Éditeur(s) : AGU
Résumé : Submarine canyons are narrow but deep submarine valleys that extend for hundreds of meters. They represent the most impressive structures that shape the present morphology of passive continental margins. They can occur off the mouth of rivers: the Tagus, Zaire, Amazon, and Orinoco in the Atlantic; the Indus in the Indian Ocean; and the Var, Rhone, and Ebro in the Mediterranean. Some are at times disconnected from any stream mouth such as the Nazare canyon, off Portugal, despite the fact that it is close to the coast. Some were connected to a river mouth during lowstands of sea level, such as the Wilmington canyon in the northwest Atlantic, or the Blackmud canyon in the northeast Atlantic.
EOS, Transactions American Geophysical Union (0096-3941) (AGU), 2004-07-06 , Vol. 85 , N. 27 , P. 257

Droits : 2004 AGU
http://archimer.ifremer.fr/doc/00071/18201/15769.pdf
DOI:10.1029/2004EO270001
http://archimer.ifremer.fr/doc/00071/18201/

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) : Apud Frid. Fleischer in comm
Extrait de : Flora brasiliensis. Volumen I. Pars I (après l'index de la deuxième partie)
Résumé : Ile de sable sur le fleuve Amazone, province de Paraensis
Tab. physiognom XI.
Siècle(s) traité(s) : 19
Permalien : http://www.manioc.org/images/TLS17055-0251i1
TLS17055-0251i1

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : The patterns of the distribution of fungal species and their potential interactions with trees remain understudied in Neotropical rainforests, which harbor more than 16,000 tree species, mostly dominated by endomycorrhizal trees. Our hypothesis was that tree species shape the non-mycorrhizal fungal assemblages in soil and litter and that the diversity of fungal communities in these two compartments is partly dependent on the coverage of trees in the Neotropical rainforest. In French Guiana, a long-term plantation and a natural forest were selected to test this hypothesis. Fungal ITS1 regions were sequenced from soil and litter samples from within the vicinity of tree species. A broad range of fungal taxa was found, with 42 orders and 14 classes.Significant spatial heterogeneity in the fungal communities was found without strong variation in the species richness and evenness among the tree plots. However, tree species shaped the fungal assemblages in the soil and litter, explaining up to 18 % of the variation among the communities in the natural forest.These results demonstrate that vegetation cover has an important effect on the structure of fungal assemblages inhabiting the soil and litter in Amazonian forests, illustrating the relative impact of deterministic processes on fungal community structures in these highly diverse ecosystems.
ISSN: 0095-3628

hal-01595373
https://hal.archives-ouvertes.fr/hal-01595373
DOI : 10.1007/s00248-016-0839-0
PRODINRA : 395655
PUBMED : 27645139

Extrait de : La Jangada, huit cents lieues sur l'Amazone. De Rotterdam à Copenhague, à bord du yacht à vapeur (p.320)
Siècle(s) traité(s) : 20
Droits : Domaine public
Permalien : http://www.manioc.org/images/FRA120680083i1
FRA120680083i1

