, localisées aux grèves et pelouses des îles, alors que les espèces eutrophiles sont favorisées sur la berge. Si les espèces patrimoniales, toujours en faible effectif, ont tendance à être plus nombreuses sur les îles, la berge en accueille aussi de façon complémentaire. Les espèces exogènes ne sont pas plus nombreuses sur la berge que sur les îles alors que les espèces invasives sont plus abondantes sur les îles. Au final, les ripisylves de berge présentent une flore aussi intéressante que celle des îles, leur composition est complémentaire au bénéfice de la biodiversité de la RNN. Les berges boisées méritent d’être gérées avec attention du fait de leur forte exposition à la fréquentation humaine dans ce contexte péri-urbain, ce qui demande notamment de sensibiliser les promeneurs à leur fragilité. Si cette étude de cas est utile pour la gestion de la RNN, la généralisation des résultats nécessiterait l’examen préalable d’autres couples berge/île le long de la Loire.

Questions How did past land use and conifer plantation affect understorey plant communities? What plant traits explain understorey vegetation response to agricultural past land use and coniferous plantation? Location Forest of Orleans (50 000 ha), Loiret, north-central France. Methods Canopy cover, herb layer composition, litter and soil properties were measured in 80 100 m2 plots sampled in plantations of Pinus sylvestris or P. nigra vs natural regenerations of Quercus petraea and Q. robur along a gradient of forest continuity (using historical maps and aerial photos from 1840, 1949 and 2006). We related 15 plant traits to past land use and tree species using RLQ and fourth-corner analyses. Results The magnitude of past land use effect largely exceeded that of coniferous plantation. Post-agricultural forests, even 150 yr after afforestation, differed from ancient forests in soil properties (thinner humus layer, higher P content, higher pH and lower C/N ratio) and plant traits. Ancient forests hosted more forest core species, stress-tolerant, competitive species and bryophytes, but fewer ruderals, annuals/biennials, shrubs and trees and nutrient-demanding species, and had lower SLA and higher LDMC. Conifer plantations had a thicker humus layer, lower pH and higher C/N ratio than deciduous forests, and hosted more light-demanding species but less forest core species. Importantly, differences in soil and plant traits between conifer plantations and naturally regenerated deciduous stands were discernible in both recent and ancient forests, indicating that tree species lastingly influence ecosystem functioning. Conclusions Past land use and coniferous plantation resulted in different understorey plant communities and traits under pine plantations and naturally regenerated oak stands. These differences were driven through soil acidification, litter decomposition rate, light conditions, canopy development, soil disturbance, stand management and dispersal and recruitment limitations. Coniferous plantations slowed down the recovery of post-agricultural forests to ancient deciduous forest conditions. Applying natural regeneration and favouring native deciduous tree species thus helps recreate or maintain ancient forest plant communities.

Ce projet de recherche a étudié les conséquences des travaux d’entretien du lit de la Loire sur plusieurs composantes de la biodiversité (faune et flore) au sein de la mosaïque d’ilots de 13 hectares de Mareau-aux-Prés (inclus dans la Réserve Naturelle Nationale de St-Mesmin, Loiret). Suite aux travaux (dévégétalisation et reprofilage), un nouvel assemblage de communautés s’est mis progressivement en place. Ce projet est centré sur cette nouvelle dynamique de recolonisation: la biodiversité intra et interspécifique a été étudiée pendant 3 ans avant et après travaux (via l’acquisition de données in situ et d’analyses génétiques et spatialisées) autour de quatre compartiments biologiques : (1) végétation herbacée, arbustive et arborescente, autochtone et exotique (2) entomofaune coléoptère Carabidae (3) avifaune nicheuse des grèves (4) castor d’Europe. Nous avons pu observer et mesurer une succession quasi primaire alimentée par le flux de populations provenant des autres ilots, îles et berges., This research project studied the impact of fluvial maintenance works (FMW) on several biodiversity components (fauna and flora) within the island mosaic of Mareau-aux-Prés on the Loire river (within the St-Mesmin National Nature Reserve, Loiret). Following the FMW (vegetation uprooted and bar lowered), a new set of communities have gradually established on the island. This project focuses on the dynamic of recolonization: intra- and interspecific biodiversity has been studied for 3 years before and after FMW (via in situ data and spatial and genetic analysis) on four biological compartments (1) herbaceous plants, shrubs and trees, native and exotic (2) ground beetles Carabidae (3) gravel nesting birds (4) beaver (Castor fiber).

