Evolution of the agri-environmental schemes and its effects on perceptions and practices of sheep farmers in Luberon. (Provence-Alpes-côte d’Azur, France)

Pionnier en matière de contractualisation agri-environnementale, le Parc du Luberon est un témoin de l’évolution de ces mesures sur son territoire. À travers des enquêtes réalisées en 2010 auprès d’éleveurs ovins pâturant sur le territoire du Parc du Luberon, cet article se propose de comprendre comment l’adhésion à ce type de contrat influence la perception que l’éleveur a de son métier et de la façon dont il envisage le fonctionnement de son exploitation. L’évolution de ces contrats renvoie également à la manière dont interagissent dynamiques d’élevage et dynamiques écologiques.Pioneer to agri-environmental schemes, the Luberon Nature Regional Park is a witness of the evolution of these actions within its territory. Through field investigations led in 2010 among sheep farmers, our goal is to understand how the engagement to this kind of schemes affects both perception of sheep farming and the exploitation system coherence. The evolution of these schemes also refers to the interactions between breeding and ecological dynamics

Diversité des archées et implication de la composante procaryote dans le cycle biogéochimique du méthane en milieu aquatique continental (études taxonomiques et fonctionnelles dans la colonne d'eau et les sédiments anoxiques du lac Pavin)

