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Cachet, N.; Hoakwie, F.; Bertani, S.; Bourdy, G.; Deharo, E.; Stien, D.; Houel, E.; Gornitzka, H.; Fillaux, J.; Chevalley, S.; Valentin, A.; Jullian, V. |
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Title |
Antimalarial Activity of Simalikalactone E, a New Quassinoid from Quassia amara L. (Simaroubaceae) |
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Journal Article |
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2009 |
Publication |
Antimicrobial Agents and Chemotherapy |
Abbreviated Journal |
Antimicrob. Agents Chemother. |
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53 |
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10 |
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4393-4398 |
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We report the isolation and identification of a new quassinoid named simalikalactone E (SkE), extracted from a widely used Amazonian antimalarial remedy made out of Quassia amara L. (Simaroubaceae) leaves. This new molecule inhibited the growth of Plasmodium falciparum cultured in vitro by 50%, in the concentration range from 24 to 68 nM, independently of the strain sensitivity to chloroquine. We also showed that this compound was able to decrease gametocytemia with a 50% inhibitory concentration sevenfold lower than that of primaquine. SkE was found to be less toxic than simalikalactone D (SkD), another antimalarial quassinoid from Q. amara, and its cytotoxicity on mammalian cells was dependent on the cell line, displaying a good selectivity index when tested on nontumorogenic cells. In vivo, SkE inhibited murine malaria growth of Plasmodium vinckei petteri by 50% at 1 and 0.5 mg/kg of body weight/day, by the oral or intraperitoneal routes, respectively. The contribution of quassinoids as a source of antimalarial molecules needs therefore to be reconsidered. |
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[Cachet, N.; Hoakwie, F.; Bourdy, G.; Deharo, E.; Chevalley, S.; Valentin, A.; Jullian, V.] Univ Toulouse, UPS, Lab Pharmacochim Subst Nat & Pharmacophores Redox, UMR 152, F-31062 Toulouse 9, France, Email: jullian@cict.fr |
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AMER SOC MICROBIOLOGY |
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0066-4804 |
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ISI:000270020600047 |
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EcoFoG @ eric.marcon @ |
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103 |
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Yamamoto, H.; Almeras, T. |
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A mathematical verification of the reinforced-matrix hypothesis using the Mori-Tanaka theory |
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Journal Article |
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2007 |
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Journal of Wood Science |
Abbreviated Journal |
J. Wood Sci. |
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53 |
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6 |
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505-509 |
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Engineering |
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This article presents a theoretical verification of the reinforced-matrix hypothesis derived from tensor equations, σ W = σ f + σ m and ε W = ε f = ε m (Wood Sci Technol 32:171–182, 1998; Wood Sci Technol 33:311–325, 1999; J Biomech Eng 124:432–440, 2002), using classical Mori-Tanaka theory on the micromechanics of fiber-reinforced materials (Acta Metall 21:571–574, 1973; Micromechanics — dislcation and inclusions (in Japanese), pp 141–147, 1976). The Mori-Tanaka theory was applied to a small fragment of the cell wall undergoing changes in its physical state, such as those arising from sorption of moisture, maturation of wall components, or action of an external force, to obtain ⟨σ A⟩D = ϕ·⟨σ F⟩I + (1−ϕ)·⟨σ M⟩D−I. When the constitutive equation of each constituent material was applied to the equation ⟨σ A⟩D = ϕ·⟨σ F⟩I + (1−ϕ)·⟨σ M⟩D−I, the equations σ W = σ f + σ m and ε W = ε f = ε m were derived to lend support to the concept that two main phases, the reinforcing cellulose microfibril and the lignin-hemicellulose matrix, coexist in the same domain. The constitutive equations for the cell wall fragment were obtained without recourse to additional parameters such as Eshelby’s tensor S and Hill’s averaged concentration tensors AF and AM. In our previous articles, the coexistence of two main phases and σ W = σ f + σ m and ε W = ε f =ε m had been taken as our starting point to formulate the behavior of wood fiber with multilayered cell walls. The present article provides a rational explanation for both concepts. |
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Springer Japan |
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1435-0211 |
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EcoFoG @ eric.marcon @ |
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215 |
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Lebrini, M.; Robert, F.; Lecante, A.; Roos, C. |
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Corrosion inhibition of C38 steel in 1 M hydrochloric acid medium by alkaloids extract from Oxandra asbeckii plant |
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Journal Article |
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2011 |
