Baudrimont, M., Arini, A., Guégan, C., Venel, Z., Gigault, J., Pedrono, B., et al. (2020). Ecotoxicity of polyethylene nanoplastics from the North Atlantic oceanic gyre on freshwater and marine organisms (microalgae and filter-feeding bivalves). Environ. Sci. Pollut. Res., 27(4), 3746–3755.
Abstract: Each year, 5 to 10 million tons of plastic waste is dumped in the oceans via freshwaters and accumulated in huge oceanic gyres. Under the effect of several abiotic factors, macro plastic wastes (or plastic wastes with macro sizes) are fractionated into microplastics (MP) and finally reach the nanometric size (nanoplastic NP). To reveal potential toxic impacts of these NPs, two microalgae, Scenedemus subspicatus (freshwater green algae), and Thalassiosira weissiflogii (marine diatom) were exposed for up to 48 h at 1, 10, 100, 1000, and 10,000 μg/L to reference polyethylene NPs (PER) or NPs made from polyethylene collected in the North Atlantic gyre (PEN, 7th continent expedition in 2015). Freshwater filter-feeding bivalves, Corbicula fluminea, were exposed to 1000 μg/L of PER and PEN for 48 h to study a possible modification of their filtration or digestion capacity. The results show that PER and PEN do not influence the cell growth of T. weissiflogii, but the PEN exposure causes growth inhibition of S. subspicatus for all exposure concentrations tested. This growth inhibition is enhanced for a higher concentration of PER or PEN (10,000 μg/L) in S. subspicatus. The marine diatom T. weissiflogii appears to be less impacted by plastic pollution than the green algae S. subspicatus for the exposure time. Exposure to NPs does not lead to any alteration of bivalve filtration; however, fecal and pseudo-fecal production increased after PEN exposure, suggesting the implementation of rejection mechanisms for inedible particles. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
Keywords: Cordicula fluminea; Ecotoxicity; Nanoplastics; Polyethylene; Scenedesmus subspicatus; Thalassiosira weissiflogii; bivalve; concentration (composition); ecotoxicology; filter feeder; gyre; microalga; nanoparticle; plastic waste; pollution exposure; polymer; Atlantic Ocean; Atlantic Ocean (North); Bivalvia; Chlorophyta; Corbicula fluminea; Desmodesmus subspicatus; Nitzschia alba; Thalassiosira
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Scotti, I., Gugerli, F., Pastorelli, R., Sebastiani, F., & Vendramin, G. G. (2008). Maternally and paternally inherited molecular markers elucidate population patterns and inferred dispersal processes on a small scale within a subalpine stand of Norway spruce (Picea abies [L.] Karst.). For. Ecol. Manage., 255(11), 3806–3812.
Abstract: The within-population spatial structure of genetic diversity is shaped by demographic processes, including historical accidents such as forest perturbations. Information drawn from the analysis of the spatial distribution of genetic diversity is therefore inherently linked to demographic-historical processes that ultimately determine the fate of populations. All adult trees and saplings in a 1.4-ha plot within a mixed Norway spruce (Picea abies [L.] Karst) stand were characterised by means of chloroplast (paternally inherited) markers, and a large sub-sample of these were genotyped at mitochondrial (maternally inherited) molecular markers. These data were used to analyse the spatial distribution of genetic variation and to compare the patterns corresponding to the two marker types. The plot presented non-homogeneous local stem density in the younger cohorts, and the indirect effect of this source of variation on the spatial genetic structure was investigated. Results suggest that (i) spatially limited seed dispersal induced patchiness in genotype distribution, while pollen flow had a homogenising effect; (ii) deviations from random spatial structure were stronger in the demographically most stable portions of the stand, while they were weaker where sudden bursts of regeneration occurred; (iii) spatially overlapping adult and sapling cohorts displayed the same spatial genetic structure (stronger on stable areas, weaker in portions of the stand undergoing events of intense regeneration), which was substantiated by the influence of local demographic processes. Regeneration dynamics as modulated by demography thus influences the distribution of genetic diversity within the stand both in the younger life stages and in the adult population. (C) 2008 Elsevier B.V. All rights reserved.
Keywords: chloroplast microsatellites; mitochondrial minisatellites; pollen/seed dispersal; demography; spatial autocorrelation
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Lebrini, M., Roos, C., Vezin, H., & Robert, F. (2011). Electrochemical and theoretical studies of adsorption of some indole derivates at C38 Steel/Sulfuric acid interface as corrosion inhibitors. Int.J.Electrochem.Sci., 6(9), 3844–3857.