Le méthane, un des principaux gaz à effet de serre, est majoritairement produit et consommé par l'activité métabolique de microorganismes affiliés aux domaines des Archaea et des Bacteria. Afin d appréhender le cycle biogéochimique du méthane, il est essentiel d identifier l ensemble des acteurs impliqués dans ce dernier ainsi que les facteurs environnementaux modulant leurs activités. Les lacs d eau douce constituent une source importante de méthane, car, dans ces écosystèmes, les conditions environnementales favorisent la méthanogenèse au détriment d autres processus terminaux de la dégradation anaérobie de la matière organique. Au cours de cette thèse, les études sur les communautés impliquées dans le cycle biogéochimique du méthane ont été conduites dans la colonne d eau et les sédiments anoxiques du Lac Pavin (Auvergne), unique lac méromictique de France. Cet écosystème a été choisi comme site d'étude en raison des fortes concentrations en méthane présentes dans sa couche d'eau profonde qui contrastent avec les faibles émissions de ce gaz vers l'atmosphère. Ces observations géochimiques suggèrent une intense activité de production et de consommation du méthane, offrant un cadre pertinent pour l étude des communautés ciblées. Les approches moléculaires visant à caractériser la structure spatiale, la composition, les zones d'activité et les facteurs (ascendants et descendants) potentiellement impliqués dans la régulation des communautés de méthanogènes et de méthanotrophes ont été, au cours de ce travail, systématiquement associées à des approches culturales et microcalorimétriques afin d acquérir des données sur la physiologie des microorganismes impliqués dans le cycle du méthane. Les résultats obtenus mettent en évidence que les communautés de méthanogènes sont distribuées sur l ensemble de la colonne d eau anoxique et dans la strate superficielle des sédiments profonds. Ce groupe métabolique, essentiellement représenté par des espèces affiliées aux Methanosaetaceae et aux Methanoregulaceae, est particulièrement actif dans la zone benthique qui constituerait la source principale de méthane dans cet écosystème. Une nouvelle espèce méthanogène, Methanobacterium lacus, a été isolée de ces sédiments et décrite, et vient enrichir le faible nombre d'espèces méthanogènes isolées à ce jour à partir des lacs d'eau douce. L'étude écophysiologique de cette souche suggère que la température pourrait en partie expliquer la faible représentativité des Methanobacteriales dans cet écosystème. Une partie du méthane semble être directement consommée dans la zone anoxique (pélagique et benthique). L existence de ce processus d oxydation anaérobie, soutenu par les approches microcalorimétriques, pourrait être, dans les sédiments profonds, sous la dépendance de lignées candidates archéennes dont la physiologie reste encore énigmatique. Le remplacement progressif des méthanogènes par 2 lignées candidates d'archaea (MBG-D et MCG) le long du profil sédimentaire suggère qu'elle se développe dans des niche contrastées. La régulation putative des communautés archéennes par les virus a été analysée. Cette étude est la première à rapporter la présence de particules virales de type "archaeovirus" dans un environnement non-extrême (en termes de température, pH et salinité) ainsi que des particules virales pouvant représentées de nouvelles familles de virus. Une activité virale intense est suggérée dans ces sédiments par le nombre important de cellules infectées, comparativement à d'autres sédiments, et par le changement concomitant de la structure de la communauté virale et procaryotique avec la profondeur. Bien qu une partie du méthane soit probablement oxydée en anaérobiose, la consommation de ce métabolite est principalement dépendante de l activité de méthanotrophes aérobies dominées par des espèces affiliées au genre Methylobacter, un des principaux genres de méthanotrophes rencontré en milieu d eau douce. (...)Methane, a major greenhouse gas, is produced and consumed mainly by the metabolic activity of microorganisms affiliated to the domains Archaea and Bacteria. In order to understand the biogeochemical cycling of methane, it is essential to identify all the biological actors involved, as well as environmental factors modulating their activity. Freshwater lakes are a major source of methane because environmental conditions occurring in these ecosystems favor methanogenesis over other terminal processes of anaerobic degradation of organic matter. In this thesis, studies of communities involved in the biogeochemical cycling of methane were carried out in the water column and anoxic sediment of Lake Pavin (Auvergne), the unique French meromictic lake. This ecosystem has been selected as study site due to the high concentrations of methane in its deep water layer which contrast with the very low emission of this gas in the atmosphere. These geochemical observations suggest an intense activity of production and consumption of methane, providing an appropriate framework for studying the communities involved. Molecular approaches to characterize the spatial structure, composition, activity areas and factors (bottom-up and top-down) potentially involved in the regulation of methanogens and methanotrophs were, in this work, systematically associated to cultural and microcalorimetric approaches to acquire data on the physiology of microorganisms involved in the methane cycle. The results show that methanogens are distributed throughout the permanent anoxic water column (monimolimnion) and mainly in the superficial layer of the sediment situated under the monimolimnion. This metabolic group, mainly represented by species affiliated to Methanosaetaceae and Methanoregulaceae, is particularly active in the benthic zone which would be the main source of methane in this ecosystem. A new species of methanogen, Methanobacterium lacus, was isolated from these sediments and described. It enhances to the small number of methanogenic species isolated to date from freshwater lakes. The ecophysiological study of this strain suggests that the temperature could partly explain the low representation of Methanobacteriales in this ecosystem. A part of the methane appears to be directly consumed in the anoxic zone (pelagic and benthic). The existence of this process of anaerobic oxidation, supported by microcalorimetric approaches, could be in deep sediments, dependent on archaeal candidate lineages whose physiology remains enigmatic. The gradual replacement of methanogens by two archaeal candidate lineages (MBG-D and MCG) along the sedimentary profile suggests that they live in contrasted niche. The putative regulation of the archaeal communities by virus was analyzed. This study has reported the first observations of archaeovirus-like particles in a non-extreme environment (in term of temperature, pH and salinity) and virus-like particles which might represent new viral families. An intense viral activity in these sediments is suggested by i) the important number of visibly infected cells and ii) the concomitant change of the viral and prokaryotic communities with depth. While a fraction of methane is probably oxidized anaerobically, the consumption of this metabolite is mainly dependent on the activity of aerobic methanotrophs dominated by species affiliated to the genus Methylobacter, one of the main types of methanotrophs found in freshwater environments.These methanotrophs have a large area of activity, extending around both sides of the red/ox interface in the water column. This wide distribution may partly explain the low quantity of methane released by the Lake Pavin. (...)CLERMONT FD-Bib.électronique (631139902) / SudocSudocFranceF

Grassy areas on the crests of the Luberon, sentinels of the global warming - Evolution of the grazed ecosystems during thirty years, from 1982 to 2011

