Éditeur(s) : HAL CCSD Wiley
Résumé : Decomposing litter provides critical nutrients for plants, particularly in nutrient-poor ecosystems such as tropical forests. We hypothesised that decomposing litter improves the performance of a variety of tropical tree seedlings, and that this litter effect varies depending on the species of litter present in litter mixtures. We addressed these hypotheses with a large pot experiment manipulating a range of different litter mixtures of contrasting quality and using seedlings of four tree species from the Amazonian forest of French Guiana. In contrast to our initial hypothesis, decomposing litter had either neutral or negative impacts on seedling growth, despite strongly different growth rates, biomass allocation patterns and leaf and root traits among tree species. Tree species varied in their responses to litter additions, which were further modified by species identity of the added litter. Our data show litter species-specific effects on growth, biomass allocation and leaf and root traits of tropical tree seedlings. These results suggest that a net nutrient release from decomposing litter does not necessarily improve tree seedling growth, even under nutrient-limiting conditions. In conclusion, litter layer composition may affect seedling establishment and recruitment success beyond litter-derived plant nutrient availability, which may contribute to tree species composition and dynamics in the studied tropical forest.
ISSN: 1435-8603

hal-01032421
https://hal.archives-ouvertes.fr/hal-01032421
DOI : 10.1111/j.1438-8677.2011.00534.x

Éditeur(s) : HAL CCSD Wiley
Résumé : 1. Niche theory proposes that species differences underlie both coexistence within communities and the differentiation in species composition among communities via limiting similarity and environmental filtering. However, it has been difficult to extend niche theory to species-rich communities because of the empirical challenge of quantifying niches for many species. This has motivated the development of functional and phylogeny-based approaches in community ecology, which represent two different means of approximating niche attributes. 2. Here, we assess the utility of plant functional traits and phylogenetic relationships in predicting community assembly processes using the largest trait and phylogenetic data base to date for any set of species-rich communities. 3. We measured 17 functional traits for all 4672 individuals of 668 tree species co-occurring in nine tropical rain forest plots in French Guiana. Trait variation was summarized into two ordination axes that reflect species niche overlap. 4. We also generated a dated molecular phylogenetic tree based on DNA sequencing of two plastid loci (rbcL and matK) comprising 97% of the individuals and 91% of the species in the plots. 5. We found that, on average, co-occurring species had greater functional and, to a lesser extent, phylogenetic similarity than expected by chance. 6. We also found that functional traits and their ordination loadings showed significant, albeit weak, phylogenetic signal, suggesting that phylogenetic distance provides pertinent information on niche overlap in tropical tree communities. 7. Synthesis. We provide the most comprehensive examination to date of the relative importance of environmental filtering and limiting similarity in structuring tropical tree communities. Our results confirm that environmental filtering is the overriding influence on community assembly in these species-rich systems.
ISSN: 0141-6707

hal-01032423
https://hal.archives-ouvertes.fr/hal-01032423
DOI : 10.1111/j.1365-2745.2012.01966.x

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
1. Despite considerable interest in the application of plant functional traits to questions of community assembly and ecosystem structure and function, there is no consensus on the appropriateness of sampling designs to obtain plot-level estimates in diverse plant communities. 2. We measured 10 plant functional traits describing leaf and stem morphology and ecophysiology for all trees in nine 1-ha plots in terra firme lowland tropical rain forests of French Guiana (N = 4709). 3.We calculated, by simulation, the mean and variance in trait values for each plot and each trait expected under seven sampling methods and a range of sampling intensities. Simulated sampling methods included a variety of spatial designs, as well as the application of existing data base values to all individuals of a given species. 4. For each trait in each plot, we defined a performance index for each sampling design as the proportion of resampling events that resulted in observed means within 5% of the true plot mean, and observed variance within 20%of the true plot variance. 5. The relative performance of sampling designs was consistent for estimations of means and variances. Data base use had consistently poor performance for most traits across all plots, whereas sampling one individual per species per plot resulted in relatively high performance. We found few differences among different spatial sampling strategies; however, for a given strategy, increased intensity of sampling resulted in markedly improved accuracy in estimates of trait mean and variance. 6. We also calculated the financial cost of each sampling design based on data from our 'every individual per plot' strategy and estimated the sampling and botanical effort required. The relative performance of designs was strongly positively correlated with relative financial cost, suggesting that sampling investment returns are relatively constant. 7. Our results suggest that trait sampling for many objectives in species-rich plant communities may require the considerable effort of sampling at least one individual of each species in each plot, and that investment in complete sampling, though great, may be worthwhile for at least some traits.
ISSN: 0269-8463

