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Dans le contexte de changement climatique, la variation spatio-temporelle des paramètres climatiques entraîne de sérieux problèmes au développement du secteur touristique. Il s’agit notamment des problèmes de déplacements, de planification des activités, de choix des destinations, d’aménagement des infrastructures touristiques et des sites. La présente étude a pour objectif d’analyser l’impact des paramètres climatiques sur le secteur du tourisme à Laongo (Burkina Faso). Les résultats de l’étude montrent que le tourisme subit à court et long termes l’impact des paramètres climatiques. À court terme, ce sont les activités touristiques et la fréquentation du site qui sont affectées. Les températures élevées, la pluviométrie, les vents poussiéreux rendent désagréables les activités touristiques ; les précipitations jouent sur leurs planifications : en cas de pluie, les activités sont annulées, ou reportées selon sa durée. En outre, les températures élevées, et les précipitations ralentissement ou réduisent la fréquentation du site.À long terme, les paramètres climatiques contribuent à la dégradation physique et à l’altération chimique des œuvres qui y sont exposées en plein air. La détérioration physique est due à la variation des températures (thermoclastie), à l’action des vents par les particules transportées, et à l’action de la pluie (effet splash). L’altération chimique est due à l’action des eaux de pluie, qui agissent soit seule, par le mécanisme de l’hydrolyse, soit en combinaison avec le CO2 et l’air, par les mécanismes de dissolution et d’oxydation.L’étude a en outre révélé que les paramètres climatiques ne sont pas les seuls responsables de l’altération des œuvres. Les êtres vivants, tels que l’homme et les mousses, sont aussi des vecteurs de dégradation. L’homme agit par le toucher, et les mousses par leur composition chimique et leurs racines. À partir de ce constat, des stratégies doivent être développées, pour protéger les œuvres de l’attaque des facteurs climatiques, de l’action des êtres vivants, afin de rendre attractive et durable l’organisation des activités touristiques durant les périodes de fortes chaleurs, de pluies, et de vents porteurs de poussières. In the context of climate change, the spatiotemporal variation of climatic parameters causes serious problems for the development of the tourism sector. These include issues of travel, planning of activities, choice of destinations, development of tourist infrastructure and sites.The objective of this study is to analyze the impact of climatic parameters on the tourism sector in Laongo (Burkina Faso). The results of the study show that tourism is affected in the short and long term by climatic parameters.In the short term, it is tourist activities and frequentation of the site that are influenced. The high temperatures, the pluviometry, the dusty winds, make tourist activities unpleasant; precipitation affects their planning: in the event of rain, activities are cancelled or postponed depending on its duration. In addition, high temperatures, and precipitation slowing or reducing site attendance.In the long term, climatic parameters contribute to the physical degradation and chemical alteration of the works exhibited there in the open air. The physical deterioration is due to the variation of temperatures (thermoclasty), to the action of the winds by the transported particles, and to the action of the rain (splash effect). Chemical weathering is due to the action of rainwater, which acts either alone, by the mechanism of hydrolysis, or in combination with CO2 and air, by the mechanisms of dissolution and oxidation.The study further revealed that climatic parameters are not the only ones responsible for the alteration of the works. Living things, such as humans and mosses, are also factors of degradation. Man acts by touch, and mosses by their mineralogical composition and their roots.From this observation, strategies must be developed to protect the works from attack by climatic factors, from the action of living beings, in order to make the organization of tourist activities pleasant and sustainable during periods of strong heat, rains, and dusty winds. En el contexto del cambio climático, la variación espacio-temporal de los parámetros climáticos genera serios problemas para el desarrollo del sector turístico. Estos incluyen cuestiones de viajes, planificación de actividades, elección de destinos, desarrollo de infra-estructura y sitios turísticos.El objetivo de este estudio es analizar el impacto de los parámetros climáticos en el sector turístico de Laongo (Burkina Faso). Los resultados del estudio muestran que el turismo se ve afectado a corto y largo plazo por los parámetros climáticos.En el corto plazo, son las actividades turísticas y la frecuentación del sitio las que se ven influenciadas. Las altas temperaturas, las lluvias, los vientos polvorientos, hacen incómodas las actividades turísticas; las precipitaciones afectan su planificación: en caso de lluvia, las actividades se cancelan o posponen en función de su duración. Además, las altas temperaturas y las precipitaciones ralentizan o reducen la asistencia al sitio.A largo plazo, los parámetros climáticos contribuyen a la degradación física y alteración química de las obras allí expuestas al aire libre. El deterioro físico se debe a la variación de temperaturas (termoclastia), a la acción de los vientos por las partículas transportadas y a la acción de la lluvia (efecto salpicadura). La meteorización química se debe a la acción del agua de lluvia, que actúa sola, por el mecanismo de hidrólisis, o en combinación con el CO2 y el aire, por los mecanismos de disolución y oxidación.El estudio reveló además que los parámetros climáticos no son los únicos responsables del deterioro de las obras. Los seres vivos, como los humanos y los musgos, también son factores de degradación. El hombre actúa por el tacto y los musgos por su composición mineralógica y sus raíces.A partir de esta observación, se deben desarrollar estrategias para proteger las obras del ataque de los factores climáticos, de la acción de los seres vivos, con el fin de hacer que la organización de las actividades turísticas sea placentera y sostenible durante los períodos de fuerte calor, lluvias y vientos polvorientos.