Les crêtes du Luberon sont occupées par des pelouses méditerranéo- montagnardes à forte biodiversité. Ces écosystèmes soumis à des conditions climatiques difficiles sont façonnés depuis des siècles par l’action de troupeaux ovins conduits en gardiennage. Depuis quelques décennies, ces pelouses sont menacées par la déprise pastorale, l’érosion causée par la fréquentation motorisée, les dégâts croissants de sangliers, enfin les accidents climatiques répétés de cette dernière décennie. Le PNRL, avec le CERPAM, l’ONF et l’appui de la recherche (INRA d’Avignon, Université d’Aix-Marseille) a animé depuis plus de trente ans des actions de conservation de ces habitats en confortant l’élevage pastoral (réouverture des milieux, équipements pastoraux, mesures agri-environnementales). Un bilan est dressé de l’évolution des pelouses sommitales du Luberon en mobilisant divers suivis mis en place depuis 1982 pour les plus anciens, permettant de comparer pelouses pâturées et non pâturées. Cette synthèse concerne principalement le Grand Luberon, dans une moindre mesure le Petit Luberon. Durant cette période, les chargements ont fortement baissé sur le Grand Luberon alors que le niveau de ressource pastorale est resté stable. Cette baisse s’explique dans le cadre d’un moindre besoin de la part des éleveurs du piémont utilisateurs des crêtes, d’une moindre incitation agri-environnementale dans le cadre des MAET Natura 2000, enfin de pratiques de garde qui ont évolué vers un pâturage moins « serré ». Les suivis pastoraux confirment un maintien de la ressource pastorale, mais avec l’apparition de trouées colonisées par des graminées opportunistes, résultant sans doute de la canicule de 2003 et des sécheresses des années suivantes. Les suivis de biodiversité effectués dans les deux massifs montrent une évolution contrastée d’un certain nombre d’espèces floristiques phares. Mais les baisses dominent, notamment pour Genista pulchella subsp. villarsii, Anthyllis montana, Plantago argentea, Sempervivum calcareum, Valeriana tuberosa, Ephedra nebrodensis ; les résultats sont comparables avec et sans pâturage, ce qui suggère fortement une cause climatique: répétition des canicules et sécheresses entre 2003 et 2006, et/ou début du réchauffement climatique documenté dans notre région depuis la fin des années 1970.Luberon’s crests are occupied by mediterraneo-mountain grassy areas with strong biodiversity. These ecosystems affected by difficult climatic conditions have been shaped for centuries by the action of guarded ovine herds. Since a few decades, these areas are threatened by the decrease of pasture, the erosion caused by motorized circulation, increasing damages of wild boars, and the repeated climatic incidents of the last decade. For more than thirty years, the PNRL, with the CERPAM and the ONF, and with the support of research centers (INRA of Avignon, University of Aix-Marseille), has developed actions to preserve these natural ecosystems by consolidating the pastoral breeding (reopening of the environment, pastoral equipments, agri-environmental measures). A balance sheet of the evolution of sommitals grassland of Luberon is drawn up by mobilizing some follow-ups set up since 1982, allowing to compare grazed and non-grazed grasslands. This synthesis concerns mainly the Grand Luberon, and to a lesser extent the Petit Luberon. During this period, loads strongly decreased on Grand Luberon, while the level of pastoral resource remained stable. This decline can be explained by a lesser need of the breeders from piedmont, using crests, by a lesser agri-environmental incitement within Natura 2000, and by practices of guarding which evolved towards a « less tight » pasture. The follow-ups confirm a preservation of the pastoral resource, but with the appearance of places colonized by opportunist grasses, resulting from the heat wave of 2003 and from the droughts of the next years. The follow-ups of biodiversity made in both massifs show a contrasted evolution for a certain number of key floral species. But many species decline, in particular Genista pulchella ssp. villarsii, Anthyllis montana, Plantago argentea, Sempervivum calcareum, Valeriana tuberosa, Ephedra nebrodensis. The results are comparable with and without pasture, and this strongly suggests a climatic cause : repetition of the heat waves and the droughts between 2003 and 2006, and\or at the beginning of the global warming informed in our region since the end of 1970s

Secondary metabolites from Spirotropis longifolia (DC) Baill and their antifungal activity against human pathogenic fungi

A phytochemical study of the ethyl acetate extract of the roots and adventitious roots of Spirotropis longifolia, a monodominant tree species of the Guianan rainforest, has allowed the isolation of three compounds: 2- hydroxy-8,9-methylenedioxy-2',2'-dimethylpyrano-[5',6':4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin A), 2-hydroxy-8,9-methylenedioxy-2',2'-dimethy1-3',4'-dihydropyrano-[5',6':4,3]-6a-prenyl-(6aS,11aS]-pterocarpan (spirotropin B), and 5,7-dihydroxy-6.8-dipreny1-2 ''''.2 ''''-dimethylpyrano[5 '''',6 '''': 3',4]-isoflavone (spirotropone). In addition, 10 known compounds, trans-oxyresveratrol, trans-resveratrol, piceatannol, daidzein, genistein, isoprunetin, lupeol, latifolol, gnetin D and gnetin E, were also isolated. These compounds were evaluated for their antifungal activity and their cytotoxicity, and their structures were established by 1D and 2D NMR, HRMS, CD and optical rotation measurements. (C) 2011 Elsevier Ltd. All rights reserved.CNRS (France)CAPESCNPqFAPESPFAPDF (Brazil

Relationships between species richness and ecosystem services in Amazonian forests strongly influenced by biogeographical strata and forest types