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Sites of monomethylmercury (MMHg) production in Amazonian regions have been identified in hydraulic reservoirs, lake sediments and wetlands, but tailings ponds have not yet received sufficient attention for this purpose. This work evidenced high MMHg production within the water column and the interstitial water of two tailings ponds of French Guiana Au mines located; (i) in a small scale exploitation (Combat) where Hg was used for Au amalgamation, and (ii) in an industrial on-going Au mine (Yaoni) processing without Hg. The (MMHg)(D) maximum (2.5 ng L-1) occurred in the oxic water column above the sediment-water interface (SWI) of the most recent tailings pond (Combat), where the substrate was fresh, the redox transition was sharp and the pool of total Hg was large. In the Yaoni pond, the (MMHg)(D) maximum concentration (1.4 ng L-1) was located at the SWI where suboxic conditions prevailed. Using the (MMHg)(D) concentration as a proxy for Hg methylation rates, the present results show that Hg methylation may occur in various redox conditions in tailings ponds, and are favored in areas where the organic matter regeneration is more active. A 3-month long laboratory experiment was performed in oxic and anoxic boxes filled with high turbidity waters from the Combat Au mine to simulate tailings ponds. Slaked lime was added in an experimental set (2 mg L-1)and appeared to be very efficient for the reduction of suspended particulate matter (SPM) to environmentally acceptable concentrations. However, at the end of the experiment, large (MMHg)(D) concentrations were monitored under treated anoxic conditions with the (MMHg)(D) maximum located at the SWI above the Fe-reducing zones. No (MMHg)(D) was detected in oxic experiments. The use of slaked lime for SPM decantation appears to be an efficient and non-onerous process for Au miners to avoid Hg methylation in tailings ponds when it is combined with rapid drainage of the mine waters. A subsequent human intervention is however necessary for the recovery of soil structure through the cover of dried ponds with organic rich materials and reforestation to avoid the stagnation of rain waters and the occurrence of anoxia. (C) 2010 Elsevier Ltd. All rights reserved.
Applied Geochemistry (0883-2927) (Pergamon-elsevier Science Ltd), 2011-02 , Vol. 26 , N. 2 , P. 222-229

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00030/14117/12133.pdf
DOI:10.1016/j.apgeochem.2010.11.022
http://archimer.ifremer.fr/doc/00030/14117/

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The exchanges of carbon, water and energy between the atmosphere and the Amazon basin have global implications for the current and future climate. Here, the global atmospheric inversion system of the Monitoring of Atmospheric Composition and Climate (MACC) service is used to study the seasonal and interannual variations of biogenic CO 2 fluxes in Amazonia during the period 2002–2010. The system assimilated surface measurements of atmospheric CO 2 mole fractions made at more than 100 sites over the globe into an atmospheric transport model. The present study adds measurements from four surface stations located in tropical South America, a region poorly covered by CO 2 observations. The estimates of net ecosystem exchange (NEE) optimized by the inversion are compared to an independent estimate of NEE upscaled from eddy-covariance flux measurements in Amazonia. They are also qualitatively evaluated against reports on the seasonal and interannual variations of the land sink in South America from the scientific literature. We attempt at assessing the impact on NEE of the strong droughts in 2005 and 2010 (due to severe and longer-than-usual dry seasons) and the extreme rainfall conditions registered in 2009. The spatial variations of the seasonal and in-terannual variability of optimized NEE are also investigated. While the inversion supports the assumption of strong spatial heterogeneity of these variations, the results reveal critical limitations of the coarse-resolution transport model, the surface observation network in South America during the recent years and the present knowledge of modelling uncertainties in South America that prevent our inversion from capturing the seasonal patterns of fluxes across Amazonia. However, some patterns from the inversion seem consistent with the anomaly of moisture conditions in 2009.
ISSN: 1680-7316

hal-01557375
https://hal.univ-lorraine.fr/hal-01557375
https://hal.univ-lorraine.fr/hal-01557375/document
https://hal.univ-lorraine.fr/hal-01557375/file/acp-15-8423-2015.pdf
DOI : 10.5194/acp-15-8423-2015-supplement