We thank the staff of the INRAE Experimental facilities of the Plant Pathology research unit (IEPV, https://doi.org/10.15454/8DGF-QF70) for their involvement in field experiments; International audience; Microbial aerosols (mainly composed by bacterial and fungal cells), may constitute up to 74 % of the total aerosol volume. These biological aerosols are relevant not only from the point of view of the dispersion of pathogenic species, but also due to the potential geochemical implications. Some bacteria and fungi may, in fact, serve as cloud condensation or ice nuclei, potentially affecting cloud formation and precipitation and are active at higher temperatures compared to their, much more intensively studied, inorganic counterparts. Simulations of the impact of microbial aerosols on climate are still hindered by the lack of information regarding their emissions from ground sources. This work tackles this knowledge gap by (i) applying a rigorous micrometeorological approach to the estimation of microbial net fluxes above a Mediterranean grassland and (ii) developing a deterministic model to estimate these emissions on the basis of a few easily recovered meteorological parameters (the PLAnET model). The grassland itself is characterized by an abundance of positive net microbial fluxes and the model proves to be a promising tool capable of capturing the day-to-day variability in microbial fluxes with a relatively small bias and sufficient accuracy. PLAnET is still in its infancy and will benefit from future campaigns extending the available training dataset as well as the inclusion of ever more complex and critical phenomena affecting the release of microbial aerosol (such as rainfall). The model itself is also adaptable as an emission module for dispersion and chemical transport models, allowing to further explore the impact of microbial aerosols on the atmosphere and climate.

International audience; In the subalpine forest ecosystems of the French Alps, European larch trees (Larix decidua Mill.) are periodically affected by outbreaks of a defoliating insect, the larch budmoth (Zeiraphera griseana (Hubner, 1799); LBM). To assess the long-term dynamics of LBM populations, we propose a spatiotemporal analysis of a long outbreak chronology reconstruction for the entire French Alps covering the period 1414-2009. This chronology was obtained by analyzing tree ring width (TRW) chronologies collected from 44 larch populations. The evidence of a latitudinal gradient in LBM is an original result that we have related to the "travelling waves" and "epicenter" theory. Wavelet analyses revealed a strong explicit continuous signal for periodicities of 4, 8, and 16 years throughout the entire 1500-2003 time series, except for a loss of power from 1690 to 1790 and since the early 1980s. We hypothesize that these abrupt changes could reflect a physiological response of LBM to past climatic variations. The spatial and temporal variability of LBM outbreaks and the propagation phenomenon in the French Alps highlighted by this study raises questions regarding its future dynamics in response to the expected climate change.; Dans les écosystèmes forestiers subalpins des Alpes françaises, le mélèze (Larix decidua Mill.) subit périodiquement les épidémies d’un insecte défoliateur, la tordeuse du mélèze (Zeiraphera griseana (Hübner, 1799); LBM). Afin de mieux comprendre les dynamiques à long terme des populations de tordeuse, nous proposons dans cet article une analyse spatio-temporelle d’une très longue reconstruction des épidémies pour la période 1414–2009 sur l’ensemble des Alpes françaises. Cette chronologie a pu être reconstruite à partir des cernes de croissance de 44 populations de mélèze. Les résultats ont permis de mettre en évidence le rôle d’un gradient latitudinal que nous avons attribué au phénomène théorique des « épicentres » et « vagues de dissémination ». D’autre part, les analyses temporelles, réalisées à l’aide de la méthode des ondelettes, ont révélé l’existence d’un fort signal continu pour des fréquences périodiques de 4, 8 et 16 ans sur l’ensemble de la chronologie à l’exception d’une perte d’énergie entre 1690 et 1790 et depuis le début des années 1980. Ces changements pourraient refléter une réponse physiologique de la tordeuse à des variations climatiques passées. La variabilité temporelle et spatiale des épidémies de tordeuse ainsi que le mode de propagation à travers les Alpes françaises nous ont conduits à nous interroger sur les dynamiques futures de l’insecte et de son hôte en réponse au réchauffement climatique rapide dans les écosystèmes de haute élévation.