Despite increasing attention for relationships between species richness and ecosystem services, for tropical forests such relationships are still under discussion. Contradicting relationships have been reported concerning carbon stock, while little is known about relationships concerning timber stock and the abundance of non-timber forest product producing plant species (NTFP abundance). Using 151 1-ha plots, we related tree and arborescent palm species richness to carbon stock, timber stock and NTFP abundance across the Guiana Shield, and using 283 1-ha plots, to carbon stock across all of Amazonia. We analysed how environmental heterogeneity influenced these relationships, assessing differences across and within multiple forest types, biogeographic regions and subregions. Species richness showed significant relationships with all three ecosystem services, but relationships differed between forest types and among biogeographical strata. We found that species richness was positively associated to carbon stock in all biogeographical strata. This association became obscured by variation across biogeographical regions at the scale of Amazonia, resembling a Simpson’s paradox. By contrast, species richness was weakly or not significantly related to timber stock and NTFP abundance, suggesting that species richness is not a good predictor for these ecosystem services. Our findings illustrate the importance of environmental stratification in analysing biodiversity-ecosystem services relationships

Climate Change Impact on Neotropical Social Wasps

Establishing a direct link between climate change and fluctuations in animal populations through long-term monitoring is difficult given the paucity of baseline data. We hypothesized that social wasps are sensitive to climatic variations, and thus studied the impact of ENSO events on social wasp populations in French Guiana. We noted that during the 2000 La Niña year there was a 77.1% decrease in their nest abundance along ca. 5 km of forest edges, and that 70.5% of the species were no longer present. Two simultaneous 13-year surveys (1997–2009) confirmed the decrease in social wasps during La Niña years (2000 and 2006), while an increase occurred during the 2009 El Niño year. A 30-year weather survey showed that these phenomena corresponded to particularly high levels of rainfall, and that temperature, humidity and global solar radiation were correlated with rainfall. Using the Self-Organizing Map algorithm, we show that heavy rainfall during an entire rainy season has a negative impact on social wasps. Strong contrasts in rainfall between the dry season and the short rainy season exacerbate this effect. Social wasp populations never recovered to their pre-2000 levels. This is probably because these conditions occurred over four years; heavy rainfall during the major rainy seasons during four other years also had a detrimental effect. On the contrary, low levels of rainfall during the major rainy season in 2009 spurred an increase in social wasp populations. We conclude that recent climatic changes have likely resulted in fewer social wasp colonies because they have lowered the wasps' resistance to parasitoids and pathogens. These results imply that Neotropical social wasps can be regarded as bio-indicators because they highlight the impact of climatic changes not yet perceptible in plants and other animals

Water Availability Is the Main Climate Driver of Neotropical Tree Growth

• Climate models for the coming century predict rainfall reduction in the Amazonian region, including change in water availability for tropical rainforests. Here, we test the extent to which climate variables related to water regime, temperature and irradiance shape the growth trajectories of neotropical trees. • We developed a diameter growth model explicitly designed to work with asynchronous climate and growth data. Growth trajectories of 205 individual trees from 54 neotropical species censused every 2 months over a 4-year period were used to rank 9 climate variables and find the best predictive model. • About 9% of the individual variation in tree growth was imputable to the seasonal variation of climate. Relative extractable water was the main predictor and alone explained more than 60% of the climate effect on tree growth, i.e. 5.4% of the individual variation in tree growth. Furthermore, the global annual tree growth was more dependent on the diameter increment at the onset of the rain season than on the duration of dry season. • The best predictive model included 3 climate variables: relative extractable water, minimum temperature and irradiance. The root mean squared error of prediction (0.035 mm.d–1) was slightly above the mean value of the growth (0.026 mm.d–1). • Amongst climate variables, we highlight the predominant role of water availability in determining seasonal variation in tree growth of neotropical forest trees and the need to include these relationships in forest simulators to test, in silico, the impact of different climate scenarios on the future dynamics of the rainforest

Biased-corrected richness estimates for the Amazonian tree flora

Amazonian forests are extraordinarily diverse, but the estimated species richness is very much debated. Here, we apply an ensemble of parametric estimators and a novel technique that includes conspecific spatial aggregation to an extended database of forest plots with up-to-date taxonomy. We show that the species abundance distribution of Amazonia is best approximated by a logseries with aggregated individuals, where aggregation increases with rarity. By averaging several methods to estimate total richness, we confirm that over 15,000 tree species are expected to occur in Amazonia. We also show that using ten times the number of plots would result in an increase to just ~50% of those 15,000 estimated species. To get a more complete sample of all tree species, rigorous field campaigns may be needed but the number of trees in Amazonia will remain an estimate for years to come

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types