hal-00594009
https://hal.archives-ouvertes.fr/hal-00594009

Éditeur(s) : HAL CCSD Wiley
Résumé : Tropical forests contain an important proportion of the carbon stored in terrestrial vegetation, but estimated aboveground biomass (AGB) in tropical forests varies two-fold, with little consensus on the relative importance of climate, soil and forest structure in explaining spatial patterns. Here, we present analyses from a plot network designed to examine differences among contrasting forest habitats (terra firme, seasonally flooded, and white-sand forests) that span the gradient of climate and soil conditions of the Amazon basin. We installed 0.5-ha plots in 74 sites representing the three lowland forest habitats in both Loreto, Peru and French Guiana, and we integrated data describing climate, soil physical and chemical characteristics and stand variables, including local measures of wood specific gravity (WSG). We use a hierarchical model to separate the contributions of stand variables from climate and soil variables in explaining spatial variation in AGB. AGB differed among both habitats and regions, varying from 78 Mg ha−1 in white-sand forest in Peru to 605 Mg ha−1 in terra firme clay forest of French Guiana. Stand variables including tree size and basal area, and to a lesser extent WSG, were strong predictors of spatial variation in AGB. In contrast, soil and climate variables explained little overall variation in AGB, though they did co-vary to a limited extent with stand parameters that explained AGB. Our results suggest that positive feedbacks in forest structure and turnover control AGB in Amazonian forests, with richer soils (Peruvian terra firme and all seasonally flooded habitats) supporting smaller trees with lower wood density and moderate soils (French Guianan terra firme) supporting many larger trees with high wood density. The weak direct relationships we observed between soil and climate variables and AGB suggest that the most appropriate approaches to landscape scale modeling of AGB in the Amazon would be based on remote sensing methods to map stand structure.
ISSN: 1354-1013

hal-01374829
https://hal.archives-ouvertes.fr/hal-01374829
DOI : 10.1111/j.1365-2486.2011.02432.x
PRODINRA : 183370

Éditeur(s) : HAL CCSD
Résumé :   Diplôme : DEA
il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION
Links between architectural stages of development (ASD), photosynthetic capacities and leaf characteristics in Tachigali melinonii (Caesalpiniaceae) were investigated in the tropical forest of French Guiana. Three ASD were sampled under three light conditions to elucidate the impact of ASD- and light-related changes on photosynthetic functional traits. Photosynthetic parameters (maximum rate in RubisCO carboxylation (Vcmax) and maximum rate of electron transport (Jmax) were estimated by adjusting a biochemical model (Farquhar et al., 1980) to response curves of CO2 assimilation rate to intercellular CO2 concentration, under saturated light. In addition, N and C foliar concentrations were analysed and N allocations to the carboxylation and bioenergetic processus of photosynthesis were calculated using the model of Niinemets and Tenhunen (1997). The variations in ecophysiological parameters observed were due to leaf anatomical and structural changes instead of changes in photosynthetic components, suggesting adjustments to light conditions. Tachigali melinonii thus appears to display morphological and anatomical plasticity at different ASDs and under different light conditions.
Une espèce forestière de Guyane Française, Tachigali melinonii (Caesalipiniaceae), a été choisie afin de regarder la variation des traits fonctionnels relatifs à la photosynthèse en fonction de la disponibilité en lumière et en fonction de son stade de développement architectural. Du fait du tempérament de l'espèce vis-à-vis de la lumière de type «struggling gambler» (ombrage nécessaire aux jeunes stades puis développement en pleine lumière), trois stades clefs de développement parmi la séquence de différenciation de l'espèce ainsi que trois environnements lumineux ont été choisis. Les capacités photosynthétiques foliaires ont été estimées à partir de l'ajustement de paramètres du modèle biochimique de photosynthèse foliaire (Farquhar et al. 1980) sur des courbes de réponses de l'assimilation de CO² (A) à des concentrations intracellulaires en CO² (Ci) croissantes, en condition de lumière saturante. La vitesse maximale de carboxylation Vcmax et le flux maximal d'électrons photosynthétiques Jmax ont ainsi été estimés et ensuite reliés aux caractéristiques structurales foliaires, notamment la concentration en azote, en carbone ainsi qu'avec la densité et l’épaisseur. Les fractions d'azote allouées aux processus photosynthétiques de carboxylation et de bioénergétique ont été calculées. Des variations, dues à un effet du stade de développement sur les paramètres étudiés ainsi qu’à un effet de la quantité de lumière disponible, ont été constatées. Ces variations sont surtout liées à des ajustements anatomiques et structuraux foliaires et non à des modifications de l’appareil photosynthétique. Tachigali melinonii semble donc modifier ses caractéristiques structurales foliaires en fonction de son stade de développement, ce qui suppose un contrôle ontogénique partiel, et en fonction de la disponibilité en lumière.
https://hal.archives-ouvertes.fr/hal-01189520