Éditeur(s) : HAL CCSD
Résumé : CIRAD, Montpellier, Perspective
In the Brazilian Amazon, degraded forests dominate the landscapes on the agricultural frontiers. This region is now facing a major challenge: halting degradation and sustainably managing these forests. Today, degraded forests represent a class of forest in their own right. They can nevertheless play a key role in combating climate change, and can also help to improve the ecological functioning of the different territories. Implementing public policies with the twin objectives of reducing degradation and promoting these forests implies strong support from research. In this Perspective, we focus on four research priorities: developing methods to characterise and monitor degraded forests; drafting specific forest management plans; understanding the role played by all social actors; and supporting policies at the territorial level.
En Amazonie brésilienne, les forêts dégradées dominent les paysages des fronts pionniers. Un grand défi attend désormais cette région : stopper la dégradation et gérer durablement ces forêts. Les forêts dégradées représentent aujourd’hui une catégorie de forêt à part entière. Elles peuvent néanmoins jouer un rôle majeur pour lutter contre le changement climatique. Elles peuvent aussi contribuer à un meilleur fonctionnement écologique des territoires. Développer des politiques publiques visant le double objectif de réduire la dégradation et de valoriser ces forêts implique un appui fort de la recherche. Dans ce Perspective, nous mettons l’accent sur quatre priorités de recherche : développer des méthodes de caractérisation et de suivi des forêts dégradées, élaborer des plans d’aménagement spécifiques, comprendre le rôle joué par tous les acteurs sociaux et accompagner les politiques à l’échelle territoriale.
Na Amazônia brasileira, as florestas degradadas dominam as paisagens das frentes pioneiras. Atualmente, esta região enfrenta um grande desafio: parar a degradação e fazer a gestão sustentável dessas florestas. As florestas degradadas são atualmente parte integrante de uma categoria de florestas. No entanto, elas podem desempenhar um papel importante na luta contra as mudanças climáticas e podem contribuir para um melhor funcionamento ecológico dos territórios. Desenvolver políticas públicas com o duplo objetivo de reduzir a degradação e melhorar a condição dessas florestas implica um forte apoio da pesquisa. Neste Perspective, nós focalizamos em quatro prioridades de pesquisa: desenvolver os métodos de caracterização e monitoramento das florestas degradadas, elaborar planos específicos de ordenamento do território, compreender o papel desempenhado por todos os atores sociais e acompanhar as politicas em escala territorial.
https://hal.archives-ouvertes.fr/hal-01537653

Droits : http://creativecommons.org/licenses/by-nc-sa/
hal-01537653
https://hal.archives-ouvertes.fr/hal-01537653
https://hal.archives-ouvertes.fr/hal-01537653/document
https://hal.archives-ouvertes.fr/hal-01537653/file/Persp40_LBLanc%20FR.pdf
https://hal.archives-ouvertes.fr/hal-01537653/file/Persp40_LBLanc%20PORT.pdf

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Avec 130 espèces identifiées, l’Amazonie est la région du monde qui abrite le plus grand nombre d’espèces d’abeilles sans dard. Cette diversité reste assez peu exploitée par les communautés locales, même si certaines pratiques, comme la recherche de nids ou l’extraction de miel sauvage, sont sans doute très anciennes. La diversification des usages du miel et l’utilisation récente du pollen à des fins médicinales, pourraient les modifier durablement, et les essaims devenir l’objet de toutes les attentions.Dans la Réserve d’Amanã, les dix-huit agriculteurs, que nous avons interrogés et parfois filmés lors de mises en situation, ont conscience de cette évolution et la plupart s’en réjouissent. En tant qu’éleveurs d’abeilles, ils savent aujourd’hui que pour récolter du miel, ils ne sont plus contraints de chercher des colonies sauvages, de les déloger pour finalement les détruire. Mais on aurait tort de croire que ces pratiques anciennes constituent, dans le cas étudié, une menace pour l’entomofaune ; d’une part parce que la pression sur les nids reste très limitée, d’autre part parce que les extractions ne concernent qu’un nombre réduit d’espèces. C’est pourquoi il est indispensable de mieux décrire ces techniques et de les valoriser comme des savoir-faire ancestraux.
With 130 identified species, the Amazon is one region of the world which shelters the largest number of species of bees without a sting. This diversity is rarely exploited by the local communities even if certain practices like the search of honeycombs or the extraction of wild honey are very ancient. The diversification of the uses of honey and the recent use of the pollen for medicinal purposes could modify these sustainable practices and the bee swarms could become a major center of attention.In the Amanã Reserve, the eighteen farmers that were questioned and sometimes filmed while they were in work situations, are conscious of this revolution and most of them rare pleased with this new trend. As working beekeepers, they know that to collect some honey, they are no longer compelled to look for wild colonies, to dislodge them from their natural habitat, which would finally destroy them. Correspondingly it would be wrong to believe that these ancient practices, extraction of wild honey, represent in the studied case, a threat for the entomofauna. On one hand, the importance on honeycombs remains very limited, also on the other hand, the extractions concern just a few number of bee species. That is why it is essential to better specify these techniques and to value them as an ancestral knowledge.
Brésil