Some biological particles and macromolecules are particularly efficient ice nuclei (IN), triggering ice formation at temperatures close to 0 ∘C. The impact of biological particles on cloud glaciation and the formation of precipitation is still poorly understood and constitutes a large gap in the scientific understanding of the interactions and coevolution of life and climate. Ice nucleation activity in fungi was first discovered in the cosmopolitan genus Fusarium, which is widespread in soil and plants, has been found in atmospheric aerosol and cloud water samples, and can be regarded as the best studied ice-nucleation-active (IN-active) fungus. The frequency and distribution of ice nucleation activity within Fusarium, however, remains elusive. Here, we tested more than 100 strains from 65 different Fusarium species for ice nucleation activity. In total, ∼11 % of all tested species included IN-active strains, and ∼16 % of all tested strains showed ice nucleation activity above −12 ∘C. Besides Fusarium species with known ice nucleation activity, F. armeniacum, F. begoniae, F. concentricum, and F. langsethiae were newly identified as IN-active. The cumulative number of IN per gram of mycelium for all tested Fusarium species was comparable to other biological IN like Sarocladium implicatum, Mortierella alpina, and Snomax®. Filtration experiments indicate that cell-free ice-nucleating macromolecules (INMs) from Fusarium are smaller than 100 kDa and that molecular aggregates can be formed in solution. Long-term storage and freeze–thaw cycle experiments revealed that the fungal IN in aqueous solution remain active over several months and in the course of repeated freezing and thawing. Exposure to ozone and nitrogen dioxide at atmospherically relevant concentration levels also did not affect the ice nucleation activity. Heat treatments at 40 to 98 ∘C, however, strongly reduced the observed IN concentrations, confirming earlier hypotheses that the INM in Fusarium largely consists of a proteinaceous compound. The frequency and the wide distribution of ice nucleation activity within the genus Fusarium, combined with the stability of the IN under atmospherically relevant conditions, suggest a larger implication of fungal IN on Earth’s water cycle and climate than previously assumed.

Partie 3 : Douglas-fir ecology; International audience

International audience; The Tambora eruption (1815 AD) was one of the major eruptions of the last two millennia and has noequivalents over the last two centuries. Here, we collected an extensive network of earlymeteorological time series, climate simulation data and numerous, well-replicated proxy records from Eastern Canada to analyze the strength and the persistence of the Tambora impact on the regional climate and forest processes. Our results show that the Tambora impacts on the terrestrial biosphere were stronger than previously thought, and not only affected tree growth and carbon uptake for a longer period than registered in the regional climate, but also determined forest demography and structure. Increased tree mortality, four times higher than the background level, indicates that the Tambora climatic impact propagated to influence the structure of the North American taiga for several decades.We also show that the Tambora signal is more persistent in observed data (temperature, river ice dynamics, forest growth, tree mortality) than in simulated ones (climate and forest-growth simulations), indicating that our understanding of the mechanisms amplifying volcanic perturbations on climates and ecosystems is still limited, notably in the North American taiga.

Many microbes relevant to crops, domestic animals, and humans are transported over long distances through the atmosphere. Some of these atmospheric microbes catalyze the freezing of water at higher temperatures and facilitate the onset of precipitation. We collected microbes from the lower atmosphere in France and the United States with a small unmanned aircraft system (sUAS). 55 sampling missions were conducted at two locations in France in 2014 (an airfield in Pujaut, and the top of Puy de Dôme), and three locations in the U.S. in 2015 (a farm in Blacksburg, Virginia, and a farm and a lake in Baton Rouge, Louisiana). The sUAS was a fixed-wing electric drone equipped with a remote-operated sampling device that was opened once the aircraft reached the desired sampling altitude (40–50 meters above ground level). Samples were collected on agar media (TSA, R4A, R2A, and CA) with and without the fungicide cycloheximide. Over 4,000 bacterial-like colonies were recovered across the 55 sUAS sampling missions. A positive relationship between sampling time and temperature and concentrations of culturable bacteria was observed for sUAS flights conducted in France, but not for sUAS flights conducted in Louisiana. A droplet freezing assay was used to screen nearly 2,000 colonies for ice nucleation activity, and 15 colonies were ice nucleation active at temperatures warmer than −8°C. Sequences from portions of 16S rDNA were used to identify 503 colonies from 54 flights to the level of genus. Assemblages of bacteria from sUAS flights in France (TSA) and sUAS flights in Louisiana (R4A) showed more similarity within locations than between locations. Bacteria collected with sUAS on TSA in France and Virginia were significantly different across all levels of classification tested (P < 0.001 for class, order, family, and genus). Principal Coordinates Analysis showed a strong association between the genera Curtobacterium, Pantoea, and Pseudomonas from sUAS flights in Virginia, and Agrococcus, Lysinibacillus, and Paenibacillus from sUAS flights in France. Future work aims to understand the potential origin of the atmospheric microbial assemblages collected with sUAS, and their association with mesoscale atmospheric processes.