hal-01189520
https://hal.archives-ouvertes.fr/hal-01189520
PRODINRA : 44951

Éditeur(s) : HAL CCSD Elsevier
Résumé :  
Previous studies in lowland tropical rainforests of French Guiana showed that, among non-N2-fixing trees, two groups of late successional species contrasting in their leaf 15N natural abundance coexist, suggesting two different main ways of nitrogen acquisition. Two abundant late-successional species typically co-occurring in rainforests in French Guiana, namely Eperua falcata and Dicorynia guianensis, were chosen as representative of each group. Stable isotope techniques and measurements of potentials of microbial N transformation were performed to assess to what extent leaf 15N natural abundance of these species could be related to (i) d15N signatures of soil mineral N sources and (ii) the capacity of soil to express nitrification and denitrification (both processes being directly involved in the balance between NH4 + and NO3 - ). Soil d15N-NH4 + was roughly similar to leaf d15N of D. guianensis (around 3.5%), suggesting a preferential use of NH4 +, whereas in E. falcata, leaf d15N values were closer to root d15N-NO3 _ values (0.2 and _2.0%, respectively), suggesting a preferential use of NO3 _. These differences in N source utilization were not accompanied by differences in availability in soil NO3 _ or in intensity of microbial functions responsible for soil N mineral evolution. However, (i) under both tree species, these functions showed clear spatial partitioning, with denitrification occurring potentially in soil and nitrification in the litter layer, and (ii) E. falcata fine roots colonized the litter layer much more strongly than D. guianensis fine roots. This strongly suggests that (i) the contrasted leaf d15N values found in the two late-successional species reveal distinct N acquisition strategies and (ii) the ability of roots to predominantly exploit the litter layer (E. falcata) or the soil (D. guianensis) may constitute an important explanation of the observed differences. A complementarity between tree species, based on mineral N resource partitioning (itself resulting from a spatially structured location of the microbial functions responsible for the balance between NH4 + and NO3 - ), can thus be supposed.
ISSN: 0038-0717

hal-01032035
https://hal.archives-ouvertes.fr/hal-01032035
DOI : 10.1016/j.soilbio.2007.09.011

Éditeur(s) : HAL CCSD
Résumé : International audience
The tropical rainforest of Amazonia is one of the most species-rich ecosystems on earth, with an estimated 16000 tree species. Due to this high diversity, botanical identification of trees in the Amazon is difficult, even to genus, often requiring the assistance of parataxonomists or taxonomic specialists. Advances in informatics tools offer a promising opportunity to develop user-friendly electronic keys to improve Amazonian tree identification.Here, we introduce an original multi-access electronic key for the identification of 389 tree genera occurring in French Guiana terra-firme forests, based on a set of 79 morphological characters related to vegetative, floral and fruit characters. Its purpose is to help Amazonian tree identification and to support the dissemination of botanical knowledge to non-specialists, including forest workers, students and researchers from other scientific disciplines.The electronic key is accessible with the free access software Xper², and the database is publicly available on figshare: https://figshare.com/s/75d890b7d707e0ffc9bf (doi: 10.6084/m9.figshare.2682550).
ISSN: 1314-2011

hal-01369143
https://hal-sde.archives-ouvertes.fr/hal-01369143
DOI : 10.3897/phytokeys.68.8707