Publication |
Corrosion Science |
Abbreviated Journal |
Corrosion Sci. |
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53 |
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2 |
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687-695 |
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Steel; EIS; Polarization; Raman spectroscopy; Acid inhibition |
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The inhibition effect of alkaloids extract from Oxandra asbeckii plant (OAPE) on the corrosion of C38 steel in 1 M hydrochloric acid solution has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion inhibition efficiency increases on increasing plant extracts concentration. Cathodic and anodic polarization curves show that OAPE is a mixed-type inhibitor. 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 degrees C. The thermodynamic functions of dissolution and adsorption processes were calculated from experimental polarization data and the interpretation of the results are given. The adsorption of this plant extract on the C38 steel surface obeys the Langmuir adsorption isotherm. Surface analysis (Raman) was also carried out to establish the corrosion inhibitive property of this plant extract in HCl solution. (C) 2010 Elsevier Ltd. All rights reserved. |
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[Robert, F.; Lecante, A.; Roos, C.] UAG UMR ECOFOG, Lab Mat & Mol Milieu Amazonien, Cayenne 97337, French Guiana, Email: christophe.roos@guyane.univ-ag.fr |
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Pergamon-Elsevier Science Ltd |
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0010-938x |
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ISI:000287004700021 |
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EcoFoG @ webmaster @ |
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299 |
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Ruiz-González, M.X.; Lauth, J.; Leroy, C.; Jauneau, A.; Gryta, H.; Jargeat, P.; Dejean, A.; Orivel, J. |
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An efficient protocol for isolating melanised chaetothyrialean anamorphic fungi associated with plant-ants |
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Journal Article |
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2013 |
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Journal of Basic Microbiology |
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53 |
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1 |
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98-100 |
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Allomerus ants; Black fungi; Chaetothyriales; Fluorescent staining; Isolation method |
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Because of their ecological characteristics, slow growth rates and the presence of contaminants, Chaetothyriales fungi associated with structures built by tropical plant-ants can be difficult to isolate with standard procedures. Here, we describe an easy-to-use protocol for obtaining pure cultures by using cotton as a first substrate. We have further found by means of fluorescent stains that nuclei concentrate either in young hyphae or in the tips of the hyphae. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
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Université de Toulouse, ECOLAB, Toulouse, France |
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Export Date: 6 February 2013; Source: Scopus |
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EcoFoG @ webmaster @ |
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461 |
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Lebrini, M.; Robert, F.; Vezin, H.; Roos, C. |
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Electrochemical and quantum chemical studies of some indole derivatives as corrosion inhibitors for C38 steel in molar hydrochloric acid |
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Journal Article |
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2010 |
Publication |
Corrosion Science |
Abbreviated Journal |
Corrosion Sci. |
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52 |
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10 |
Pages |
3367-3376 |
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Steel; EIS; Raman spectroscopy; Polarization; Acid inhibition |
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A comparative study of 9H-pyrido[3,4-b]indole (norharmane) and 1-methyl-9H-pyrido[3,4-b]indole (harmane) as inhibitors for C38 steel corrosion in 1 M HCl solution at 25 degrees C was carried out. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were applied to study the metal corrosion behavior in the absence and presence of different concentrations of these inhibitors. The OCP as a function of time were also established. Cathodic and anodic polarization curves show that norharmane and harmane are a mixed-type inhibitors. Adsorption of indole derivatives on the C38 steel surface, in 1 M HCl solution, follows the Langmuir adsorption isotherm model. The Delta G degrees(ads) values were calculated and discussed. The potential of zero charge (PZC) of the C38 steel in inhibited solution was studied by the EIS method, and a mechanism for the adsorption process was proposed. Raman spectroscopy confirmed that indole molecules strongly adsorbed onto the steel surface. The electronic properties of indole derivates, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR). (C) 2010 Elsevier Ltd. All rights reserved. |