Abstract: The inhibitive action of 9H-pyrido[3,4-b]indole (norharmane) and 1-Methyl-9H-pyrido[3,4-b]indole (harmane) on corrosion of C38 steel in 0.5 M H2SO4 solution was investigated through electrochemical techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution for all concentrations studied. Polarization measurements indicate that the examined compounds act as a mixed inhibitor and its inhibition efficiency increases with inhibitor concentration. Data obtained from ac impedance technique show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE), has been used. The adsorption of used compounds on the steel surface obeys Langmuir's isotherm. The ΔG°ads values were calculated and discussed for both inhibitors. Significant correlations are obtained between inhibition efficiency and quantum chemical parameters using quantitative structure-activity relationship (QSAR) method. © 2011 by ESG.
Keywords: Acidic media; Adsorption; C38 steel; Corrosion inhibitors; Theoretical calculations
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Guitet, S., Sabatier, D., Brunaux, O., Couteron, P., Denis, T., Freycon, V., et al. (2018). Disturbance Regimes Drive the Diversity of Regional Floristic Pools Across Guianan Rainforest Landscapes. Sci. Rep., 8, 3872.
Abstract: Disturbances control rainforest dynamics, and, according to the intermediate disturbance hypothesis (IDH), disturbance regime is a key driver of local diversity. Variations in disturbance regimes and their consequences on regional diversity at broad spatiotemporal scales are still poorly understood. Using multidisciplinary large-scale inventories and LiDAR acquisitions, we developed a robust indicator of disturbance regimes based on the frequency of a few early successional and widely distributed pioneer species. We demonstrate at the landscape scale that tree-species diversity and disturbance regimes vary with climate and relief. Significant relationships between the disturbance indicator, tree-species diversity and soil phosphorus content agree with the hypothesis that rainforest diversity is controlled both by disturbance regimes and long-term ecosystem stability. These effects explain the broad-scale patterns of floristic diversity observed between landscapes. In fact, species-rich forests in highlands, which have benefited from long-term stability combined with a moderate and regular regime of local disturbances, contrast with less diversified forests on recently shaped lowlands, which have undergone more recent changes and irregular dynamics. These results suggest that taking the current disturbance regime into account and including geomorphological stratifications in climate-vegetation models may be an effective way to improve the prediction of changes in species diversity under climate change. © 2018 The Author(s).
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Aubry-Kientz, M., Laybros, A., Weinstein, B., Ball, J. G. C., Jackson, T., Coomes, D., et al. (2021). Multisensor data fusion for improved segmentation of individual tree crowns in dense tropical forests. IEEE Journal of Selected topics in Applied Earth Observations and Remote Sensing, 14, 3927–3936.
Abstract: Automatic tree crown segmentation from remote sensing data is especially challenging in dense, diverse, and multilayered tropical forest canopies, and tracking mortality by this approach is even more difficult. Here, we examine the potential for combining airborne laser scanning (ALS) with multispectral and hyperspectral data to improve the accuracy of tree crown segmentation at a study site in French Guiana. We combined an ALS point cloud clustering method with a spectral deep learning model to achieve 83% accuracy at recognizing manually segmented reference crowns (with congruence >0.5). This method outperformed a two-step process that involved clustering the ALS point cloud and then using the logistic regression of hyperspectral distances to correct oversegmentation. We used this approach to map tree mortality from repeat surveys and show that the number of crowns identified in the first that intersected with height loss clusters was a good estimator of the number of dead trees in these areas. Our results demonstrate that multisensor data fusion improves the automatic segmentation of individual tree crowns and presents a promising avenue to study forest demography with repeated remote sensing acquisitions.
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Coste, S., Roggy, J. C., Schimann, H., Epron, D., & Dreyer, E. (2011). A cost-benefit analysis of acclimation to low irradiance in tropical rainforest tree seedlings: leaf life span and payback time for leaf deployment. J. Exp. Bot., 62(11), 3941–3955.
Abstract: The maintenance in the long run of a positive carbon balance under very low irradiance is a prerequisite for survival of tree seedlings below the canopy or in small gaps in a tropical rainforest. To provide a quantitative basis for this assumption, experiments were carried out to determine whether construction cost (CC) and payback time for leaves and support structures, as well as leaf life span (i) differ among species and (ii) display an irradiance-elicited plasticity. Experiments were also conducted to determine whether leaf life span correlates to CC and payback time and is close to the optimal longevity derived from an optimization model. Saplings from 13 tropical tree species were grown under three levels of irradiance. Specific-CC was computed, as well as CC scaled to leaf area at the metamer level. Photosynthesis was recorded over the leaf life span. Payback time was derived from CC and a simple photosynthesis model. Specific-CC displayed only little interspecific variability and irradiance-elicited plasticity, in contrast to CC scaled to leaf area. Leaf life span ranged from 4 months to > 26 months among species, and was longest in seedlings grown under lowest irradiance. It was always much longer than payback time, even under the lowest irradiance. Leaves were shed when their photosynthesis had reached very low values, in contrast to what was predicted by an optimality model. The species ranking for the different traits was stable across irradiance treatments. The two pioneer species always displayed the smallest CC, leaf life span, and payback time. All species displayed a similar large irradiance-elicited plasticity.
