Aperçu sur les forêts anciennes et matures de Méditerranée française et des montagnes limitrophes - Enjeux pour la conservation de la nature

Cet article propose un aperçu de la naturalité de 52 peuplements représentatifs de la diversité des hauts lieux forestiers de 15 départements du sud de la France. En moyenne, ils sont caractérisés par une diversité des arbres élevée ; une grande densité de microhabitats ; une structure irrégulière ; une surface terrière > 25 m2/ha ; un âge du peuplement avancé ; un nombre de très très gros bois > 10 TTGB/ha et un volume de bois mort parfois > 50 m3/ha ; une dynamique dominée par les dryades, mais avec une sylvigenèse souvent incomplète. L’empreinte humaine est généralement faible après 1960 mais importante auparavant (pâturage, charbonnage, etc.). La non exploitation du bois est attestée depuis 1880 à La Massane, 1886 à Comus et 1897 à Lente. Les analyses conduisent à l’ordination des peuplements suivant leur naturalité relative. Ceux de plus haute naturalité sont des sapinières ou hêtraies-sapinières (Bois noir de Breil, Zonza, Bois du Chapitre) ou hêtraie (Ventoux, Zicavo, La Massane). Pour les autres habitats, la chênaie verte du Fango–Omita et la chênaie blanche de Montchamp à Païolive sont à remarquer. Ces résultats ouvrent une discussion et des perspectives d’application à la gestion, qu’elle soit productiviste ou conservatoire

Mettre en œuvre un réseau d’îlots de vieux bois - Test d’une méthode dans la Réserve de biosphère du mont Ventoux -

Le réseau d’îlots de vieux bois est un outil nouveau pour conserver notamment la riche biodiversité cavicole et saproxylique. Après avoir analysé la littérature, une méthodologie générique de mise en œuvre, organisée en sept étapes, est proposée, ainsi que des outils pratiques. Elle est testée dans le mont Ventoux. Un scénario défini de façon participative conduit à un réseau d’îlots de sénescence fondé sur des indicateurs de naturalité (indigénat, maturité, ancienneté, connectivité), de même qu’une approche centrée sur les espèces, le manque à gagner économique et la sécurité du public. La surface du réseau d’îlots est limitée à 3% de la surface de la forêt. La méthode Electre est utilisée pour classer les 132 îlots pré-repérés, au regard du scénario élaboré. 74 îlots sont retenus pour le réseau. Les valeurs écologiques sont maximisées. Le manque à gagner est minimisé (66% des îlots retenus présentent un manque à gagner < 20 e/ha/an). La révision de l’aménagement de la forêt domaniale du Ventouret en 2012 a permis la mise en place de quatre premiers îlots, dont un a été financé par Natura 2000. La méthode permet de bien évaluer et hiérarchiser l’intérêt de chaque îlot et de discuter la notion de réseau. Elle est disponible pour être confrontée à des contextes écologiques variés

Risk assessment for the spread of Serratia marcescens within dental-unit waterline systems using Vermamoeba vermiformis

Vermamoeba vermiformis is associated with the biofilm ecology of dental-unit waterlines (DUWLs). This study investigated whether V. vermiformis is able to act as a vector for potentially pathogenic bacteria and so aid their dispersal within DUWL systems. Clinical dental water was initially examined for Legionella species by inoculating it onto Legionella selective-medium plates. The molecular identity/profile of the glassy colonies obtained indicated none of these isolates were Legionella species. During this work bacterial colonies were identified as a non-pigmented Serratia marcescens. As the water was from a clinical DUWL which had been treated with Alpron™ this prompted the question as to whether S. marcescens had developed resistance to the biocide. Exposure to Alpron™ indicated that this dental biocide was effective, under laboratory conditions, against S. marcescens at up to 1x108 colony forming units/millilitre (cfu/ml). V. vermiformis was cultured for eight weeks on cells of S. marcescens and Escherichia coli. Subsequent electron microscopy showed that V. vermiformis grew equally well on S. marcescens and E. coli (p = 0.0001). Failure to detect the presence of S. marcescens within the encysted amoebae suggests that V. vermiformis is unlikely to act as a vector supporting the growth of this newly isolated, nosocomial bacterium

Intrinsic Stability of Temporally Shifted Spike-Timing Dependent Plasticity

Spike-timing dependent plasticity (STDP), a widespread synaptic modification mechanism, is sensitive to correlations between presynaptic spike trains and it generates competition among synapses. However, STDP has an inherent instability because strong synapses are more likely to be strengthened than weak ones, causing them to grow in strength until some biophysical limit is reached. Through simulations and analytic calculations, we show that a small temporal shift in the STDP window that causes synchronous, or nearly synchronous, pre- and postsynaptic action potentials to induce long-term depression can stabilize synaptic strengths. Shifted STDP also stabilizes the postsynaptic firing rate and can implement both Hebbian and anti-Hebbian forms of competitive synaptic plasticity. Interestingly, the overall level of inhibition determines whether plasticity is Hebbian or anti-Hebbian. Even a random symmetric jitter of a few milliseconds in the STDP window can stabilize synaptic strengths while retaining these features. The same results hold for a shifted version of the more recent “triplet” model of STDP. Our results indicate that the detailed shape of the STDP window function near the transition from depression to potentiation is of the utmost importance in determining the consequences of STDP, suggesting that this region warrants further experimental study

Rapid diagnostic tests relying on antigen detection from stool as an efficient point of care testing strategy for giardiasis and cryptosporidiosis? Evaluation of a new immunochromatographic duplex assay

Microscopy is the gold standard for the diagnosis of gastrointestinal parasites but is time-consuming and dependent on operator skills. Rapid diagnostic tests represent alternative methods but most evaluations have been conducted on a limited number of samples preventing their implementation in the clinical setting. We evaluated a new CE-IVD marked immunochromatographic assay (Crypto/Giardia K-SeT®, Coris Bioconcept) for the detection of G. intestinalis and Cryptosporidium spp. in 2 phases (retrospective and prospective) on a set of 482 stool samples including rare Cryptosporidium species. Besides G. intestinalis, this test could represent a rapid and reliable alternative to the modified Ziehl-Neelsen staining for the diagnosis of cryptosporidiosis (sensitivity/specificity were 89.2%/99.3% and 86.7%/100% for G. intestinalis and Cryptosporidium resp.), reducing diagnostic delays. Such strategy would also be time-saving by avoiding wet mount microscopy and concentrations steps, being particularly appropriate for laboratories having little expertise in microscopy or not able to implement molecular diagnostic methods

The contribution of insects to global forest deadwood decomposition

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks. The decomposition of deadwood is largely governed by climate with decomposer groups—such as microorganisms and insects—contributing to variations in the decomposition rates. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect—including the direct consumption by insects and indirect effects through interactions with microorganisms—insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and −0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle

Kaart van Suriname, naar de opmetingen gedaan in de jaren 1860-1879 / door J.-F. Cateau van Rosevelt ; en J. F. A. E. van Lansberge...

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