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.10279
http://journals.openedition.org/etudescaribeennes/10279

Éditeur(s) : HAL CCSD Wiley
Résumé : [b]Aim[/b][br/] Many tropical tree species have poorly delimited taxonomic boundaries and contain undescribed or cryptic species. We examined the genetic structure of a species complex in the tree genus Carapa in the Neotropics in order to evaluate age, geographic patterns of diversity and evolutionary relationships, and to quantify levels of introgression among currently recognized species.[br/] [br/] [b]Location[/b][br/] Lowland moist forests in the Guiana Shield, the Central and Western Amazon Basin, Chocó and Central America.[br/] [br/] [b]Methods[/b][br/] Genetic structure was analysed using seven nuclear simple sequence repeats (nuSSR), five chloroplast SSRs (cpSSR), and two chloroplast DNA (cpDNA) intergenic sequences (trnH-psbA and trnC-ycf6). Bayesian clustering analysis of the SSR data was used to infer population genetic structure and to assign 324 samples to their most likely genetic cluster. Bayesian coalescence analyses were performed on the two cpDNA markers to estimate evolutionary relationships and divergence times.[br/] [br/] [b]Results[/b][br/] Two genetic clusters (nu_guianensis and nu_surinamensis) were detected, which correspond to the Neotropical species C. guianensis (sensu latu) and C. surinamensis. Fourteen cpDNA haplotypes clustered into six haplogroups distributed between the two nuclear genetic clusters. Divergence between the haplogroups was initiated in the Miocene, with some haplotype structure evolving as recently as the Pleistocene. The absence of complete lineage sorting between the nuclear and chloroplast genomes and the presence of hybrid individuals suggest that interspecific reproductive barriers are incomplete. NuSSR diversity was highest in C. guianensis and, within C. guianensis, cpDNA diversity was highest in the Central and Western Amazon Basin. Regional genetic differentiation was strong but did not conform to an isolation-by-distance process or exhibit a phylogeographical signal.[br/] [br/] [b]Main conclusions[/b][br/] The biogeographical history of Neotropical Carapa appears to have been influenced by events that took place during the Neogene. Our results point to an Amazonian centre of origin and diversification of Neotropical Carapa, with subsequent migration to the Pacific coast of South America and Central America. Gene flow apparently occurs among species, and introgression events are supported by inconsistencies between chloroplast and nuclear lineage sorting. The absence of phylogeographical structure may be a result of the ineffectiveness of geographical barriers among populations and of reproductive isolation mechanisms among incipient and cryptic species in this species complex.
ISSN: 0305-0270

hal-01032395
https://hal.archives-ouvertes.fr/hal-01032395
DOI : 10.1111/j.1365-2699.2011.02678.x

Éditeur(s) : Elsevier
Résumé : During the Fanindien 2006 cruise of R/V 'Beautemps-Beaupre', high resolution multibeam bathymetry, sub-bottom profiling and sediment coring was carried out along the East African margin, offshore Tanzania and Mozambique (Indian Ocean). The newly acquired data reveal the presence of a giant deep-sea valley (the Tanzania channel) that is more than 10 km wide at 4000 m water depth, along the continental rise. The valley remains similar to 70 m deep and 7 km wide at 800 km from the Tanzania coast. Morphological comparison with worldwide submarine channels show that the Tanzania channel is one of the largest known submarine valleys. This discovery brings new light on development of submarine valleys that drain sediments originated from the East African Rift System (EARS) highlands (i.e. the Tanzania channel and its neighbor Zambezi channel located similar to 1000 km southward). Both of the systems have a morphology markedly different to the classical sinuous, V-shaped channels located at similar latitudes (e.g. the Zaire or Amazon channels). Their submarine drainage system consists of a downslope converging tributary canyons joining a central trunk channel in the continental rise. The presence of such giant deep-sea drainage systems is probably linked to a strong structural control on the sediment pathway, associated to a massive sediment transfer towards the Indian Ocean in relation with the tectonic activity of the East African Rift System (i.e. the uplift periods trough mid-Miocene and Plio-Pleistocene times) and its interplay with the East African equatorial climate changes.
Marine Geology (0025-3227) (Elsevier), 2008-12 , Vol. 255 , N. 3-4 , P. 179-185