Éditeur(s) : HAL CCSD
Résumé : The main objective of this thesis was to study the influence of Guianan terra firme rainforests types on medium- and large-sized vertebrates community organization. First, we choose a model species which permitted to develop an appropriate abundance estimation method which take into account the imperfect detection and temporary immigration of mobile species, and to test environmental conditions effects at different spatial scales of analysis. Second, given that bias due to animal detection can be important in the abundance estimation, we determinated the relative role of environmental conditions and species biological traits on detection probability. From this methodological framework, we studied then processes of community organization, by identifying the main determinants involved in community organization, using composition and alpha and beta diversities, and, in a complementary manner, three metrics (taxonomic, functional, and phylogenetic). We sought from these general framework to determinate the relative role of environmental conditions and historical contingency, responsible for the current community organization, and to test the forest refugia hypothesis. Finally, we downscaled the analysis to determinate, and tried to disentangle the effects of environmental conditions and interspecific interactions on species co-occurrence. We used then functional traits to test the relationship between species co-occurrence and similarities.This thesis highlights the important role of historical contingency and facilitation in the structure of regional diversity and the local assembly processes of medium- and large-sized vertebrates, respectively, in French Guiana.
Cette thèse a pour but d’étudier l'influence de l'hétérogénéité des forêts de terre ferme en Guyane sur l'organisation des communautés de moyens et grands vertébrés. Nous avons, d'abord, choisi une espèce modèle afin de déterminer une méthode adéquate d'estimation d'abondance prenant en compte la détection imparfaite et l'immigration temporaire des espèces, et de tester l'effet des conditions environnementales à différentes échelles d'analyse. Puis, partant du constat que les biais dus à la détection dans l'estimation d'abondance pouvaient être importants, nous avons déterminé l'importance relative des conditions environnementales et des traits biologiques des espèces sur la probabilité de détection. A partir de ce cadre d'étude, nous avons étudié la composition et les diversités alpha et beta en utilisant de façon complémentaire les métriques taxonomique, fonctionnelle, et phylogénétique pour déterminer le rôle relatif de l'environnement et de la contingence historique dans l'organisation des communautés, et de tester l’hypothèse des refuges forestiers. Enfin, en descendant dans l'échelle d'analyse, nous avons tenté de démêler l'effet de l'environnement et des interactions interspécifiques sur la cooccurrence des espèces, et utilisé les traits fonctionnels des espèces pour tester le lien entre cooccurrence et similitude fonctionnelle. Cette thèse met en avant les rôles prépondérants de la contingence historique et de la facilitation dans, respectivement, la structuration de la diversité régionale et les processus d’assemblages locaux des communautés de moyens et grands vertébrés en Guyane.
https://tel.archives-ouvertes.fr/tel-01537779

NNT : 2017YANE0004
tel-01537779
https://tel.archives-ouvertes.fr/tel-01537779
https://tel.archives-ouvertes.fr/tel-01537779/document
https://tel.archives-ouvertes.fr/tel-01537779/file/these_thomas_denis.pdf

Éditeur(s) : HAL CCSD
Résumé : International audience
Studying the ecology of Leishmania parasites is essential for understanding and controlling the epidemiology of the diseases they cause. Despite their abundance and diversity in neotropical forests, few studies have been conducted to investigate the potential involvement of Chiroptera in the Leishmania pathogenic complexes. However, phlebotomine sand flies are known to colonize the same anthropized habitat, are attracted to bats, and are able to transmit trypanosomatids. Thus, 216 bats representing 29 species were sampled in the field in different primary and secondary forests of French Guiana where human cutaneous leishmaniases have been reported, together with 62 non-volant mammals. A series of 411 tissue samples representing 47 mammalian species were cultured and screened for the presence of Leishmania spp. by a genus-specific polymerase chain reaction. All 278 individuals surveyed were negative. Thus, bats do not appear to be involved in the Lishmania parasitic cycles in the Guyanas.
The American journal of tropical medicine and hygiene

