Li, M. C., Royer, M., Stien, D., Lecante, A., & Roos, C. (2008). Inhibitive effect of sodium eperuate on zinc corrosion in alkaline solutions. Corrosion Sci., 50(7), 1975–1981.
Abstract: The effect of sodium eperuate prepared from Wallaba (Eperua falcata Aubl) extract on zinc corrosion was investigated in alkaline solutions with chloride ions (i.e., simulated concrete pore solutions) by using electrochemical techniques. Sodium eperuate inhibits the corrosion of zinc in 0.1 M NaCl solutions with pH 9.6. As its concentration increases to 1 g/L, the inhibition efficiency reaches approximately 92%. In alkaline solutions with pH 12.6, sodium eperuate has no adverse effect on passivity of zinc, and retards the chloride attack. These suggest that sodium eperuate is an effective inhibitor for the protection of zinc in alkaline environments. (c) 2008 Elsevier Ltd. All rights reserved.
Keywords: zinc; concrete; EIS; alkaline corrosion; passivity
|
Clair, B., Arinero, R., Leveque, G., Ramonda, M., & Thibaut, B. (2003). Imaging the mechanical properties of wood cell wall layers by atomic force modulation microscopy. IAWA J., 24(3), 223–230.
Abstract: Atomic Force Microscopy in force modulation mode was used to study the elastic properties of the different fibre wall layers of the tension wood of holm oak and normal wood of boco. The method is based on the measurement of the resonance frequency of the microscope lever in contact with the sample. This frequency is related to the reduced Young modulus E* = E/(1-nu(2)) of the material, supposed to be isotropic. 'Elastic' images of the cell are obtained simultaneously with the topographic images, which allows the observation of the mechanical properties of the cells at a nanometric scale. Layers G, S-1, S-2 and ML can clearly be distinguished. By comparison with known materials an estimation of the absolute modulus is given in the range 5-20 GPa, but should be considered with caution, because the inherent anisotropy of the materials has not been taken into account.
Keywords: wood; cell wall; mechanical properties; elastic modulus; tension wood
|
Christensen-Dalsgaard, K. K., Ennos, A. R., & Fournier, M. (2008). Are radial changes in vascular anatomy mechanically induced or an ageing process? Evidence from observations on buttressed tree root systems. Trees-Struct. Funct., 22(4), 543–550.
Abstract: To investigate the effect of changes in mechanical loading conditions on radial anatomical patterns, we here compare the trunk with the roots in two locations of three species of buttressed trees. The proximal part of the buttress roots is highly mechanically loaded throughout juvenile growth whereas the distal part of the buttresses is though to be mechanically unimportant at formation but become progressively more mechanically loaded during growth. We measured the frequency and diameter of the vessels and the vessel area fraction, and from this calculated the specific conductivity of tissue samples of the core-, intermediate- and outer wood. As in previous studies there was an increase in vessel size, vessel area fraction and specific conductivity from the pith to the bark in the trunk. In the proximal part of the buttress roots, however, there was no increase in vessel size and conductivity from core wood and out in agreement with the high mechanical loading found here throughout growth. There was instead a decrease in vessel size, vessel area fraction and specific conductivity from core- to outer wood in the distal part of the buttress roots in accordance with the increase in mechanical loading. Hence, it appears that the radial anatomical patterns are not a passive function of cambial ageing but may be modified in response to local mechanical loading.
Keywords: wood; anatomy; mechanical loading; tree development; vessels
|
Hénaut, Y., Corbara, B., Azémar, F., Céréghino, R., Dézerald, O., & Dejean, A. (2018). An arboreal spider protects its offspring by diving into the water of tank bromeliads. Comptes Rendus Biologies, 341(3), 196–199.
Abstract: Cupiennius salei (Ctenidae) individuals frequently live in association with tank bromeliads, including Aechmea bracteata, in Quintana Roo (Mexico). Whereas C. salei females without egg sacs hunt over their entire host plant, females carrying egg sacs settle above the A. bracteata reservoirs they have partially sealed with silk. There they avoid predators that use sight to detect their prey, as is known for many bird species. Furthermore, if a danger is more acute, these females dive with their egg sacs into the bromeliad reservoir. An experiment showed that this is not the case for males or females without egg sacs. In addition to the likely abundance of prey found therein, the potential of diving into the tank to protect offspring may explain the close association of this spider with bromeliads. These results show that, although arboreal, C. salei evolved a protective behavior using the water of tank bromeliads to protect offspring. Résumé L’araignée Cupiennius salei (Ctenidae) vit souvent en association avec la broméliacée à réservoir Aechmea bracteata. Dans le Quintana Roo (Mexique), les femelles qui transportent un cocon s’installent au-dessus d’un réservoir d’A. bracteata qu’elles obstruent partiellement de voiles de soie pour se camoufler des prédateurs. En présence de vibrations importantes et répétées, ces femelles plongent avec leur cocon dans l’eau du réservoir. Notre étude montre que les autres adultes (mâles et femelles sans cocon) n’utilisent pas les réservoirs d’eau. Ainsi, en plus de l’abondance de proies, la possibilité de pouvoir plonger pour protéger la descendance pourrait expliquer l’association entre cette espèce d’araignée et les broméliacées. Nos expériences montrent que les femelles porteuses d’un cocon manifestent une stratégie de protection vis-à-vis des cocons et d’elles-mêmes en s’immergeant durant 30, voire 90minutes.