Droits : 2008 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00324/43491/42958.pdf
DOI:10.1016/j.margeo.2008.09.002
http://archimer.ifremer.fr/doc/00324/43491/

Éditeur(s) : HAL CCSD
Résumé : il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : ACTIVITY_REPORT
Understanding genomic evolution in wild populations is of particular importance because evolution is a central process in our understanding of populations’ history and their future response to global changes. In addition to fundamental knowledge, the study of populations’ evolution has wide applications such as conservation/restoration genetics or epidemiology. Indeed, genetic diversity is the ‘fuel’ for populations’ evolution and adaptation to new conditions, and estimating the extent and the geographic structure of genetic diversity, as well as identifying the evolutionary forces behind (demography, gene flow, and adaptation) are thus major challenges in the current context of global changes. [br/]A particular attention is currently devoted to the process of genetic divergence in wild populations, with emphases on gene flow, local adaptation, and their interactions. Indeed, adaptation in wild populations is supported in many species by many kinds of experiments based on both quantitative phenotypic traits and molecular data. However, the processes governing populations’ evolution are poorly understood in the tropical rainforest of Amazonia, and the relative influence of neutral and adaptive processes are continuously discussed. [br/]I am a young scientist interested in the process of genomic divergence in wild (tree) populations. I aimed at understanding how evolution structures the genetic diversity and governs molecular divergence in wild populations, with particular emphases on gene flow and local adaptation. During five years as a young scientist, I worked on answering the following questions, focusing on two tree species occupying vulnerable areas: mainly [i]Eperua falcata[/i] in Amazonia and, to a lesser extent, [i]Abies alba[/i] in the Mediterranean area.[br/][u]Scientific questions:[/u][br/]- Which evolutionary drivers are responsible of the structure of genetic diversity in wild populations occupying wide areas? This question was addressed at different geographical scales: from large (regional) to very local (microgeographic) scales. [br/]- What is the relative influence of neutral (gene flow, inbreeding) and adaptive drivers in the process of genetic divergence?[br/]- Is microgeographic adaptation possible in spite of extensive gene flow between populations occupying the extreme boundaries of an ecological gradient? [br/]- What is the extent of natural selection in the (whole) genome of wild populations? [br/][br/]My research work is at the interface between three promising disciplines: Evolutionary genomics (i.e. the study of populations evolution and the evolutionary drivers behind), Bioinformatics (i.e. the treatment of next-generation data), and Bayesian modelling (i.e. the empirical calibration of complex mechanistic model). I intend to take advantage of the recent advances in sequencing and informatic technologies to bring up to date the field of ecological genetics and evolutionary biology, by developing modern research strategies to study the process of genomic divergence in wild populations.
https://hal.archives-ouvertes.fr/hal-01204218

hal-01204218
https://hal.archives-ouvertes.fr/hal-01204218
PRODINRA : 286326

Éditeur(s) : HAL CCSD eLife Sciences Publication
Résumé : When 2 Mha of Amazonian forests are disturbed by selective logging each year, more than 90 Tg of carbon (C) is emitted to the atmosphere. Emissions are then counterbalanced by forest regrowth. With an original modelling approach, calibrated on a network of 133 permanent forest plots (175 ha total) across Amazonia, we link regional differences in climate, soil and initial biomass with survivors' and recruits' C fluxes to provide Amazon-wide predictions of post-logging C recovery. We show that net aboveground C recovery over 10 years is higher in the Guiana Shield and in the west (21 +/- 3 Mg C ha(-1)) than in the south (12 +/- 3 Mg C ha(-1)) where environmental stress is high (low rainfall, high seasonality). We highlight the key role of survivors in the forest regrowth and elaborate a comprehensive map of post-disturbance C recovery potential in Amazonia.
ISSN: 2050-084X