International audience; Linear elements: - Not sufficient to preserve butterfly communities Woodlands: - Positive effect even on grassland specialists Species of conservation concern most impacted: - Homogenization of communities Connectivity metrics: - Using multiple metrics help to understand population/community functioning

International audience; In agricultural landscapes, permanent grassy habitats are often fragmented and partly composed of linear elements. Landscape-level connectivity of both grassland patches and grassy linear elements actively contributes to biodiversity conservation in farmland. Nevertheless, their respective importance has rarely been tested. Butterflies form a suitable model group for this purpose; they have suffered a major overall decline in the last few decades and are known to be sensitive to landscape connectivity. We sampled 286 transects nested in 18 study landscapes in three regions. Using several metrics, we analyzed the response of butterflies to the connectivity to both grassland and woodland habitats, which may provide additional resources. The response to landscape connectivity appeared to depend on the type of the semi-natural elements (patch vs linear elements), and on species traits, i.e. the response was stronger for habitat specialists and species with low dispersal ability. We found that woody habitats close to grassland patches had a significant positive effect on butterfly communities, denoting potential mechanisms of resources supplementation and complementation. In grassy linear elements, butterfly communities were of lower conservation value, richness and abundance were much lower (- 26 and - 50%) than in grassland patches and decreased with isolation from grasslands, in line with the source–sink hypothesis. Although grassy linear elements probably play an important role in butterfly dispersal in agricultural landscapes, they may not be sufficient to preserve specialist and sedentary species. Conserving a mosaic of high quality grassland patches and woody habitats appears more effective than enhancing connectivity.

Weakly electric fish continuously emit a quasi-sinusoidal electric organ discharge (EOD) to probe their near environment (electrolocation). P-type tuberous receptors located on their skin respond to the periodic EOD by triggering action potentials in a phase locked manner. It is observed that the intervals between firing times are random multiples of the EOD period. This is known as skipping. Weak carrier amplitude modulations caused by relevant stimuli are encoded by P-type receptors through modulation of their output firing rate. We investigate the effect of P---the baseline firing probability per EOD cycle of a receptor---as well as of other parameters on the quality of information transfer in four biophysically plausible numerical receptor models. In particular, we study how internal noise affects the transduction of random EOD modulations, since noise is perhaps essential for good neural computation. Information is quantified using the stimulus reconstruction technique. We discuss the firing characteristics of the four considered models and discuss their relevance as models of P-afferents. Our information measurements indicate that the presence of noise may enhance information transfer in these receptors. And the coding quality is found to not depend on P alone, but also on the actual combination of biophysical parameters that determine P.

Les plantations de peuplier hybride augmentent en surface dans le monde entier et elles sont souvent accusées d'appauvrir les communautés d'oiseaux. Nous avons réalisé 124 points d'écoute dans un paysage où les plantations, les forêts semi-naturelles et les milieux agricoles représentent des surfaces similaires. Comme attendu,les densités des oiseaux étaient plus fortes dans les secteurs dominés par la forêt que dans ceux dominés par les plantations, essentiellement du fait de la rareté des espèces des vieux stades forestiers dans les plantations. Contrairement à nos attentes, les communautés étaient les plus appauvries dans les secteurs agricoles et les plus spécialisées dans les secteurs dominés par les jeunes plantations. En effet, un certain nombre d'espèces des prairies, certaines au statut de conservation défavorable en Europe, ont été observées dans ces plantations. Néanmoins, les plantations ont probablement participé à la rareté de ces espèces à l'échelle du paysage en fragmentant les espaces ouverts, tout en jouant un rôle positif limité de reconnection des éléments boisés persitants. La longueur cumulée des chemins autour du point d'écoute influençait positivement les espèces spécialistes, tandis que la longueur cumulée de routes pavées et la taille moyenne des plantations et boisements ne jouaient pas de rôle. La densité augmentait avec le développement du sous-étage dans les plantations mature. Nous concluons que le peuplier ne doit pas être planté au détriment de zones de forte valeur patrimoniale; dans les autres cas, ces plantations peuvent accroître la diversité globale des communautés d'oiseaux. A l'échelle de la plantation, nous recommandons d'arrêter le contrôle de la végétation herbacée et arbustive dès que ces strates ne menacent plus la croissance de la plantation, et de maintenir de vieux arbres et des haies au sein ou le long des plantations pour les espèces susceptibles de nicher ou de se nourrir dans les plantations. / Hybrid poplar plantations are increasing worldwide and are often accused of impoverishing bird communities. We conducted 124 bird point counts in a landscape where plantations, semi-natural forests and farmland occupied similar surface areas. As expected, birds occurred at higher densities in areas dominated by forests than dominated by plantations, mostly due to the scarcity of latesuccessional forest birds in plantations. Contrary to expectations, bird communities were the poorest in farmland dominated areas and the most specialised in areas dominated by young plantations. Indeed, many grassland species, including some of conservation concern in Europe, frequently used young plantations. However, plantations have probably depleted grassland bird communities by fragmenting open areas, while playing a limited positive role on forest species. Total length of unpaved roads had a positive effect on community specialisation index, while total length of paved roads and mean forest/plantation patch size played no role. Bird density increased with the development of the understory vegetation in mature poplar plantations. We conclude that poplar should not be planted at the expense of areas of high conservation value; in other cases, they may increase the overall diversity of bird communities. At the plantation scale, we advocate stopping understory removal as soon as possible and maintaining old trees and hedgerows alongside or within plantations to provide suitable breeding habitats for bird species that may be foraging in the plantations.

