How self-regulation, the storage effect and their interaction contribute to coexistence in stochastic and seasonal environments

Explaining coexistence in species-rich communities of primary producers remains a challenge for ecologists because of their likely competition for shared resources. Following Hutchinson's seminal suggestion, many theoreticians have tried to create diversity through a fluctuating environment, which impairs or slows down competitive exclusion. However, fluctuating-environment models often only produce a dozen of coexisting species at best. Here, we investigate how to create richer communities in fluctuating environments, using an empirically parameterized model. Building on the forced Lotka-Volterra model of Scranton and Vasseur (Theor Ecol 9(3):353-363, 2016), inspired by phytoplankton communities, we have investigated the effect of two coexistence mechanisms, namely the storage effect and higher intra- than interspecific competition strengths (i.e., strong self-regulation). We tuned the intra/inter competition ratio based on empirical analyses, in which self-regulation dominates interspecific interactions. Although a strong self-regulation maintained more species (50%) than the storage effect (25%), we show that none of the two coexistence mechanisms considered could ensure the coexistence of all species alone. Realistic seasonal environments only aggravated that picture, as they decreased persistence relative to a random environment. However, strong self-regulation and the storage effect combined superadditively so that all species could persist with both mechanisms at work. Our results suggest that combining different coexistence mechanisms into community models might be more fruitful than trying to find which mechanism best explains diversity. We additionally highlight that while biomass-trait distributions provide some clues regarding coexistence mechanisms, they cannot indicate unequivocally which mechanisms are at play.Comment: 27 pages, 9 figures, Theor Ecol (2019

Analysing lexical richness in French learner language: what frequency lists and teacher judgements can tell us about basic and advanced words

We show how teacher judgements can be used to assess the quality of vocabulary used by L2 learners of French

Devenir du CODB dans les réseaux de distribution Etude de 2 cas

Cet article rapporte les résultats de campagnes de mesure de Carbone Organique Dissous Biodégradable sur 2 sites en exploitation. Les mesures de CODB ont été effectuées par la méthode rom et tom. La première partie de l'étude concerne le site de KERNE UHEL. Il s'agit d'une usine de traitement d'eau de surface comprenant une étape d'ozonation suivie d'une filtration sur CAG récemment mise en place. L'ozonation provoque une augmentation de CODB de 0,3 à 0,6 mg O. Le CAG élimine le CODB : on a 100 % d'élimination lorsqu'il est neuf, et jusqu'à 80 % d'élimination sur un pilote après 1 an de fonctionnement. Dans le réseau, an observe une diminution du CODB lorsque la concentration de celui-ci est de 0,6 - 0,7 mg 1-1 dans l'eau traitée, cela malgré la présence de chlore libre. Lorsque le CODB de l'eau traitée est de 0,14 mgl-1 (après mise en route de la filière CAG) l'évolution dans le réseau est beaucoup plus difficile à mesurer (0,14 < CODB < 0,27 mg l-1). Le deuxième site étudié est le réseau de VIENNE-BRIANCE. 4 campagnes de mesures effectuées entre Juin et Août 1991 sur 10 points de prélèvement, montrent qu'il y a consommation de CODB, surtout en période chaude et aux extrémités du réseau. On a également des relargages de CODB, un nombre significatif de valeurs se trouvant au-dessus de la valeur maximale observée à l'usine. On remarque une grande variabilité des valeurs sur le réseau (< 0,1 à 0,6 mg l-1) en comparaison avec la gamme de valeurs obtenues sur l'eau traitée (0,21- 0,30 mg l-1).This study reports results of BDOC measurements from two experimental sites. BDOC was measured by JORET and LEVI’S method, in which a sample is incubated at 20 °C with colonised sand. Dissolved Organic Carbon is evaluated every day, and BDOC calculated as Initial DOC minus the minimal DOC observed during incubation. Reliability of this method was verified by measuring BDOC of standard acetate solutions. We obtained coefficients warrying between 2 and 5 % for BDOC about 1,0 mg l-1.The first part of the study concerns KERNE UHEL treatment plant and its distribution network. BDOC was measured on sand filtered water, ozonated water, GAC filtered water, treated water and on five reservoirs along the network. Results from the treatment plant show that ozonation generates BDOC (increase of 0.3 to 0.6 mg l-1) GAC filtration allows very low levels of BDOC to be obtained when filtration start up (< 0.1 mg l-1) On GAC pilot plant, BDOC removed was between 50 % and 80 % after one year. In distribution, BDOC concentration 'decreased tram 0,6 - 0,7 mg l-1 to 0,2 - 0,4 mgl-1, during an estimated residence lime of 190 h. When the entire GAC filters were commissioned on the treatment plant, treated water BDOC was equal to 0.14 mg l-1; and between 0.14 and 0.27 mg l-1 in the network. This shows that BDOC reduction in the treatment plant reduces its evolution in the distribution system.The second part of the study was conducted on the distribution network of VIENNE BRIANCE, which is supplied with water from the river VIENNE. This water is treated by coagulation, settlement and sand filtration. This network is very extensive and provides water to more than 20 rural villages. Ten points were selected on the network, and were monitored for BDOC, chemical and bacteriological parameters from June to August 1991. Results of physico chemical analyses showed variation of temperature (-3 °C to + 3 °C in the network compared to the treated water at the station); pH (slight variations < 0,5 pH units) and turbidity (increase in the network with peak values as high as 3,5 NTU). Treatment plant's BDOC values were between 0.2 - 0.4 mg l-1. In the network, a great variation is observed : < 0.1 to 0.6 mg l-1. This shows that microbiological activity in the system causes BDOC consumption, but also BDOC is released kilo the water. Heterotrophic bacteria coutils increases during distribution and filamentous fungi have also been isolated in this network.The results of this study pointed out the difficulty to interprete BROC evolution in the network, especially when the hydraulic of the system is not well understood