Prolonged diapause occurs in a number of insects and is interpreted as a way to evade adverse conditions. The winter pine processionary moths (Thaumetopoea pityocampa and Th. wilkinsoni) are important pests of pines and cedars in the Mediterranean region. They are typically univoltine, with larvae feeding across the winter, pupating in spring in the soil and emerging as adults in summer. Pupae may, however, enter a prolonged diapause with adults emerging one or more years later. We tested the effect of variation in winter temperature on the incidence of prolonged diapause, using a total of 64 individual datasets related to insect cohorts over the period 1964 2015 for 36 sites in seven countries, covering most of the geographic range of both species. We found high variation in prolonged diapause incidence over their ranges. At both lower and upper ends of the thermal range in winter, prolonged diapause tended to be higher than at intermediate temperatures. Prolonged diapause may represent a risk-spreading strategy to mitigate climate uncertainty, although it may increase individual mortality because of a longer exposure to mortality factors such as predation, parasitism, diseases or energy depletion. Climate change, and in particular the increase of winter temperature, may reduce the incidence of prolonged diapause in colder regions whereas it may increase it in warmer ones, with consequences for population dynamics., Work supported by Fondazione Cassa di Risparmio di Padova e Rovigo to Md H.R. Salman, University of Padova to Myron P. Zalucki and Folco Giomi, Spanish Ministry of the Environment (PROPINOL PN22/2008 and CONSOLIDER-MONTES CSD2008- 00040) to José A. Hodar, DIAMETABO project of the INRA EFPA department to Mathieu Laparie, European Union's Horizon 2020 research and innovation programme under grant agreement N. 771271 HOMED (Holistic Management of Emerging forest pests and Diseases) to Andrea Battisti.

Microbial aerosols (mainly composed of bacterial and fungal cells) may constitute up to 74 % of the total aerosol volume. These biological aerosols are not only relevant to the dispersion of pathogens, but they also have geochemical implications. Some bacteria and fungi may, in fact, serve as cloud condensation or ice nuclei, potentially affecting cloud formation and precipitation and are active at higher temperatures compared to their inorganic counterparts. Simulations of the impact of microbial aerosols on climate are still hindered by the lack of information regarding their emissions from ground sources. This present work tackles this knowledge gap by (i) applying a rigorous micrometeorological approach to the estimation of microbial net fluxes above a Mediterranean grassland and (ii) developing a deterministic model (the PLAnET model) to estimate these emissions on the basis of a few meteorological parameters that are easy to obtain. The grassland is characterized by an abundance of positive net microbial fluxes and the model proves to be a promising tool capable of capturing the day-to-day variability in microbial fluxes with a relatively small bias and sufficient accuracy. PLAnET is still in its infancy and will benefit from future campaigns extending the available training dataset as well as the inclusion of ever more complex and critical phenomena triggering the emission of microbial aerosol (such as rainfall). The model itself is also adaptable as an emission module for dispersion and chemical transport models, allowing further exploration of the impact of land-cover-driven microbial aerosols on the atmosphere and climate.

© 2017 The Author(s) Forest-driven water and energy cycles are poorly integrated into regional, national, continental and global decision-making on climate change adaptation, mitigation, land use and water management. This constrains humanity's ability to protect our planet's climate and life-sustaining functions. The substantial body of research we review reveals that forest, water and energy interactions provide the foundations for carbon storage, for cooling terrestrial surfaces and for distributing water resources. Forests and trees must be recognized as prime regulators within the water, energy and carbon cycles. If these functions are ignored, planners will be unable to assess, adapt to or mitigate the impacts of changing land cover and climate. Our call to action targets a reversal of paradigms, from a carbon-centric model to one that treats the hydrologic and climate-cooling effects of trees and forests as the first order of priority. For reasons of sustainability, carbon storage must remain a secondary, though valuable, by-product. The effects of tree cover on climate at local, regional and continental scales offer benefits that demand wider recognition. The forest- and tree-centered research insights we review and analyze provide a knowledge-base for improving plans, policies and actions. Our understanding of how trees and forests influence water, energy and carbon cycles has important implications, both for the structure of planning, management and governance institutions, as well as for how trees and forests might be used to improve sustainability, adaptation and mitigation efforts. publisher: Elsevier articletitle: Trees, forests and water: Cool insights for a hot world journaltitle: Global Environmental Change articlelink: http://dx.doi.org/10.1016/j.gloenvcha.2017.01.002 content_type: article copyright: © 2017 The Author(s). Published by Elsevier Ltd. ispartof: Global Environmental Change vol:43 pages:51-61 status: published

Microbial aerosols (mainly composed by bacterial and fungal cells), may constitute up to 74 % of the total aerosol volume. These biological aerosols are relevant not only from the point of view of the dispersion of pathogenic species, but also due to the potential geochemical implications. Some bacteria and fungi may, in fact, serve as cloud condensation or ice nuclei, potentially affecting cloud formation and precipitation and are active at higher temperatures compared to their, much more intensively studied, inorganic counterparts. Simulations of the impact of microbial aerosols on climate are still hindered by the lack of information regarding their emissions from ground sources. This work tackles this knowledge gap by (i) applying a rigorous micrometeorological approach to the estimation of microbial net fluxes above a Mediterranean grassland and (ii) developing a deterministic model to estimate these emissions on the basis of a few easily recovered meteorological parameters (the PLAnET model). The grassland itself is characterized by an abundance of positive net microbial fluxes and the model proves to be a promising tool capable of capturing the day-to-day variability in microbial fluxes with a relatively small bias and sufficient accuracy. PLAnET is still in its infancy and will benefit from future campaigns extending the available training dataset as well as the inclusion of ever more complex and critical phenomena affecting the release of microbial aerosol (such as rainfall). The model itself is also adaptable as an emission module for dispersion and chemical transport models, allowing to further explore the impact of microbial aerosols on the atmosphere and climate.