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[Robert, F.; Roos, C.] UAG UMR ECOFOG, Lab Mat & Mol Milieu Amazonien, Cayenne 97337, French Guiana, Email: christophe.roos@guyane.univ-ag.fr |
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PERGAMON-ELSEVIER SCIENCE LTD |
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0010-938X |
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ISI:000281315500026 |
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no |
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EcoFoG @ eric.marcon @ |
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44 |
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Almeras, T.; Yoshida, M.; Okuyama, T. |
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The generation of longitudinal maturation stress in wood is not dependent on diurnal changes in diameter of trunk |
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Journal Article |
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2006 |
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Journal of Wood Science |
Abbreviated Journal |
J. Wood Sci. |
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52 |
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5 |
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452-455 |
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maturation stress; growth stress; cell-wall maturation; continuous lighting; diurnal strains |
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A hypothetical mechanism for the generation of maturation stress in wood was tested experimentally. The hypothesis was that the maturation stress could partly originate in a physical mechanism related to daily changes in water pressure and associated diurnal strains. The matrix of lignin and hemicellulose, deposited in the cell wall during the night, would be put in compression by the effect of water tension during the next day. The cellulose framework, crystallizing during the day, would be put in tension by the decrease in tension at night and subsequent cell-wall swelling. This was tested on young saplings of sugi and beech. Half of the saplings were submitted to continuous lighting, which canceled diurnal strains. Saplings were tilted 40 degrees, and their uprighting movement was measured. The uprighting movement is directly due to the production of reaction wood and the concomitant development of large longitudinal maturation stress. It occurred in the continuously lighted plants at least as much as in control plants. We conclude that the generation of longitudinal maturation stress in tension or compression wood is not directly related to variations in water pressure and diurnal strains. |
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Nagoya Univ, Grad Sch Bioagr Sci, Lab Biomat Phys, Chikusa Ku, Nagoya, Aichi 4648601, Japan, Email: t_almeras@hotmail.com |
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SPRINGER TOKYO |
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1435-0211 |
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ISI:000241010600012 |
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EcoFoG @ eric.marcon @ |
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222 |
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Talaga, S.; Dejean, A.; Carinci, R.; Gaborit, P.; Dusfour, I.; Girod, R. |
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Updated Checklist of the Mosquitoes (Diptera: Culicidae) of French Guiana |
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Journal Article |
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2015 |
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Journal of Medical Entomology |
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Journal of Medical Entomology |
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52 |
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5 |
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770-782 |
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culicid; Neotropics; South America; species checklist; vector |
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The incredible mosquito species diversity in the Neotropics can provoke major confusion during vector control programs when precise identification is needed. This is especially true in French Guiana where studies on mosquito diversity practically ceased 35 yr ago. In order to fill this gap, we propose here an updated and comprehensive checklist of the mosquitoes of French Guiana, reflecting the latest changes in classification and geographical distribution and the recognition of current or erroneous synonymies. This work was undertaken in order to help ongoing and future research on mosquitoes in a broad range of disciplines such as ecology, biogeography, and medical entomology. Thirty-two valid species cited in older lists have been removed, and 24 species have been added including 12 species (comprising two new genera and three new subgenera) reported from French Guiana for the first time. New records are from collections conducted on various phytotelmata in French Guiana and include the following species: Onirion sp. cf Harbach and Peyton (2000), Sabethes (Peytonulus) hadrognathus Harbach, Sabethes (Peytonulus) paradoxus Harbach, Sabethes (Peytonulus) soperi Lane and Cerqueira, Sabethes (Sabethinus) idiogenes Harbach, Sabethes (Sabethes) quasicyaneus Peryassú , Runchomyia (Ctenogoeldia) magna (Theobald), Wyeomyia (Caenomyiella) sp. cf Harbach and Peyton (1990), Wyeomyia (Dendromyia) ypsipola Dyar, Wyeomyia (Hystatomyia) lamellata (Bonne-Wepster and Bonne), Wyeomyia (Miamyia) oblita (Lutz), and Toxorhynchites (Lynchiella) guadeloupensis (Dyar and Knab). At this time, the mosquitoes of French Guiana are represented by 235 species distributed across 22 genera, nine tribes, and two subfamilies. |