This report shows the work done in 2014 by Irstea, INRA, ONF and CNPF in the framework of a research programme dedicated to improved varieties testing. It includes six species: Douglas-fir, larch, Norway spruce, black pine, wild cherry and ash. With regard to Douglas-fir, the results concern i) survival, health and height growth of French varieties (measurements done in 8 trials included in a recent network of comparative trials that aims to compare the eight French seed orchards), ii) actions undertaken to broaden this network, iii) cold hardiness, iv) resistance to drought (cavitation) and v) lateness of flushing of progenies produced by the clones of a French seed orchard (Californie). Results related to larch mainly concern the modulus of elasticity of hybrid and non-hybrid progenies produced in five European hybridisation orchards., Ce rapport présente les actions entreprises en 2014 par Irstea, l'INRA, l'ONF et le CNPF dans le cadre de l'évaluation des variétés issues des vergers à graines de l'Etat. Elles concernent 6 espèces : Douglas, mélèzes, épicéa commun, pins laricio, merisier et frêne. Pour ce qui concerne le Douglas, les résultats concernent i) la survie, l’état sanitaire et la croissance en hauteur des 8 variétés françaises (mesures effectuées dans 8 dispositifs du réseau d’évaluation national) ii) les actions entreprises pour étendre ce réseau, iii) l’acclimatation au froid, iv) la résistance à la sécheresse (résistance à la cavitation) et v) la tardiveté de débourrement des descendances du verger « Californie » utilisable en zone méditerranéenne. Les actions liées aux mélèzes concernent principalement des mesures de module d’élasticité sur des descendances hybrides et non hybrides de 5 vergers d’hybridation européens.

National audience; This research project studied the impact of fluvial maintenance works (FMW) on several biodiversity components (fauna and flora) within the island mosaic of Mareau-aux-Prés on the Loire river (within the St-Mesmin National Nature Reserve, Loiret). Following the FMW (vegetation uprooted and bar lowered), a new set of communities have gradually established on the island. This project focuses on the dynamic of recolonization: intra- and interspecific biodiversity has been studied for 3 years before and after FMW (via in situ data and spatial and genetic analysis) on four biological compartments (1) herbaceous plants, shrubs and trees, native and exotic (2) ground beetles Carabidae (3) gravel nesting birds (4) beaver (Castor fiber).; Ce projet de recherche a étudié les conséquences des travaux d’entretien du lit de la Loire sur plusieurs composantes de la biodiversité (faune et flore) au sein de la mosaïque d’ilots de 13 hectares de Mareau-aux-Prés (inclus dans la Réserve Naturelle Nationale de St-Mesmin, Loiret). Suite aux travaux (dévégétalisation et reprofilage), un nouvel assemblage de communautés s’est mis progressivement en place. Ce projet est centré sur cette nouvelle dynamique de recolonisation: la biodiversité intra et interspécifique a été étudiée pendant 3 ans avant et après travaux (via l’acquisition de données in situ et d’analyses génétiques et spatialisées) autour de quatre compartiments biologiques : (1) végétation herbacée, arbustive et arborescente, autochtone et exotique (2) entomofaune coléoptère Carabidae (3) avifaune nicheuse des grèves (4) castor d’Europe. Nous avons pu observer et mesurer une succession quasi primaire alimentée par le flux de populations provenant des autres ilots, îles et berges.

Master; Wild ungulate populations (cervidae and wild boar Sus Scrofa) have dramatically increased in North America and Western Europe during the past century. Their strong interactions with forest ecosystem are notably known to impact negatively woodland bird communities. In this study we investigated the potential effects of ungulate density on nest predation of low-nesting birds and bird communities in forest ecosystems. In order to test this impact, 528 artificial nests monitored with camera traps were set both in fenced plots excluding ungulates and in unfenced plots. We used (generalized) linear mixed models to explain (1) impact of ungulates on predation, on other potential predators and on bird communities, and (2) to know which variables explained spatio-temporal variation in nest predation rate among those related to plot type (fenced/unfenced), ungulates and other egg predators, bird communities and plot vegetal features. Our study failed to demonstrate a noticeable egg predation effect of deer and even wild boar, as well as any attractive effect on alternative avian or mammalian predators. Yet ungulates browsing of low vegetation may facilitate the detection of nests in these layers by these predators. Finally, bird communities are influenced by neither local abundance of predators, nor those of ungulates.