International audience

Earth has recently entered the new era of the Anthropocene, during which the rise of human activities are impacting for the first time ecosystems and climate on the global scale. Since the 1960s the green revolution has improved food production in quantity using industrially-designed agriculture, which has led to global pollution by pesticides and losses of food quality, biodiversity and soil carbon. As a consequence there is a need to implement agroecological practices in order to produce food safely and in a sustainable way. This virtual issue presents principles and applications of agroecological engineering, exemplified in 19 selected review articles from the journal Agronomy for Sustainable Development, one of the most recognized journals in Agronomy. Practical examples of agroecological engineering include ecological pest control, intercropping, multiple cropping systems, biofertilisation, or the management of important components of agroecosystems such as ditches in landscapes, weeds and bees, and soil biodiversity. On the whole, this virtual issue covers a large range of topics and systems in temperate and tropical environments.

National audience; L’adaptation génétique, moteur de l’évolution, permet aux arbres de s’accommoder des modifications de leur environnement. Depuis le début des années 2000, des dépérissements forestiers massifs ont été observés dans toutes les régions du monde. Le stress hydrique qui a accompagné des canicules et des sécheresses plus intenses et plus fréquentes a entrainé des hécatombes d’arbres. Pour qu’une espèce puisse s’adapter, il faut que les individus favorisés survivent, se reproduisent et que l’avantage sélectif soit transmis à leurs descendants. Or le changement climatique est rapide et les arbres sont des organismes qui atteignent tardivement la maturité sexuelle : une course de vitesse s’engage entre l’évolution et le changement climatique. La recherche forestière tente de comprendre les causes des dépérissements et d’identifier les mécanismes physiologiques de la réponse aux stress climatiques, d’estimer le déterminisme génétique des caractères de résistance et de favoriser et accélérer les croisements entre individus adaptés.

Présenté devant un groupe coopératif d'industriels forestiers et d'universitaires brésiliens, à l'invitation du CIRAD et de l'Ambassade de France au Brésil, l'exposé donne un point de vue européen sur les forêts et le changement climatique, le situant en particulier vis-à-vis de la diversité des forêts françaises à objectif de production et de leurs contrastes avec les sylviculture de plantation brésiliennes. La communication cherche, au-delà des différences de contexte biogéographique, social et industriel, à montrer l'importance de l'itinéraire technique plantation dans la mise en œuvre des différentes options de changement de gestion.

This article presents an overview of the development of historical climatology during the past 50 years and how this discipline has contributed to a better understanding of past, present and future climate change. It not only shows how historical climatology has evolved from mainly the social sciences as a special field of research and how it operates, but also how it has spread among institutes, universities and meteorological services throughout Europe.Historical climatology studies written sources providing indirect information on weather conditions, ranging from rainfall, temperatures and air pressure to extreme weather events. Discussing the wide range of written sources, it is explained what kind of a climate signal they provide and how historical climatology has used this indirect climate information or proxy data by developing a methodology of its own, which aims to transfer the proxy data into reconstructed temperatures, rainfall and air pressure time series. Then the contribution of historical climatology to a better understanding of climate variability and its impact of the recent millennium will be discussed by showing the results reached so far. In this respect the paper strongly focuses on temperature change which occurred during the Little Ice Age and in particular the Maunder Minimum and weather extremes such as storm surges and their impact. Finally, perspectives for further research are discussed by focusing on the Low Countries. Cet article examine le développement de la climatologie historique au cours du dernier demi-siècle et montre comment elle a permis de mieux appréhender les changements climatiques passés, présents et futurs. Outre son fonctionnement, l’article montre comment cette discipline s’est développée à partir des sciences sociales pour devenir un domaine spécifique de recherche, et comment elle s’est propagée parmi les instituts, universités et services météorologiques à travers l’Europe.La climatologie historique étudie les sources écrites fournissant une information indirecte sur les conditions météorologiques, depuis le niveau des précipitations, la température et la pression atmosphérique jusqu’aux événements climatiques extrêmes. L’examen des multiples sources écrites permet de savoir quel type de signal climatique est fourni et comment la climatologie historique a utilisé ces informations indirectes en développant sa propre méthodologie visant à transformer ces indications en séries temporelles de reconstruction des températures, précipitations et pression atmosphérique.Nous verrons ensuite comment la climatologie historique a contribué à mieux appréhender la question de la variabilité du climat durant le dernier millénaire en présentant les résultats atteints jusqu’ici. A cet égard, l’article est fortement centré sur le changement de température intervenu au cours du Petit âge glaciaire, en particulier le Minimum de Maunder et les événements climatiques extrêmes comme les ondes de tempête et leur impact.Enfin, nous aborderons les perspectives de recherche aux Pays-Bas.