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UnitÉ d'Entomologie Médicale, Institut Pasteur de la Guyane, 23 Avenue Pasteur, Cayenne Cedex, France |
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Export Date: 22 October 2015 |
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EcoFoG @ webmaster @ |
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636 |
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Fayad, I.; Baghdadi, N.; Guitet, S.; Bailly, J.-S.; Herault, B.; Gond, V.; El Hajj, M.; Tong Minh, D.H. |
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Aboveground biomass mapping in French Guiana by combining remote sensing, forest inventories and environmental data |
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Journal Article |
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2016 |
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International Journal of Applied Earth Observation and Geoinformation |
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International Journal of Applied Earth Observation and Geoinformation |
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52 |
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502-514 |
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Aboveground biomass mapping; Forests; French Guiana; ICESat GLAS; LiDAR |
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Mapping forest aboveground biomass (AGB) has become an important task, particularly for the reporting of carbon stocks and changes. AGB can be mapped using synthetic aperture radar data (SAR) or passive optical data. However, these data are insensitive to high AGB levels (>150 Mg/ha, and >300 Mg/ha for P-band), which are commonly found in tropical forests. Studies have mapped the rough variations in AGB by combining optical and environmental data at regional and global scales. Nevertheless, these maps cannot represent local variations in AGB in tropical forests. In this paper, we hypothesize that the problem of misrepresenting local variations in AGB and AGB estimation with good precision occurs because of both methodological limits (signal saturation or dilution bias) and a lack of adequate calibration data in this range of AGB values. We test this hypothesis by developing a calibrated regression model to predict variations in high AGB values (mean >300 Mg/ha) in French Guiana by a methodological approach for spatial extrapolation with data from the optical geoscience laser altimeter system (GLAS), forest inventories, radar, optics, and environmental variables for spatial inter- and extrapolation. Given their higher point count, GLAS data allow a wider coverage of AGB values. We find that the metrics from GLAS footprints are correlated with field AGB estimations (R2 = 0.54, RMSE = 48.3 Mg/ha) with no bias for high values. First, predictive models, including remote-sensing, environmental variables and spatial correlation functions, allow us to obtain “wall-to-wall” AGB maps over French Guiana with an RMSE for the in situ AGB estimates of ∼50 Mg/ha and R2 = 0.66 at a 1-km grid size. We conclude that a calibrated regression model based on GLAS with dependent environmental data can produce good AGB predictions even for high AGB values if the calibration data fit the AGB range. We also demonstrate that small temporal and spatial mismatches between field data and GLAS footprints are not a problem for regional and global calibrated regression models because field data aim to predict large and deep tendencies in AGB variations from environmental gradients and do not aim to represent high but stochastic and temporally limited variations from forest dynamics. Thus, we advocate including a greater variety of data, even if less precise and shifted, to better represent high AGB values in global models and to improve the fitting of these models for high values. © 2016 Elsevier B.V. |
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NOVELTIS, 153 rue du Lac, Labège, France |
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Export Date: 9 December 2016 |
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EcoFoG @ webmaster @ |
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699 |
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Verryckt, L.T.; Ellsworth, D.S.; Vicca, S.; Van Langenhove, L.; Peñuelas, J.; Ciais, P.; Posada, J.M.; Stahl, C.; Coste, S.; Courtois, E.A.; Obersteiner, M.; Chave, J.; Janssens, I.A. |
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Can light-saturated photosynthesis in lowland tropical forests be estimated by one light level? |
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Journal Article |
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2020 |
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Biotropica |
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Biotropica |
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52 |
Issue |
6 |
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1183-1193 |
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canopy architecture; interspecific variation; light intensity; lowland environment; parameter estimation; photon flux density; photosynthesis; saturation; tropical forest; French Guiana |