Keywords: Water used in protective behavior; Egg sacs; ; ; Cocons; Eau utilisée dans un comportement protecteur
|
Wagner, F., Herault, B., Stahl, C., Bonal, D., & Rossi, V. (2011). Modeling water availability for trees in tropical forests. Agric. For. Meteorol., 151(9), 1202–1213.
Abstract: Modeling soil water availability for tropical trees is a prerequisite to predicting the future impact of climate change on tropical forests. In this paper we develop a discrete-time deterministic water balance model adapted to tropical rainforest climates, and we validate it on a large dataset that includes micrometeorological and soil parameters along a topographic gradient in a lowland forest of French Guiana. The model computes daily water fluxes (rainfall interception, drainage, tree transpiration and soil plus understorey evapotranspiration) and soil water content using three input variables: daily precipitation, potential evapotranspiration and solar radiation. A novel statistical approach is employed that uses Time Domain Reflectometer (TDR) soil moisture data to estimate water content at permanent wilting point and at field capacity, and root distribution. Inaccuracy of the TDR probes and other sources of uncertainty are taken into account by model calibration through a Bayesian framework. Model daily output includes relative extractable water, REW, i.e. the daily available water standardized by potential available water. The model succeeds in capturing temporal variations in REW regardless of topographic context. The low Root Mean Square Error of Predictions suggests that the model captures the most important drivers of soil water dynamics, i.e. water refilling and root water extraction. Our model thus provides a useful tool to explore the response of tropical forests to climate scenarios of changing rainfall regime and intensity. (C) 2011 Elsevier B.V. All rights reserved.
Keywords: Water balance model; Amazonian rainforest; Time domain reflectometer; Bayesian inference; Tree drought stress
|
Courtois, E. A., Paine, C. E. T., Blandinieres, P. A., Stien, D., Bessiere, J. M., Houel, E., et al. (2009). Diversity of the Volatile Organic Compounds Emitted by 55 Species of Tropical Trees: a Survey in French Guiana. J. Chem. Ecol., 35(11), 1349–1362.
Abstract: Volatile organic compounds (VOCs) are produced by a broad range of organisms, from bacteria to mammals, and they represent a vast chemical diversity. In plants, one of the preeminent roles of VOCs is their repellent or cytotoxic activity, which helps the plant deter its predators. Most studies on VOCs emitted by vegetative parts have been conducted in model plant species, and little is known about patterns of VOC emissions in diverse plant communities. We conducted a survey of the VOCs released immediately after mechanical damage of the bark and the leaves of 195 individual trees belonging to 55 tropical tree species in a lowland rainforest of French Guiana. We discovered a remarkably high chemical diversity, with 264 distinct VOCs and a mean of 37 compounds per species. Two monoterpenes (alpha-pinene and limonene) and two sesquiterpenes (beta-caryophyllene and alpha-copaene), which are known to have cytotoxic and deterrent effects, were the most frequent compounds in the sampled species. As has been established for floral scents, the blend of VOCs is largely species-specific and could be used to discriminate among 43 of the 55 sampled species. The species with the most diverse blends were found in the Sapindales, Laurales, and Magnoliales, indicating that VOC diversity is not uniformly distributed among tropical species. Interspecific variation in chemical diversity was caused mostly by variation in sesquiterpenes. This study emphasizes three aspects of VOC emission by tropical tree species: the species-specificity of the mixtures, the importance of sesquiterpenes, and the wide-ranging complexity of the mixtures.
Keywords: VOCs; Chemical diversity; Sesquiterpenes; Tropical; French Guiana
|
Dejean, A., Carpenter, J. M., Gibernau, M., Leponce, M., & Corbara, B. (2010). Nest relocation and high mortality rate in a Neotropical social wasp: Impact of an exceptionally rainy La Nina year. C. R. Biol., 333(1), 35–40.
