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Groc, S., Delabie, J. H. C., Fernández, F., Leponce, M., Orivel, J., Silvestre, R., et al. (2013). Leaf-litter ant communities in a pristine Guianese rainforest: stable functional structure versus high species turnover. Myrmecol. News, 19, 43–51.
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Salhi, L., Nait-Rabah, O., Deyrat, C., & Roos, C. (2013). Numerical Modeling of Single Helical Pile Behavior under Compressive Loading in Sand. Electron. J. Geotech. Eng., 18(Bundle T), 4119–4338.
Abstract: The present research deals with helical piles behavior in cohesionless soil through finite element modeling. An approach of modeling of the screw-pile geometry has been proposed through the Finite Element Analysis (FEA) computer program Plaxis. The numerical results are compared with measurements from large scale test and the bearing capacity has been estimated using both cylindrical and individual bearing model. Moreover, different failure criterions have been applied to estimate the ultimate capacity. The effect of spacing ratio (S/Dh) on the screw-pile behavior has been further studied. It has found that results from the model fit the field results. Through the study of the load transfer mechanism, the transition from cylindrical shear to individual plate behavior occurs at a value of spacing ratio (1.5 to 2).
Keywords: helical pile; finite element method; failure mechanisms; sand
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Woolfit, M., Iturbe-Ormaetxe, I., Brownlie, J. C., Walker, T., Riegler, M., Seleznev, A., et al. (2013). Genomic evolution of the pathogenic Wolbachia strain, wMelPop. Genome Biolog. Evol., 5(11), 2189–2204.
Abstract: Most strains of the widespread endosymbiotic bacterium Wolbachia pipientis are benign or behave as reproductive parasites. The pathogenic strain wMelPop is a striking exception, however: it overreplicates in its insect hosts and causes severe life shortening. The mechanism of this pathogenesis is currently unknown. We have sequenced the genomes of three variants of wMelPop and of the closely related nonpathogenic strain wMelCS. We show that the genomes of wMelCS and wMelPop appear to be identical in the nonrepeat regions of the genome and differ detectably only by the triplication of a 19-kb region that is unlikely to be associated with life shortening, demonstrating that dramatic differences in the host phenotype caused by this endosymbiont may be the result of only minor genetic changes. We also compare the genomes of the original wMelPop strain from Drosophila melanogaster and two sequentialderivatives, wMelPop-CLA and wMelPop-PGYP. To develop wMelPop as a novel biocontrol agent, it was first transinfected into and passaged in mosquito cell lines for approximately 3.5 years, generating wMelPop-CLA. This cell line-passaged strain was then transinfected into Aedesaegypti mosquitoes, creating wMelPop-PGYP,which wassequenced after 4yearsin the insecthost. We observe a rapid burst of genomic changes during cell line passaging, but no further mutations were detected after transinfection into mosquitoes, indicating either that host preadaptation had occurred in cell lines, that cell lines are a more selectively permissive environment than animal hosts, or both. Our results provide valuable data on the rates of genomic and phenotypic change in Wolbachia associated with host shifts over short time scales. © The Author(s) 2013. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
Keywords: Endosymbiont; Evolution; Genomics; Wolbachia
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Zaremski, A., Gastonguay, L., Zaremski, C., Chaffanel, F., Le Floch, G., & Beauchene, J. (2013). Capacity of tropical forest soils of french guiana and réunion for depolluting the woods impregnated with biocides. Bois Forets Tropiques, 67(318), 51–58.
Abstract: Wood material for a long time was treated with fungicides or insecticides whose impact on the soil after leaching constitutes a real environmental problem. Nowadays, most of the studies on degradation of these toxic products was carried out with microorganisms which have been isolated in the laboratory. The present study sought to refine the knowledge vis-à-vis these microorganisms, especially wood-destroying fungi degrading pollutants in situ, from which few data are actually available. To decontaminate treated wood, the capacity of wooddestroying microorganisms from tropical forest soils of French Guiana and Reunion was evaluated to degrade toxic biocides. These are pentachlorophenol (PCP) and copper- chromium arsenic based compounds (CCA). Monitoring the degradation of samples of red pine, Pinus resinosa, shows that soils of French Guiana are more efficient than those of Reunion Island in terms of microbial activity vis-àvis these two biocides. A significant difference in loss of mass in specimens of red pine treated with CCA and PCP can range from single to double (respectively 18% and 30%). These findings confirm that CCA is less leacher and less degradable than the PCP by microorganisms in the soil. According to the scale of mass loss in laboratory tests, the wood so treated would be classified very not durable after three years of contact with soil, while the treatment is expected to be very durable.
Keywords: Bioremediation; Copper chromium arsenic(CCA) wood-destroying fungi; Depollution; Loss of mass; Pentachlorophenol(PCP); Treated timber; Tropical soil
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Lefèvre, F., Boivin, T., Bontemps, A., Courbet, F., Davi, H., Durand-Gillmann, M., et al. (2013). Considering evolutionary processes in adaptive forestry. Ann For Sci, 71(7), 723–739.
Abstract: Context: Managing forests under climate change requires adaptation. The adaptive capacity of forest tree populations is huge but not limitless. Integrating evolutionary considerations into adaptive forestry practice will enhance the capacity of managed forests to respond to climate-driven changes.
Aims: Focusing on natural regeneration systems, we propose a general framework that can be used in various and complex local situations by forest managers, in combination with their own expertise, to integrate evolutionary considerations into decision making for the emergence of an evolution-oriented forestry.