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Leaf-level net photosynthesis (An) estimates and associated photosynthetic parameters are crucial for accurately parameterizing photosynthesis models. For tropical forests, such data are poorly available and collected at variable light conditions. To avoid over- or underestimation of modeled photosynthesis, it is critical to know at which photosynthetic photon flux density (PPFD) photosynthesis becomes light-saturated. We studied the dependence of An on PPFD in two tropical forests in French Guiana. We estimated the light saturation range, including the lowest PPFD level at which Asat (An at light saturation) is reached, as well as the PPFD range at which Asat remained unaltered. The light saturation range was derived from photosynthetic light-response curves, and within-canopy and interspecific differences were studied. We observed wide light saturation ranges of An. Light saturation ranges differed among canopy heights, but a PPFD level of 1,000 µmol m−2 s−1 was common across all heights, except for pioneer trees species that did not reach light saturation below 2,000 µmol m−2 s−1. A light intensity of 1,000 µmol m−2 s−1 sufficed for measuring Asat of climax species at our study sites, independent of the species or the canopy height. Because of the wide light saturation ranges, results from studies measuring Asat at higher PPFD levels (for upper canopy leaves up to 1,600 µmol m−2 s−1) are comparable with studies measuring at 1,000 µmol m−2 s−1. © 2020 The Association for Tropical Biology and Conservation |
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UMR 5174, Laboratoire Evolution et Diversité Biologique, CNRS, Université Paul Sabatier, Toulouse, France |
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Blackwell Publishing Ltd |
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00063606 (Issn) |
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EcoFoG @ webmaster @ |
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948 |
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Verryckt, L.T.; Van Langenhove, L.; Ciais, P.; Courtois, E.A.; Vicca, S.; Peñuelas, J.; Stahl, C.; Coste, S.; Ellsworth, D.S.; Posada, J.M.; Obersteiner, M.; Chave, J.; Janssens, I.A. |
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Coping with branch excision when measuring leaf net photosynthetic rates in a lowland tropical forest |
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Journal Article |
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2020 |
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Biotropica |
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Biotropica |
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52 |
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4 |
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608-615 |
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branch cutting; canopy physiology; French Guiana; gas exchange; photosynthesis; rainforest; stomatal conductance; ecological modeling; environmental conditions; forest canopy; leaf; measurement method; photosynthesis; tree; tropical forest; Gruidae |
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Measuring leaf gas exchange from canopy leaves is fundamental for our understanding of photosynthesis and for a realistic representation of carbon uptake in vegetation models. Since canopy leaves are often difficult to reach, especially in tropical forests with emergent trees up to 60 m at remote places, canopy access techniques such as canopy cranes or towers have facilitated photosynthetic measurements. These structures are expensive and therefore not very common. As an alternative, branches are often cut to enable leaf gas exchange measurements. The effect of branch excision on leaf gas exchange rates should be minimized and quantified to evaluate possible bias. We compared light-saturated leaf net photosynthetic rates measured on excised and intact branches. We selected branches positioned at three canopy positions, estimated relative to the top of the canopy: upper sunlit foliage, middle canopy foliage, and lower canopy foliage. We studied the variation of the effects of branch excision and transport among branches at these different heights in the canopy. After excision and transport, light-saturated leaf net photosynthetic rates were close to zero for most leaves due to stomatal closure. However, when the branch had acclimated to its new environmental conditions—which took on average 20 min—light-saturated leaf net photosynthetic rates did not significantly differ between the excised and intact branches. We therefore conclude that branch excision does not affect the measurement of light-saturated leaf net photosynthesis, provided that the branch is recut under water and is allowed sufficient time to acclimate to its new environmental conditions. © 2020 The Association for Tropical Biology and Conservation |
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UMR 5174 Laboratoire Evolution et Diversité Biologique, Université Paul Sabatier, CNRS, Toulouse, France |
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Blackwell Publishing Ltd |
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00063606 (Issn) |
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EcoFoG @ webmaster @ |
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960 |
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