halsde-00339305
https://hal.archives-ouvertes.fr/halsde-00339305

Éditeur(s) : EDP Sciences
Résumé : The present work was carried out on the hydroelectric reservoir Petit-Saut on the Sinnamary river in French Guiana. Measurements were performed during the wet and dry seasons along a longitudinal gradient, from upstream of the reservoir in two inflow rivers, to the Sinnamary estuary downstream of the dam. Gold extraction has led to a marked increase in suspended matter and total mercury (HgT) in one of the rivers. Dissolved monomethylmercury (MMHg) measured in surface waters were similar for both rivers: 0.03-0.05 ng l(-1) (1.0-1.7% of the dissolved HgT). These results indicate similar methylation efficiency and/or transfer of MMHg into the dissolved fraction of the water column, independently of the amounts of inorganic mercury transported. Dissolved MMHg concentrations in surface waters of the reservoir were similar to those in the rivers, but were more than 10 times higher in deep anoxic waters, up to 0.6 ng l(-1) (20 % of dissolved HgT). The MMHg concentration profiles in the water column suggest that methylation occurs mainly in anoxic waters and sediments in relation with the activity of sulfate reducing bacteria. Dissolved MMHg concentrations measured in the Sinnamary at the base of the dam were still high (0.5 - 0.6 ng l(-1); 20 to 35% of the dissolved HgT).
Journal de Physique IV (1155-4339) (EDP Sciences), 2003-05 , Vol. 107 , P. 327-331

Droits : EDP Sciences
http://archimer.ifremer.fr/doc/2003/publication-5283.pdf
DOI:10.1051/jp4:20030308
http://archimer.ifremer.fr/doc/00000/5283/

Éditeur(s) : Actes de colloques. Ifremer. Brest [ACTES COLLOQ. IFREMER.]. 1985
Résumé : Sexual differentiation of the marine leatherback turtle is sensitive to temperature. Incubation of eggs below 29 degree C results in 100% males, whereas incubationa bove 30 degree C results in 100% potential females at hatching. Therefore, the threshold temperature lies between 29 and 30 degree C as has been found for other marine turtles (Caretta caretta, Chelonia mydas ). Among hatchlings from natural nests in French Guiana, 10% were males, 20% were potential females and 70% had an intermediate phenotype. The sand temperature at 60 cm of depth, near one nest, was recorded and was found to vary between 29 and 30 degree C during the presumed thermosensitive period. These results will be useful to marine turtle hatcheries which seek to manipulate sex ratios among their neonates.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1983/acte-1241.pdf
http://archimer.ifremer.fr/doc/00000/1241/

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Whereas broad-scale Amazonian forest types have been shown to influence the structure of the communities of medium-to large-bodied vertebrates, their natural heterogeneity at smaller scale or within the terra firme forests remains poorly described and understood. Diversity indices of such communities and the relative abundance of the 21 most commonly observed species were compared from standardized line-transect data across 25 study sites distributed in undisturbed forests in French Guiana. We first assessed the relevance of a forest typology based on geomorphological landscapes to explain the observed heterogeneity. As previously found for tree beta-diversity patterns, this new typology proved to be a non-negligible factor underlying the beta diversity of the communities of medium-to large bodied vertebrates in French Guianan terra firme forests. Although the species studied are almost ubiquitous across the region, they exhibited habitat preferences through significant variation in abundance and in their association index with the different landscape types. As terra firme forests represent more than 90% of the Amazon basin, characterizing their heterogeneity-including faunal communities-is a major challenge in neotropical forest ecology.
ISSN: 0266-4674

hal-01502647
https://hal-agroparistech.archives-ouvertes.fr/hal-01502647
DOI : 10.1017/S0266467415000255