In this thesis, weathering of hiking trails has been studied in the low mountain ranges of the Massif Central (Auvergne, France) through the morphological comparison of four sectors in the Massif du Sancy and the Chaîne des Puys, each one presenting different erosion stages and rhythms of evolution. Our methodological approach is based on the crossing of three unpublished field datasets: topographic data, climate data and cartography of hiker behavior. High resolution topographic data mobilized three complementary data collection methods (terrestrial laser scanning, GPS monitoring and manual monitoring). Cross-analysis of all these data allowed us to: (1) quantify erosion and depositional volumes; (2) map the weathering sensitivity of studied areas; (3) identify the seasonality of weathering processes; (4) propose an operational evaluation tool for the management of hiking trails in low mountain ranges. Weathering quantification results show a clear differentiation of the studied areas. This contrasting erosion gradient has been proved to be linked to: local bioclimatic parameters which command the seasonality of weathering processes, irregular touristic attendance and substratum durability. In response to this erosion, varied management were introduced (guideline, wattle fence, low wall, water bars ...) and globally effective. Nevertheless, it appears that a refinement of the positioning adjustments, based on an understanding of weathering processes over a longer period would optimize the protective role of these structures., L’érosion des sentiers de moyenne montagne auvergnate est étudiée dans cette thèse à travers l’évolution morphologique de quatre secteurs présentant des stades d’érosion et des rythmes d’évolution différents, répartis dans le Massif du Sancy et la Chaîne des Puys. Notre approche méthodologique repose sur le croisement de trois jeux de données inédits collectés sur le terrain : relevés topographiques, données climatiques et cartographie du comportement des randonneurs. Les relevés topographiques fins mobilisent trois méthodes complémentaires de collecte de données (lasergrammétrie, GPS différentiel et relevés manuel). L’analyse croisée de l’ensemble de ces données nous a permis de : (1) quantifier des volumes d’érosion et de dépôt ; (2) cartographier les secteurs les plus sensibles à l’érosion ; (3) identifier une saisonnalité des processus érosifs ; (4) proposer un outil d’aide à la gestion des sentiers.Nos résultats de quantification de l’érosion des sentiers indiquent une différenciation des secteurs étudiés. Ce gradient d’érosion constaté s’explique par : le contexte climatique local qui commande la saisonnalité des processus d’érosion, la fréquentation touristique inégale et l’érodabilité du substrat. En réponse à cette érosion, nous avons observé la mise en place de divers aménagements (fils guide, fascines, murets, rigoles d’évacuation…), globalement efficaces. Néanmoins, il apparaît qu’un affinement du positionnement de ces derniers, sur la base d’une compréhension des processus érosifs sur un temps plus long, optimiserait le rôle protecteur de ces ouvrages.

National audience

Gene flow is an essential component of population adaptation and species evolution. Understanding of the natural and anthropogenic factors affecting gene flow is also critical for the development of appropriate management, breeding, and conservation programs. Here, we explored the natural and anthropogenic factors impacting crop-to-wild and within wild gene flow in apples in Europe using an unprecedented dense sampling of 1889 wild apple (Malus sylvestris) from European forests and 339 apple cultivars (Malus domestica). We made use of genetic, environmental, and ecological data (microsatellite markers, apple production across landscapes and records of apple flower visitors, respectively). We provide the first evidence that both human activities, through apple production, and human disturbance, through modifications of apple flower visitor diversity, have had a significant impact on crop-to-wild interspecific introgression rates. Our analysis also revealed the impact of previous natural climate change on historical gene flow in the nonintrogressed wild apple M. sylvestris, by identifying five distinct genetic groups in Europe and a north–south gradient of genetic diversity. These findings identify human activities and climate as key drivers of gene flow in a wild temperate fruit tree and provide a practical basis for conservation, agroforestry, and breeding programs for apples in Europe.

Bénéficiant de précipitations régulières et abondantes, la plupart des régions de polyculture élevage en Suisse sont favorables aux cultures herbagères. Les prairies semées occupent le deuxième rang des terres assolées et l’alimentation des herbivores est constituée de plus de 75 % d’herbe. Avec les changements climatiques, on s’attend à une augmentation des événements de sécheresse, en particulier dans l’ouest du pays. Les recherches en cours visent à adapter la composition et les modes d’exploitation des mélanges à cette contrainte. Ce travail s’appuie sur la connaissance des mécanismes de résistance au stress hydrique existant au sein des communautés végétales. Les prairies et les pâturages permanents du Jura, conditionnés par des sols karstiques et une mauvaise distribution des précipitations en été, offrent un terrain privilégié pour identifier les espèces et les écotypes susceptibles de convenir pour des conditions de sécheresse. Après des phases de sélection et d’assemblage d’espèces, les mélanges les plus performants sont distribués par les maisons de semences et bénéficient d’un label de qualité octroyé par l’Association pour le développement de la culture fourragère. Au sein d’un réseau de parcelles chez des agriculteurs, Agroscope réalise des mesures visant à adapter les modes d’exploitation et à optimiser la production des prairies semées, en particulier des fourrages stockés au printemps et de l’herbe pâturée en été., 168 Adaptation des prairies semées au changement climatique With regular and abundant rainfall, most mixed farming regions in Switzerland are favorable to grassland. Sown meadows occupy the second largest arable land surface and herbivorous diet consists on more than 75 % grass. With climate change, we expect an increase in drought events, especially in the western part of the country. Ongoing research aims to adapt the composition and management of grass-legumes mixtures to this constraint. This work is based on knowledge of the mechanisms of resistance to water stress within the plant communities. Permanent meadows and pastures of the Jura, conditioned by karst soils and poor distribution of rainfall in summer, offer a privileged field to identify species and ecotypes that may be suitable for dry conditions. After breeding and assembling species, the most effective mixtures are distributed by seed firms and enjoy a quality label granted by the Swiss grassland federation. Within a network of plots among farmers, Agroscope makes measurements to adapt the management and optimize the production of leys, especially stored forage in spring and grazed grass in summer.