Abstract: After noting the forecast of a La Nina episode, associated with heavy rainfall in French Guiana, we monitored the fate of wasp nests before and during the 2006 short rainy season. The population of the most abundant epiponine wasp species, Polybia bistriata, decreased dramatically during the short rainy season (60.6% of the nests disappeared) then remained low for at least 18 months. Colonies that survived moved from the shelter of large, low leaves (a situation well adapted to the previous dry season) of the most frequent substrate tree, Clusia grandiflora (Clusiaceae), to upper leaves, better ventilated and whose orientation provides good protection from the rain. Therefore, the possibility of moving the nest higher during the first rains following the dry season seems very adaptive as colonies that do not do so are eliminated during the La Nina years, whose frequency will increase with global climate change. (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Vespidae; Population size variation; Microevolution; La Nina; French Guiana
|
Scotti-Saintagne, C., Bertocchi, E., Barreneche, T., Kremer, A., & Plomion, C. (2005). Quantitative trait loci mapping for vegetative propagation in pedunculate oak. Ann. For. Sci., 62(4), 369–374.
Abstract: Vegetative propagation is one of the main methods used for the deployment of improved genetic forest tree species. The objective of this paper was to study the genetic architecture of vegetative propagation by detecting Quantitative Trait Loci (QTL) in pedunculate oak ( Quercus robur). The mapping population consisted on an F-1 family of 278 offspring. Assessment of rooting ability over three years permitted the detection of 10 QTLs explaining between 4.4 and 13.8% of phenotypic variance, of which the two strongest were stable across years. Ongoing genomics programs in trees and in Arabidopsis are starting to shed light on the nature of the underlying genes.
Keywords: vegetative propagation; QTL; Quercus robur
|
Lamarre, G. P. A., Amoretti, D. S., Baraloto, C., Bénéluz, F., Mesones, I., & Fine, P. V. A. (2016). Phylogenetic Overdispersion in Lepidoptera Communities of Amazonian White-sand Forests. Biotropica, 48(1), 101–109.
Abstract: In the Amazon basin and the Guiana Shield, white-sand (WS) forests are recognized as a low-resource habitat often composed by a distinct flora with many edaphic endemic plants. Small patches of nutrient-poor white-sand forests can pose a series of challenges to plants and animals. For plants, these challenges have been shown to function as strong filters that in turn drive taxonomic, functional and phylogenetic plant composition. However, very little is known about animal communities in WS forest and the effect that low-resource availability may have on higher trophic levels. Here, we investigate the diversity of both taxonomic and phylogenetic diversity of three Lepidoptera families' (Nymphalidae, Saturniidae, and Sphingidae) assemblages between low-resource (White-Sand Forest) and two adjacent high-resource habitats, terra firme clay and seasonally flooded forests. We found no clear effect of habitat type on taxonomic composition although butterfly and moth species abundance differed among the three contrasted habitats. The WS forest Lepidoptera community is significantly more phylogenetically overdispersed than expected by chance. We suggest that these low-resource habitats filter the number of plant lineages which, in turn, creates a bottom-up control structuring Lepidoptera phylogenetic structure. We recommend long-term sampling on Lepidoptera community both at larval and adult stages that may complement this study and test hypotheses linking herbivore phylogenetic structure to plant resource availability and trophic cascade theory. © 2016 The Association for Tropical Biology and Conservation.
Keywords: varillales; Amazon basin; Bottom-up; Lepidoptera composition; Moth, Nymphalidae; Phylogenetic structure
|
McLean, J. P., Zhang, T., Bardet, S., Beauchene, J., Thibaut, A., Clair, B., et al. (2011). The decreasing radial wood stiffness pattern of some tropical trees growing in the primary forest is reversed and increases when they are grown in a plantation. Ann. For. Sci., 68(4), 681–688.
Abstract: Background This study examines the radial trend in wood stiffness of tropical rainforest trees. The objective was to determine if the type of growing environment (exposed plantation or dense primary forest) would have an effect on this radial trend. Methods The axial elastic modulus of wood samples, representing a pith to bark cross-section, of six trees from several French Guianese species (two of Eperua falcata, one of Eperua grandiflora, two of Carapa procera and one of Symphonia gloubulifera) was measured using a dynamic “forced vibration” method. Results Primary forest trees were observed to have a decrease in wood stiffness from pith to bark, whereas plantation trees, from the same genus or species, displayed a corresponding increase in wood stiffness. Juvenile wood stiffness appears to vary depending on the environment in which the tree had grown. Conclusion We suggest that the growth strategy of primary forest trees is to produce wood resistant to self-buckling so that the height of the canopy may be obtained with the maximum of efficiency. In contrast, the growth strategy of the trees growing in an exposed plantation is to produce low-stiffness wood, important to provide flexibility in wind. Further experiments to study the behaviour of more species, with more individuals per species, growing across a range of physical environments, are required.
Keywords: Tropical trees; Growth strategy; Wood stiffness; Juvenile wood
|