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
UNLABELLED: ABSTRACT: BACKGROUND: Malaria is a major health issue in French Guiana. Amerindian communities remain the most affected. A previous study in Camopi highlighted the predominant role of environmental factors in the occurrence of malaria. However, all parameters involved in the transmission were not clearly identified. A new survey was conducted in order to clarify the risk factors for the presence of malaria cases in Camopi. METHODS: An open cohort of children under seven years of age was set up on the basis of biologically confirmed malaria cases for the period 2001-2009. Epidemiological and observational environmental data were collected using two structured questionnaires. Data were analysed with a multiple failures multivariate Cox model. The influence of climate and the river level on malaria incidence was evaluated by time-series analysis. Relationships between Anopheles darlingi human biting rates and malaria incidence rates were estimated using Spearman's rank correlation. RESULTS: The global annual incidence over the nine-year period was 238 per 1,000 for Plasmodium falciparum, 514 per 1,000 for Plasmodium visa and 21 per 1,000 for mixed infections. The multivariate survival analysis associated higher malaria incidence with living on the Camopi riverside vs. the Oyapock riverside, far from the centre of the Camopi hamlet, in a home with numerous occupants and going to sleep late. On the contrary, living in a house cleared of all vegetation within 50 m and at high distance of the forest were associated with a lower risk. Meteorological and hydrological characteristics appeared to be correlated with malaria incidence with different lags. Anopheles darlingi human biting rate was also positively correlated to incident malaria in children one month later. CONCLUSIONS: Malaria incidence in children remains high in young children despite the appearance of immunity in children around three years of age. The closeness environment but also the meteorological parameters play an important role in malaria transmission among children under seven years of age in Camopi.
ISSN: 1475-2875

inserm-00633771
http://www.hal.inserm.fr/inserm-00633771
http://www.hal.inserm.fr/inserm-00633771/document
http://www.hal.inserm.fr/inserm-00633771/file/1475-2875-10-246.pdf
DOI : 10.1186/1475-2875-10-246

Éditeur(s) : HAL CCSD
Résumé : Biogenic volatile organic compound (BVOCs) emissions play an important role in regional air quality and global atmospheric chemistry. In addition, these natural VOC emissions serve important biological functions including attracting and repelling pollinators and herbivores. Some biological organisms use ambient air as a communication medium and the oxidation of these compounds brings about the concentration gradients sensed by insects and other organisms. Isoprene is the predominant BVOC emitted by vegetation and tropical forests are the dominant global source. This compound is very reactive in the atmosphere and contributes to the reactions that control tropospheric oxidant concentrations and thus the concentrations and lifetimes of longer-lived species. This paper presents a study on the seasonal variations in isoprene and some other significant BVOCs such as µ-pinene, µ-pinene, limonene, e-µ ocimene and longifolene, measured at the Guyaflux Tower located in a wet tropical forest in Paracou French Guiana (5o16´54´´N, 52o54´44´´W), during the year of 2011, using the Relaxed Eddy Accumulation technique at approximately 20 meters high above the canopy. The results show a lower concentration of isoprene during the month of February and March which correspond to the wet season with an average of 0,545 µg/m3 and 0,341 µg/m3, respectively followed by a slight increase in middle April (still wet season) and a higher concentration later in mid-June. The same behavior was observed for µ-pinene with higher concentrations for the same periods as isoprene however with a smaller increase. All the other compounds had concentrations below 1 µg/m3during the whole year: The monoterpene, e-µ ocimene, was observed and is known as a stress compound but the vegetation at the site did not face any known severe stress condition such as excessive drought or flooding. Concerning the fluxes, the results showed that just a small amount of BVOCs were deposited by wet or dry process and the majority of them were released in the atmosphere. Isoprene was by far the biogenic volatile organic compound with the highest concentration and flux, followed by alpha-pinene. The lowest concentration and flux rate for all the studied compounds was observed during the months of March and late July and beginning of August indicating a lower production of those BVOCs by vegetation during those periods. Previous limited studies in Amazonia and the Congo suggested that a higher concentration and flux rate of isoprene and µ-pinene should be expected during the dry season with lower emissions during the wet season, which is in relative agreement with what was observed at this tropical forest site in French Guiana. The exceptions were observed in April and June which correspond to a long wet period in which the concentration of isoprene and µ-pinene increased more than it was expected for this time of the year. The observations will be compared to output from the global chemistry transport model CAM-chem, which includes the MEGAN biogenic emissions model.
10th EGU General Assembly
vienne, Austria