Keywords: Carbon balance; construction cost; functional diversity; leaf life span; payback time; photosynthesis; tropical rainforest
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Faustin, M., Lebrini, M., Robert, F., & Roos, C. (2011). Corrosion studies of C38 steel by alkaloids extract of a tropical plant type. Int.J.Electrochem.Sci., 6(9), 4095–4113.
Abstract: Alkaloids extract of Aspidosperma album was tested as corrosion inhibitor for C38 steel in 1 M HCl by using polarization and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization curves indicated that the plant extract behaves as mixed-type inhibitors. Impedance measurements showed that the double-layer capacitance decreased and charge-transfer resistance increased with increase in the inhibitors concentration and hence increasing in inhibition efficiency. The effect of temperature on the corrosion behavior of C38 steel in 1 M HCl with and without addition of plant extract was studied in the temperature range 25 – 55°C. The adsorption of the inhibitor molecules was in accordance with the Langmuir adsorption isotherm. The results obtained show that this plant extract could serve as an effective inhibitor for the corrosion of C38 steel in hydrochloric acid. © 2011 by ESG.
Keywords: Acidic media; C38 steel; Corrosion inhibitor; Plant extract
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Christensen-Dalsgaard, K. K., Ennos, A. R., & Fournier, M. (2007). Changes in hydraulic conductivity, mechanical properties, and density reflecting the fall in strain along the lateral roots of two species of tropical trees. J. Exp. Bot., 58(15-16), 4095–4105.
Abstract: Roots have been described as having larger vessels and so greater hydraulic efficiency than the stem. Differences in the strength and stiffness of the tissue within the root system itself are thought to be an adaptation to the loading conditions experienced by the roots and to be related to differences in density. It is not known how potential mechanical adaptations may affect the hydraulic properties of the roots. The change in strength, stiffness, conductivity, density, sapwood area, and second moment of area distally along the lateral roots of two tropical tree species in which the strain is known to decrease rapidly was studied and the values were compared with those of the trunk. It was found that as the strain fell distally along the roots, so did the strength and stiffness of the tissue, whereas the conductivity increased exponentially. These changes appeared to be related to differences in density. In contrast to the distal-most roots, the tissue of the proximal roots had a lower conductivity and higher strength than that of the trunk. This suggests that mechanical requirements on the structure rather than the water potential gradient from roots to branches are responsible for the general pattern that roots have larger vessels than the stem. In spite of their increased transectional area, the buttressed proximal roots were subjected to higher levels of stress and had a lower total conductivity than the rest of the root system. © 2007 The Author(s).
Keywords: Buttress roots; Density; Hydraulic conductivity; Hydraulic-mechanical trade-offs; Modulus of elasticity; Tropical trees; Wood; Elastic moduli; Hydraulic conductivity; Wood; Buttress roots; Hydraulic-mechanical trade-offs; Tropical trees; Forestry; water; article; biomechanics; histology; legume; physiology; plant root; plant stem; tree; wood; Xylopia; Biomechanics; Fabaceae; Plant Roots; Plant Stems; Trees; Water; Wood; Xylopia; Conductivity; Elastic Strength; Forestry; Wood
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Lambs, L., Bompy, F., Imbert, D., Corenblit, D., & Dulormne, M. (2015). Seawater and freshwater circulations through coastal forested wetlands on a Caribbean Island. Water, 7(8), 4108–4128.
Abstract: Structure and composition of coastal forested wetlands are mainly controlled by local topography and soil salinity. Hydrology plays a major role in relation with tides, seaward, and freshwater inputs, landward. We report here the results of a two-year study undertaken in a coastal plain of the Guadeloupe archipelago (FWI). As elsewhere in the Caribbean islands, the study area is characterized by a micro-tidal regime and a highly seasonal climate. This work aimed at understanding groundwater dynamics and origin (seawater/freshwater) both at ecosystems and stand levels. These hydrological processes were assessed through 18O/16O and 2H/1H isotopic analyses, and from monthly monitoring of water level and soil salinity at five study sites located in mangrove (3) and swamp forest (2). Our results highlight the importance of freshwater budget imbalance during low rainfall periods. Sustained and/or delayed dry seasons cause soil salinity to rise at the mangrove/swamp forest ecotone. As current models on climate change project decreasing rainfall amounts over the inner Caribbean region, one may expect for this area an inland progression of the mangrove forest to the expense of the nearby swamp forest. © 2015 by the authors.
Keywords: 18O/2H stable isotope; Hydrology; Mangrove; Salinity; Swamp forest; Water level
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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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