Methods: We develop a simple process-based analytical grid, using few processes and parameters, to analyse the impact of forestry practice on the evolution and evolvability of tree populations.
Results: We review qualitative and, whenever possible, quantitative expectations on the intensity of evolutionary drivers in forest trees. Then, we review the effects of actual and potential forestry practice on the evolutionary processes. We illustrate the complexity of interactions in two study cases: the evolutionary consequences for forest trees of biotic interactions and of highly heterogeneous environment.
Conclusion: Evolution-oriented forestry may contribute adapting forests to climate change. It requires combining short-term and long-term objectives. We propose future lines of research and experimentation.
Keywords: Adaptation; Climate change; Evolution-oriented forest management; Genetic resources; Silviculture
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Zhang, T., Bai, S. L., Zhang, Y. F., & Thibaut, B. (2012). Viscoelastic properties of wood materials characterized by nanoindentation experiments. Wood Sci. Technol., 46(5), 1003–1016.
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Djenontin Tindo, S., Amusant, N., Dangou, J., Wotto, D. V., Avlessi, F., Dahouénon-Ahoussi, E., et al. (2012). Screening of Repellent, Termiticidal and Preventive activities on Wood, of Azadirachta indica and Carapa procera (Meliaceae) seeds oils. ISCA J. Biological Sci., 1(3), 25–29.
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Baraloto, C., Herault, B., Paine, C. E. T., Massot, H., Blanc, L., Bonal, D., et al. (2012). Contrasting taxonomic and functional responses of a tropical tree community to selective logging. J. Appl. Ecol., 49(4), 861–870.
Abstract: 1.Considerable debate surrounds the extent to which tropical forests can be managed for resource extraction while conserving biodiversity and ecosystem properties, which depend on functional composition. Here we evaluate the compatibility of these aims by examining the effects of logging on taxonomic and functional diversity and composition in a tropical forest. 2.Twenty years after selective logging, we inventoried 4140 stems regenerating in logging gaps and adjacent undisturbed areas, and we integrated a database of 13 functional traits describing leaf and wood economics of tropical trees. 3.We found no differences in taxonomic and functional richness among habitats, but logging gaps had significantly higher taxonomic and functional evenness. 4.Logging also effected striking, long-term changes in both species and functional composition. In particular, the xylem density of recruits in logging gaps was 6% less than in unlogged forests, leaves were 11% less tough and had 6-13% greater mineral nutrient concentrations. 5.Synthesis and applications. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand. © 2012 The Authors. Journal of Applied Ecology © 2012 British Ecological Society.
Keywords: Canopy gap dynamics; Disturbance; French Guiana; Functional diversity; Functional evenness; Functional traits; Light partitioning; Species richness; Tropical rain forest
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Paine, C. E. T., Norden, N., Chave, J., Forget, P. - M., Fortunel, C., Dexter, K. G., et al. (2012). Phylogenetic density dependence and environmental filtering predict seedling mortality in a tropical forest. Ecol. Lett., 15(1), 34–41.
Abstract: Negative density dependence (NDD) and environmental filtering (EF) shape community assembly, but their relative importance is poorly understood. Recent studies have shown that seedling's mortality risk is positively related to the phylogenetic relatedness of neighbours. However, natural enemies, whose depredations often cause NDD, respond to functional traits of hosts rather than phylogenetic relatedness per se. To understand the roles of NDD and EF in community assembly, we assessed the effects on seedling mortality of functional similarity, phylogenetic relatedness and stem density of neighbouring seedlings and adults in a species-rich tropical forest. Mortality risks increased for common species when their functional traits departed substantially from the neighbourhood mean, and for all species when surrounded by close relatives. This indicates that NDD affects community assembly more broadly than does EF, and leads to the tentative conclusion that natural enemies respond to phylogenetically correlated traits. Our results affirm the prominence of NDD in structuring species-rich communities. © 2011 Blackwell Publishing Ltd/CNRS.
Keywords: Community assembly; Density dependence; French Guiana; Generalised linear mixed models; Janzen-Connell hypothesis; Seedling recruitment; Species coexistence; Survival
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Bordenave, B., Lehir, F., & Lorans, M. (2012). Current knowledge on threatened plant species of French Guiana. Rev. Ecol. Terre Vie, 67(Suppl.2), 29–45.
Abstract: The elaboration of a first list of the most threatened species of the overseas territory of French Guyana was undertaken in 2009 by the Association for Botanical Conservation in French Guiana in collaboration with the National Botanical Conservatory of Brest. Carried out in synergy with the updating of the species list for Natural Areas of Ecological, Faunistic and Floritic Interests supervised by the Region Science Council for Natural Heritage, this work includes 97 vascular plants, 18 of which can be considered as threatened in the state of current knowledge, according to the IUCN criteria which are recommended by the Federation of National Botanical Conservatories. Among these 18 taxa, threatened because of their rarity and the fragility of their natural habitats, 17 are already protected by a 2001 ministry decree and one is from a new genus, Hekkingia bordenavei; nine of these appear to be of high concern for conservation: Cleistes grandifiora (Orchidaceae), Cornutia pubescens (Verbenaceae), Antirhea triflora (Rubiaceae), Himathantus drasticus (Apocynaceae), Axonopus oiapocensis (Poaceae), Psychotria granvillei (Rubiaceae), Eriocaulon guyanense (Eriocaulaceae) along with two palm species subject to National Action Plans for their conservation since 2009, Astrocaryum minus and Bactris nancibaensis. This study also contributes to the on-going “regional Red List” of the French Guiana flora.
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