hal-01204214
https://hal.archives-ouvertes.fr/hal-01204214
PRODINRA : 276525

Éditeur(s) : HAL CCSD Ecological Society of America
Résumé : International audience
The expansion of selective logging in tropical forests may be an important source of global carbon emissions. However, the effects of logging practices on the carbon cycle have never been quantified over long periods of time. We followed the fate of more than 60 000 tropical trees over 23 years to assess changes in aboveground carbon stocks in 48 1.56-ha plots in French Guiana that represent a gradient of timber harvest intensities, with and without intensive timber stand improvement (TSI) treatments to stimulate timber tree growth. Conventional selective logging led to emissions equivalent to more than a third of aboveground carbon stocks in plots without TSI (85 Mg C/ha), while plots with TSI lost more than one-half of aboveground carbon stocks (142 Mg C/ha). Within 20 years of logging, plots without TSI sequestered aboveground carbon equivalent to more than 80% of aboveground carbon lost to logging (-70.7 Mg C/ha), and our simulations predicted an equilibrium aboveground carbon balance within 45 years of logging. In contrast, plots with intensive TSI are predicted to require more than 100 years to sequester aboveground carbon lost to emissions. These results indicate that in some tropical forests aboveground carbon storage can be recovered within half a century after conventional logging at moderate harvest intensities.
ISSN: 1051-0761

hal-00598787
https://hal.archives-ouvertes.fr/hal-00598787

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Although ants may induce community-wide effects via changes in physical habitats in terrestrial environments, their influence on aquatic communities living in plant-held waters remains largely underexplored. The neotropical tank-bromeliad Aechmea mertensii (Bromeliaceae) occurs along forest edges in ant-gardens initiated by Camponotus femoratus or by Pachycondyla goeldii. Its leaves form wells that hold rainwater and provide suitable habitats for many aquatic organisms. We postulated that these ant-plant mutualisms indirectly affect the microbial community structure via changes in the environmental conditions experienced by the plants. To test this hypothesis, we analyzed the protist communities from 63 tank-bromeliads associated with either C. femoratus or P. goeldii (hereafter Cf-Aechmea and Pg-Aechmea) along a forest edge in French Guiana. For each plant, a large number of environmental variables (including habitat structure, food resources, incident radiation and the presence of aquatic invertebrates) were quantified to determine their relative importance in driving any observed differences across ant-associated plants. Pg-Aechmea are located in sun-exposed areas and hold low volumes of water and low amounts of detritus, whereas Cf-Aechmea are located in partially shaded areas and accumulate higher amounts of water and detritus. Protists (i.e., protozoa and algae) inhabiting Cf-Aechmea exhibit greater richness and abundances than those in Pg-Aechmea. Variations in detritus content, number of leaves, incident radiation, and the epiphyte richness of the ant-garden were the main factors explaining the variation in protist richness. A shift in the functional group composition of protists between bromeliads tended by different ant species suggested that mutualistic ants indirectly mediate changes in the microbial food web.
Basic and Applied Ecology

hal-00913126
https://hal.archives-ouvertes.fr/hal-00913126
https://hal.archives-ouvertes.fr/hal-00913126/document
DOI : 10.1016/j.baae.2012.10.002
OATAO : 10190

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This paper discusses and analyses the productivity of solar home systems in isolated areas in French Guiana, a region characterized by specific human and environmental conditions.Its aim is a better understanding of the attitudes, expectations, and relationship of the users towards the solar home system. The data collected made it possible to make suggestions for adapting the photovoltaic systems to their environment by taking into account social, cultural, and geoclimatic specificities. Analysis of on-site productivity provides valuable information on energy profiles and types of use. Field surveys made it possible to associate users’ perception of the energy production equipment and their degree of satisfaction with operating efficiency and on-site maintenance. This aspect is essential for analyzing the actual rate of use of the energy that is theoretically available.Parallel to these surveys, the results of the study carried out on the performance of the solar home systems made it possible to learn the quantitative aspects of the energy produced and consumed as well as the qualitative aspects of the parameters that condition the performance of the photovoltaic systems.After keyboarding, the subjective, qualitative as well as the quantitative variables were processed using a statistical analysis program in order to determine the correlations between them and to prepare the final conclusions.
ISSN: 1364-0321

hal-01304585
https://hal.archives-ouvertes.fr/hal-01304585
https://hal.archives-ouvertes.fr/hal-01304585/document
https://hal.archives-ouvertes.fr/hal-01304585/file/article%20RSER%20Hal.pdf
DOI : 10.1016/j.rser.2009.06.015