hal-01606806
https://hal.archives-ouvertes.fr/hal-01606806
DOI : 10.7554/eLife.21394
PRODINRA : 389858

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study investigated the clinical epidemiology and resistance mechanisms of Acinetobacter baumannii and characterised the clonal diversity of carbapenem-resistant A. baumannii (CRAB) during an ICU-associated outbreak at Cayenne Hospital, French Guiana. All non-duplicate A. baumannii isolates from 2008 to 2014 were tested for antibiotic susceptibility by disk diffusion. Multilocus sequence typing, pulsed-field gel electrophoresis (PFGE) and characterisation of carbapenemase-encoding genes were performed on CRAB. Of the 441 A. baumannii isolates, most were from males (54.0%) and were detected mainly from the ICU (30.8%) and medicine wards (21.8%). In the ICU, strains were mainly isolated from the respiratory tract (44.1%) and bloodstream (14.0%), whereas in medicine wards they mainly were from wound/drainage (36.5%) and bloodstream (25.0%). A. baumannii showed the greatest susceptibility to piperacillin/tazobactam (92.7%), imipenem (92.5%), colistin (95.6%) and amikacin (97.2%), being lower in the ICU and medicine wards compared with other wards. An outbreak of OXA-23-producing CRAB occurred in the 13-bed ICU in 2010. CRAB strains were more co-resistant to other antimicrobials compared with non-CRAB. Molecular genetics analysis revealed five sequence types [ST78, ST107 and ST642 and two new STs (ST830 and ST831)]. Analysis of PFGE profiles indicated cross-transmissions of CRAB within the ICU, between the ICU and one medicine ward during transfer of patients, and within that medicine ward. This study provides the first clinical and molecular data of A. baumannii from French Guiana and the Amazon basin. The ICU was the highest risk unit of this nosocomial outbreak of OXA-23-producing CRAB, which could subsequently disseminate within the hospital.
ISSN: 0924-8579

hal-01506828
https://hal.archives-ouvertes.fr/hal-01506828
PUBMED : 27236843

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Coarse woody debris (CWD, dead wood sections a parts per thousand yen10 cm diameter) represents a large store of carbon in tropical forests; however, estimates of the flux of carbon from CWD in these forests remain poorly constrained. The objective of this study was to resolve the dry/wet season response of respiration in CWD (R (cwd)), and investigate the importance of biotic and abiotic factors for predicting the seasonal change of R (cwd) at the ecosystem level. This study presents a 4-month time series of R (cwd) measurements conducted on 42 dead trees (26 species) at the Paracou Research Station in French Guiana. R (cwd) measurements were repeated 13 times on each CWD sample from July to November 2011, spanning the transition from wet to dry season, and then from dry season to the following wet season. Seasonal drought caused monthly R (cwd) to drop by 20.5 +/- A 5.1% over the wet-dry transition. Changes in woody tissue moisture content explained 41.9% of the measured seasonal variability in R (cwd), but 60% of the seasonal variability in mean forest R (cwd) rates could be modelled using surface soil water content. We estimate that R (cwd) is approximately 5% of annual ecosystem respiration (R (eco)) and that seasonal variations in R (cwd) contribute appreciably to seasonal variations of R (eco), and should be included in functional models simulating the response of tropical rainforest ecosystems to current and future climate.
ISSN: 1432-9840

hal-01032431
https://hal.archives-ouvertes.fr/hal-01032431
DOI : 10.1007/s10021-013-9684-x