La fin du Néolithique, au cours du IIIe millénaire BP, a correspondu à l’affaiblissement des périodes humides et à la mise en place de la géographie actuelle dans la zone sud-saharienne et sahélienne, qui s’étend de l’Atlantique au lac Tchad. Depuis cette époque le climat a cependant continué à beaucoup varier. La succession des différents épisodes climatiques, phases humides ou phases arides – et leurs interactions complexes –, est précisée. Ces faits climatiques sont mis en parallèle avec l’évolution archéologique et historique des différentes phases culturelles. Dans cette immense région, souvent à la limite de conditions naturelles extrêmes, les évènements climatiques ont toujours eu des conséquences très importantes sur l’évolution des peuplements humains. Le relativement bon synchronisme des principaux changements culturels, d’ouest en est à travers la bande sahélienne, paraît avoir été fréquemment contrôlé par le rôle directeur des changements climatiques majeurs et des variations environnementales qui en ont résulté. At the end of the Neolithic Era, during the third millennium BCE, there were fewer humid periods of weather, and the sub-Saharan Sahelian zone, from the Atlantic to Lake Chad, assumed its current geographical form. Since then, the climate has continued undergoing major variations. The succession of climatic episodes, humid or dry, is pointed out along with their complex interactions. These variations are placed in parallel to cultural phases of evolution in archeology and history. Climate-related events have always had heavy consequences on the peopling of this vast region, often subject to extreme natural conditions. The relative synchronism between the principal cultural trends from west to east across the Sahel seems to have often been subject to swings in the climate and the resulting environmental changes.

La fin du Néolithique, au cours du IIIe millénaire BP, a correspondu à l’affaiblissement des périodes humides et à la mise en place de la géographie actuelle dans la zone sud-saharienne et sahélienne, qui s’étend de l’Atlantique au lac Tchad. Depuis cette époque le climat a cependant continué à beaucoup varier. La succession des différents épisodes climatiques, phases humides ou phases arides – et leurs interactions complexes –, est précisée. Ces faits climatiques sont mis en parallèle avec l’évolution archéologique et historique des différentes phases culturelles. Dans cette immense région, souvent à la limite de conditions naturelles extrêmes, les évènements climatiques ont toujours eu des conséquences très importantes sur l’évolution des peuplements humains. Le relativement bon synchronisme des principaux changements culturels, d’ouest en est à travers la bande sahélienne, paraît avoir été fréquemment contrôlé par le rôle directeur des changements climatiques majeurs et des variations environnementales qui en ont résulté.At the end of the Neolithic Era, during the third millennium BCE, there were fewer humid periods of weather, and the sub-Saharan Sahelian zone, from the Atlantic to Lake Chad, assumed its current geographical form. Since then, the climate has continued undergoing major variations. The succession of climatic episodes, humid or dry, is pointed out along with their complex interactions. These variations are placed in parallel to cultural phases of evolution in archeology and history. Climate-related events have always had heavy consequences on the peopling of this vast region, often subject to extreme natural conditions. The relative synchronism between the principal cultural trends from west to east across the Sahel seems to have often been subject to swings in the climate and the resulting environmental changes.

Le présent travail a pour but de caractériser la variabilité du changement climatique et de ses effets sur les cultures fourragères selon les régions et les saisons. Récemment, plusieurs études sur ce thème, utilisant différents modèles et méthodes, ont été réalisées en France. Il s'agit donc de faire une synthèse de ces travaux qui, ayant utilisé des hypothèses de travail différentes, ont obtenu des résultats parfois différents. La multiplicité des méthodes a permis de montrer certains invariants dans le climat et les productions annuelles et saisonnières. L'avance printanière, l'existence de production hivernale et l'apparition ou l'accentuation du creux estival ont été mis en évidence - à des degrés divers - avec tous les modèles. La prévision d'une augmentation globale de production dans le futur proche fait également l'unanimité. Dans le futur, quelle que soit l'échéance, une augmentation est prévue principalement à cause des effets positifs du CO2, en particulier de la réduction de transpiration qu'il provoque. A long terme, les effets négatifs de la température et de l'augmentation de l'ETP risquent de dominer les effets positifs du CO2 et de provoquer une diminution globale de production : ce sont l'occurrence de cette diminution et son échéance qui font débat. Après analyse, l'augmentation de production dans le futur lointain, trouvée systématiquement avec un modèle d'une seule des deux études dont il est question ici, pourrait provenir de l'augmentation du rayonnement vue et utilisée dans cette étude, ainsi que d'une fertilisation beaucoup plus favorable., Recently, 4 simulation games using different models and methods were developed in France for characterizing climate change variability and its effect on forage crops, depending on the region and the season of year. A comparative analysis was used to determine global trends as well as possible causes of divergence. In the short term, results pointed to a global increase in production, and in the medium term, showed a spring advance, winter production, and a slump in the summer. In the longer term, a global decrease in production might be triggered by a high increase in temperature, the negative effect of lower rainfall, and the increase in ET, which the positive effect of higher CO2 levels may not manage to compensate. Certain factors (with regards to sunshine and fertilization) could explain these divergences between models.