Éditeur(s) : Cambridge Univ Press
Résumé : This paper offers a theoritical and empirical model of ecosystem-based fishery management. A multi-species and multi-fleet integrating Lotka-Volterra trophic dynamics as well as production and profit assessments is developed and applied to the coastal fishery of French Guiana. This small-scale fishery constitutes a challenging example with high fish biodiversity, several non-selective fleets and a potentially increasing local food demand due to demographic growth. The dynamic model is calibrated with 13 species and four fleets using monthly catch and effort data from 2006 to 2009. Several contrasted fishing scenarios including status quo, total closure, economic and viable strategies are then simulated. They are compared from the viewpoints of both biodiversity preservation and socioeconomic performance, assuming fixed landing prices and fixed costs. We show that fishing outputs, including food supply and fleet profitability, can be sustained on average but a loss of species cannot be avoided.
Environment And Development Economics (1355-770X) (Cambridge Univ Press), 2013-06 , Vol. 18 , P. 245-269

Droits : Cambridge University Press 2013
http://archimer.ifremer.fr/doc/00124/23483/21311.pdf
http://archimer.ifremer.fr/doc/00124/23483/21375.pdf
DOI:10.1017/S1355770X13000065
http://archimer.ifremer.fr/doc/00124/23483/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Toxoplasma gondii is highly virulent in New World monkeys, but despite numerous outbreaks observed in captive populations there are few reports of molecular characterization of strains. In this article, we describe two outbreaks of toxoplasmosis that occurred in 2001 and 2006 in an outdoor captive breeding colony of squirrel monkeys (Saimiri sciureus) kept by the Institut Pasteur in French Guiana. A microsatellite DNA analysis of the biological samples collected in the 2001 and 2006 outbreaks showed that two different Toxoplasma strains were involved. The 2001 strain exhibited a type II genotype whereas the 2006 strain showed a combination of type I, type III and atypical alleles. Infection could be related to oocysts contaminating water or food, or to ingestion of rats by monkeys. In 2006, a second episode was observed 3 weeks after the first, and was believed to be related to direct contamination by tachyzoites of bronchopulmonary origin from dying monkeys of the first event. During both outbreaks, a total of 50 monkeys died and none recovered spontaneously, confirming the virulence of both type II and non-type II Toxoplasma strains in New World monkeys.
ISSN: 0304-4017

hal-00408048
https://hal.archives-ouvertes.fr/hal-00408048
DOI : 10.1016/j.vetpar.2009.04.004
PUBMED : 19423226

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
BACKGROUND: Reliable molecular typing tools are required for a better understanding of the molecular epidemiology of Plasmodium vivax. The genes msp3a and msp1_block5 are highly polymorphic and have been used as markers in many P. vivax population studies. These markers were used to assess the genetic diversity of P. vivax strains from French Guiana (South America) and to develop a molecular typing protocol. METHODS: A total of 120 blood samples from 109 patients (including 10 patients suffered from more than one malaria episode, samples were collected during each episode) with P. vivax infection were genotyped. All samples were analysed by msp3a PCR-RFLP and msp1_b5 gene sequencing was performed on 57 samples. Genotyping protocol applied to distinguish between new infection or relapse from heterologus hypnozoites and treatment failure or relapse from homologus hypnozoites was based on analysing first msp3a by PCR-RFLP and secondly, only if the genotypes of the two samples are identical, on sequencing the msp1_b5 gene. RESULTS: msp3a alleles of three sizes were amplified by PCR: types A, B and C. Eleven different genotypes were identified among the 109 samples analysed by msp3a PCR-RFLP. In 13.8% of cases, a mixed genotype infection was observed. The sequence of msp1_b5 gene revealed 22 unique genotypes and 12.3% of cases with mixed infection. In the 57 samples analysed by both methods, 45 genotypes were found and 21% were mixed. Among ten patients with two or three malaria episodes, the protocol allowed to identify five new infections or relapses from heterologous hypnozoites and six treatment failures of relapses from homologous hypnozoites. CONCLUSION: The study showed a high diversity of msp3a and msp1_b5 genetic markers among P. vivax strains in French Guiana with a low polyclonal infection rate. These results indicated that the P. vivax genotyping protocol presented has a good discrimination power and can be used in clinical drug trials or epidemiological studies.
ISSN: 1475-2875

pasteur-00590981
https://hal-riip.archives-ouvertes.fr/pasteur-00590981
DOI : 10.1186/1475-2875-8-40
PUBMED : 19284592