Éditeur(s) : HAL CCSD Ecological Society of America
Résumé : Tropical plant diversity is extraordinarily high at both local and regional scales. Many studies have demonstrated that natural enemies maintain local diversity via negative density dependence, but we know little about how natural enemies influence beta-diversity across habitats and/or regions. One way herbivores could influence plant beta-diversity is by driving allocation trade-offs that promote habitat specialization across resource gradients. We therefore predicted that increasing resource availability should be accompanied by increasing herbivory rates and decreasing plant allocation to defense. Second, relative abundances within plant lineages are predicted to reflect patterns of habitat specialization and allocation trade-offs. A phylogenetic context is vital not only to compare homologous plant traits (including defense strategies) across habitat types, but also to connect evolutionary trade-offs to patterns of species diversification in each phylogenetic lineage. We tested these predictions for trees in white-sand, clay terra firme, and seasonally flooded forests in Peru and French Guiana that represent the range of soil fertility, forest structure, and floristic compositions found throughout the Amazon region. We established 74 0.5-ha plots in these habitats and sampled all trees. Within 12 representative plots we marked newly expanding leaves of 394 saplings representing 68 species, including the most abundant species in each plot in addition to species from five focal lineages: Swartzia and Inga (Fabaceae), Protieae (Burseracaeae), Bombacoideae (Malvaceae), and Micropholis (Sapotaceae). We measured total leaf production rates for each sapling and calculated relative herbivory impact as the ratio between herbivory rate and leaf production rate. Herbivory rates averaged 2.1% per month, did not correlate with leaf production rate, and were similar across habitats. Relative herbivore impacts exceeded leaf production rates for most species. Leaf production rate averaged 2.8%, was significantly higher in seasonally flooded forests than the other two habitats, and exhibited significant correlations with specific leaf area. Species with high herbivory rates exhibited significantly lower relative abundances in terra firme forests. Overall, focal species within lineages present contrasting patterns regarding their herbivory rates and leaf production rate within habitats. These results highlight why a lineage-based approach is necessary when attempting to connect hypotheses regarding evolutionary trade-offs to community assembly patterns.
ISSN: 0012-9658

hal-01032418
https://hal.archives-ouvertes.fr/hal-01032418

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
The nine countries sharing the Amazon forest accounted for 89% of all malaria cases reported in the Americas in 2008. Remote sensing can help identify the environmental determinants of malaria transmission and their temporo-spatial evolution. Seventeen studies characterizing land cover or land use features, and relating them to malaria in the Amazon subregion, were identified. These were reviewed in order to improve the understanding of the land cover/use class roles in malaria transmission. The indicators affecting the transmission risk were summarized in terms of temporal components, landscape fragmentation and anthropic pressure. This review helps to define a framework for future studies aiming to characterize and monitor malaria.
ISSN: 1475-2875

inserm-00834790
http://www.hal.inserm.fr/inserm-00834790
http://www.hal.inserm.fr/inserm-00834790/document
http://www.hal.inserm.fr/inserm-00834790/file/1475-2875-12-192.pdf
DOI : 10.1186/1475-2875-12-192