Enteric viruses : current knowledge and control methods in the agri-food industry

Enteric viruses are released in large quantities into the environment, where they can persist for a very long time. They are infectious at very low doses for humans, and are responsible for a significant number of foodborne intoxications and infections every year worldwide. Feco-oral transmission occurs mainly through the ingestion of contaminated food, either fresh or inadequately processed (industrially or at home), and through human contacts. There are currently no regulatory constraints, due to the lack of standardised tools, to identify these pathogens. However, the European Community is currently evaluating methods to extract and detect by molecular biology enteric viruses in liquids and food matrices. These methodological developments are expected to generate, in the medium term, virological standards for the main foodstuffs at risk. The industry will have to control the risk of viral contamination as part of an overall HACCP approach, using these tools as well as risk analysis and specific control measures.Les virus entériques sont rejetés en grande quantité dans l'environnement où ils sont capables de persister très longtemps. Ils sont infectieux à très faibles doses pour l'homme, et à l'origine d'un nombre important de toxi-infections alimentaires chaque année dans le monde. Leur transmission féco-orale se fait principalement par la consommation d'aliments contaminés, consommés frais ou n'ayant pas subi de traitement industriel ou domestique suffisant, ainsi que par les contacts interhumains. Il n'existe à l'heure actuelle aucune contrainte réglementaire, du fait d'un manque d'outils standardisés de recherche de ces pathogènes. Néanmoins, des méthodes, permettant l'extraction et la détection par biologie moléculaire des virus entériques dans les liquides et matrices alimentaires, sont en cours d'élaboration par la Communauté Européenne. Ces développements méthodologiques devraient aboutir, à moyen terme, à la mise en place de normes fixant des critères virologiques pour les principaux aliments à risque. La maîtrise du risque viral au niveau industriel devra s'appuyer sur ces outils d'autocontrôles, en les intégrant dans une démarche HACCP globale, basée sur une analyse des risques et des mesures de contrôle spécifiques

Symmetric hysteresis curves of rare earth-cobalt magnets measured by high magnetic fields

SmCo5magnets show generally asymmetrical hysteresis curves in the region of ordinary magnetic field strength. However, if these magnets are magnetized by a field of over 14 T, hysteresis loop becomes symmetric, except for the experimental errors caused by the thermal fluctuation after effect. The influence of the after effect on the magnetization curve and the coercive forceIHCare discussed.</p

Picard: a mal aimé among regional languages?

Although often seen as a medieval rival to French, Picard has received far less official recognition and support than more celebrated regional languages such as Breton or Occitan. A shared history and high degree of linguistic similarity with the national language appear to have engendered a perception that it is simply ‘bad French’, but for supporters such Eloy (1997) Picard remains potentiellement une vraie langue, worthy and in need of status enhancement initiatives enjoyed by other regional languages. Promotion of language status for Picard, however, is found to be fraught with practical difficulties, not least of which are a lack of territorial unity and major cultural differences between the north and south of the picardophone area. Equally importantly, the discourse of languagehood fosters notions of linguistic purity which ignore the extensive mixing of local, supralocal and national elements that has always been evident in Picard writing and speech. This in turn engenders linguistic insecurity, notably among urban working-class speakers, whose speech can all too easily be caricatured as both ‘bad French’ and ‘bad patois’, with obvious consequences for intergenerational transmission. The well-intentioned promotion of Picard as a regional language may therefore, perversely, be detrimental to the very varieties it serves

Post-Franco Theatre

In the multiple realms and layers that comprise the contemporary Spanish theatrical landscape, “crisis” would seem to be the word that most often lingers in the air, as though it were a common mantra, ready to roll off the tongue of so many theatre professionals with such enormous ease, and even enthusiasm, that one is prompted to wonder whether it might indeed be a miracle that the contemporary technological revolution – coupled with perpetual quandaries concerning public and private funding for the arts – had not by now brought an end to the evolution of the oldest of live arts, or, at the very least, an end to drama as we know it