International audience; Mediterranean landscapes are in a state of flux due to the impacts of changing land-use patterns and climate. Fuel–weather interactions determine that large, severe wildfires are increasingly common. Prescribed burning in southern Europe is therefore justified by the need to manage fire-prone vegetation types and maintain cultural landscapes that provide a range of ecosystem services. Prescribed fire has neutral or positive effects on soils and biodiversity, in contrast to wildfires, which can be extremely damaging. However, the limited extent of current applications are unlikely to reduce wildfire hazard or carbon emissions. Adoption of prescribed burning in the Mediterranean region has been slow, uneven, and inconsistent, and its development is constrained by cultural and socioeconomic factors as well as by specific factors related to demography, land use, and landscape structure. Sustainable fire management requires expansion of managers’ ability to use prescribed burning, a varied response to unplanned fires, and modified regulation of burning associated with traditional agricultural land uses.

International audience; The Mediterranean region is characterized by the presence of small catchments and intermittent water streams. Karst springs play an important role on the definition of river dynamics either in the temporal or spatial aspects, consequently, the intermittence of the river is explained by the karst springs regimes. This work aims at understanding the relationships between the triggering of water flow on karst springs with climatic characteristics, by the example of the Vène river karst springs (South-east Mediterranean coast of France). Climatic variables were calculated from rainfall characteristics such as height, intensity, duration, and antecedent cumulated amounts. The analysis of the springs' hydrographs allowed distinguishing rainfall events that could trigger the water flow on karst springs from rainfall events that could not trigger them. The results showed that the water flow triggering at the main spring was mainly related to cumulative rainfall amounts before the occurrence of the triggering rainfall event. This study contributed to a better understanding of the karst springs responses to climatic factors.

International audience

The spatio-temporal variability of the Choisille valley morpho-sedimentary evolution (catchment: 288 km²), a tributary of the middle Loire River in the south-western Parisian Basin (37), was studied through 78 core-drillings (8 transects), geophysical prospecting, sedimentological analyses and 14C and OSL dating. Eight phases of fluvial system evolution were defined and correlated with palynological and archaeological dataset, in order to highlight the impact of forcing factors: climate and/or human activity. From the Weichselian up to the Subatlantic, the fluvial incision or sedimentation activity has strictly evolved under climate control. Since the Allerød, this evolution was different from what has been observed on other rivers of north-western Europe, indicating regional climatic or geological specificities. Since the Bronze Ages, the river has evolved under climatic and human control; the anthropogenic impact on sedimentation was dominant, but spatio-temporaly variable in the catchment, in relationship with the agricultural potentialities of the different areas., La variabilité spatio-temporelle de l'évolution morpho-sédimentaire du fond de la vallée de la Choisille (bassin versant : 288 km²), affluent de la Loire moyenne dans le sud-ouest du Bassin parisien (37), a été étudiée par 78 forages (8 transects), prospection géophysique, analyses sédimentologiques et datations 14C et OSL. Huit phases d'évolution du système fluviatile depuis le début Weichsélien ont été définies et corrélées avec les données palynologiques et archéologiques locales, afin de comprendre l'impact des facteurs forçants : climat ou/et anthropisation. Du Weichsélien jusqu'au début du Subatlantique, l'activité d'incision ou de sédimentation de la Choisille a évolué sous contrôle climatique strict. Depuis l'Allerød, cette évolution a été différente de celles observées sur d'autres rivières en Europe du Nord-Ouest, indiquant des spécificités climatiques et géologiques régionales. Dès l'Âge du Bronze, la rivière a évolué sous contrôle climatique et anthropique ; l'impact anthropique sur la sédimentation fut prépondérant, mais très variable dans le temps et l'espace au sein du bassin selon les potentialités agricoles des secteurs considérés.

Ce nouveau livre blanc E4S passe en revue les options les plus importantes pour réduire l’impact climatique du transport aérien et les instruments envisagés ou mis en œuvre ailleurs dans le monde pour encourager une telle évolution. Il analyse en profondeur la taxe sur les billets d’avion de la loi révisée sur le CO2.