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : Le marché de services écotouristiques se dévoile aujourd'hui comme un des principaux défis de gestion dans certains territoires protégés. Le parc amazonien Amacayacu, en Amazonie colombienne, appartient à l’un de ces territoires où le besoin d’amélioration des infrastructures de gestion et des services écotouristiques devient indispensable pour garantir la continuité de ce territoire protégé et la survie économique des groupes humains locaux. Pour cela, depuis 2005, le dispositif mis en place par le gouvernement colombien a consisté à donner en concession la gestion des services écotouristiques de ce parc au secteur privé. En premier lieu, cette recherche cherche à identifier, à tous les niveaux scalaires (local, régional, national), les étapes et les dispositifs mis en place dans ce processus de concession. En second lieu, il s’agira de mettre en évidence les impacts de ce nouveau modèle de cogestion territoriale sur les patrimoines naturels et culturels ainsi que sur les populations amérindiennes qui habitent le territoire. Enfin, nous questionnerons l’efficacité du dispositif de concession du parc Amacayacu et de ses zones de confluence, en nous attachant plus particulièrement à l’étude de la communauté Ticuna de Mocagua.
The market of ecotourism services comes to light as one of the main challenges of management in certain protected territories today. The Amazonian park Amacayacu, in Colombian Amazonia, belongs to one of these territories where the need of improvement of the infrastructures of management and the ecotourism services becomes indispensable to guarantee the continuity of management of this protected territory and the economic survival of the local human groups. For that purpose, since 2005, the device set up by the Colombian government consisted in giving in concession the management of the ecotourism services of this park to the private sector. First of all, this research tries to identify, at every level (local, regional, national), the stages and the devices set up in this process of concession. Secondly, it will be a question of bringing to light the impacts of this new model of territorial joint management on the natural and cultural heritages as well as on the Amerindian populations which live in the territory. Finally, we shall question the efficiency of the device of concession of the management of the park Amacayacu and its zones of confluence, by attaching us more particularly to the study of the community Ticuna de Mocagua.
Colombie

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.5414
http://journals.openedition.org/etudescaribeennes/5414

Éditeur(s) : HAL CCSD Wiley
Résumé : The consequences of biodiversity loss for ecosystem services largely depend on the functional identities of extirpated species. However, poor descriptions of spatial patterns of community functional composition across landscapes hamper accurate predictions, particularly in highly diverse tropical regions. Therefore, understanding how community functional composition varies across environmental gradients remains an important challenge. We sampled 15 functional traits in 800 Neotropical tree species across 13 forest plots representative of the broad climatic and soil gradients encompassed by three widespread lowland forest habitats (terra firme forests on clay-rich soils, seasonally flooded forests and white-sand forests) at opposite ends of Amazonia (Peru and French Guiana). We combined univariate and multivariate approaches to test the magnitude and predictability of environmental filtering on community leaf and wood functional composition. Directional shifts in community functional composition correlated with environmental changes across the 13 plots, with denser leaves, stems and roots in forests occurring in environments with limited water and soil-nutrient availability. Critically, these relationships allowed us to accurately predict the functional composition of 61 additional forest plots from environmental data alone.Synthesis. Environmental filtering consistently shapes the functional composition of highly diverse tropical forests at large scales across the terra firme, seasonally flooded and white-sand forests of lowland Amazonia. Environmental factors drive and allow the prediction of variation in community functional composition among habitat types in Amazonian forests.
ISSN: 0022-0477

hal-01204211
https://hal.archives-ouvertes.fr/hal-01204211
DOI : 10.1111/1365-2745.12160
PRODINRA : 259900

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Variation of dead wood decay rates among tropical trees remains one source of uncertainty in global models of the carbon cycle. Taking advantage of a broad forest plot network surveyed for tree mortality over a 23-year period, we measured the remaining fraction of boles from 367 dead trees from 26 neotropical species widely varying in wood density (0.23–1.24 g cm-3) and tree circumference at death time (31.5–272.0 cm). We modeled decay rates within a Bayesian framework assuming a first order differential equation to model the decomposition process and tested for the effects of forest management (selective logging vs. unexploited), of mode of death (standing vs. downed) and of topographical levels (bottomlands vs. hillsides vs. hilltops) on wood decay rates. The general decay model predicts the observed remaining fraction of dead wood (R2 = 60%) with only two biological predictors: tree circumference at death time and wood specific density. Neither selective logging nor local topography had a differential effect on wood decay rates. Including the mode of death into the model revealed thatstanding dead trees decomposed faster than downed dead trees, but the gain of model accuracy remains rather marginal. Overall, these results suggest that the release of carbon from tropical dead trees to the atmosphere can be simply estimated using tree circumference at death time and wood density.
ISSN: 0029-8549

hal-01094187
https://hal-agroparistech.archives-ouvertes.fr/hal-01094187
DOI : 10.1007/s00442-010-1602-8