Éditeur(s) : HAL CCSD
Résumé : Microgeographic adaptation in tree stands. ATBC 2016
ATBC 2016
Montpellier, France

hal-01594984
https://hal.archives-ouvertes.fr/hal-01594984
PRODINRA : 365215

Éditeur(s) : HAL CCSD Ecological Society of America
Résumé : Line transect surveys are widely used in neotropical rainforests to estimate the population abundance of medium- and large-sized vertebrates. The use of indices such as Encounter Rate has been criticized because the probability of animal detection may fluctuate due to the heterogeneity of environmental conditions among sites. In addition, the morphological and behavioral characteristics (biological traits) of species affect their detectability. In this study, we compared the extent to which environmental conditions and species' biological traits bias abundance estimates in terra firme rainforests in French Guiana. The selected environmental conditions included both physical conditions and forest structure covariates, while the selected biological traits included the morphological and behavioral characteristics of species. We used the distance sampling method to model the detection probability as an explicit function of environmental conditions and biological traits and implemented a model selection process to determine the relative importance of each group of covariates. Biological traits contributed to the variability of animal detectability more than environmental conditions, which had only a marginal effect. Detectability was best for large animals with uniform or disruptive markings that live in groups in the canopy top. Detectability was worst for small, solitary, terrestrial animals with mottled markings. In the terra firme rainforests which represent ~80% of the Amazonia and Guianas regions, our findings support the use of relative indices such as the encounter rate to compare population abundance between sites in species-specific studies. Even though terra firme rainforests may appear similar between regions of Amazonia and the Guianas, comparability must be ensured, especially in forests disturbed by human activity. The detection probability can be used as an indicator of species' vulnerability to hunting and, thus, to the risk of local extinction. Only a few biological trait covariates are required to correctly estimate the detectability of the majority of medium- and large-sized vertebrates. Thus, a biological trait model could be useful in predicting the detection probabilities of rare, uncommon or localized species for which few data are available to fit the detection function.
ISSN: 1051-0761

hal-01555267
https://hal.archives-ouvertes.fr/hal-01555267
DOI : 10.1002/eap.1549
PRODINRA : 396614
PUBMED : 28419598

Éditeur(s) : HAL CCSD
International statistical ecology conference 2014
Montpellier, France

hal-01503286
https://hal-agroparistech.archives-ouvertes.fr/hal-01503286

Éditeur(s) : HAL CCSD IOP Publishing
Résumé : Tropical forests of the Guiana Shield are the most affected by gold-mining in South America,experiencing an exponential increase in deforestation since the early 2000’s.Using yearly deforestation data encompassing Guyana, Suriname, French Guiana and theBrazilian State of Amapá, we demonstrated a strong relationship between deforestation due togold-mining and gold-prices at the regional scale. In order to assess additional drivers ofdeforestation due to gold-mining, we focused on the national scale and highlighted theheterogeneity of the response to gold-prices under different political contexts. Deforestation dueto gold-mining over the Guiana Shield occurs mainly in Guyana and Suriname. On the contrary,past and current repressive policies in Amapá and French Guiana likely contribute to thedecorrelation of deforestation and gold prices. In this work, wefinally present a case studyfocusing on French Guiana and Suriname, two neighbouring countries with very different levelsof law enforcement against illegal gold-mining. We developed a modelling framework to estimatepotential deforestation leakages from French Guiana to Suriname in the border areas. Based onour assumptions, we estimated a decrease in deforestation due to gold-mining of approx. 4 300hectares in French Guiana and an increase of approx. 12 100 hectares in Suriname in response tothe active military repression of illegal gold-mining launched in French Guiana.Gold-mining in the Guiana Shield provides challenging questions regarding REDDþimplementation. These questions are discussed at the end of this study and are important topolicy makers who need to provide sustainable alternative employment to local populations inorder to ensure the effectiveness of environmental policies.
ISSN: 1748-9326

hal-01512075
https://hal.archives-ouvertes.fr/hal-01512075
https://hal.archives-ouvertes.fr/hal-01512075/document
https://hal.archives-ouvertes.fr/hal-01512075/file/document%20%2828%29_%7B81107B08-30D1-44D2-877D-32F6DFAEF28A%7D.pdf
DOI : 10.1088/1748-9326/aa6082

Éditeur(s) : HAL CCSD
Résumé : International audience
26th Biennal meeting of the Caribbean academy of sciences
Deshaies, Guadeloupe

hal-01504621
https://hal-agroparistech.archives-ouvertes.fr/hal-01504621

Éditeur(s) : HAL CCSD Wiley
Résumé :
How Quaternary climatic and geological disturbances influenced the composition of Neotropical forests is hotly debated. Rain fall and temperature changes during and/or immediately after the Last Glacial Maximum (LGM) are thought to have strongly affected the geographical distribution and local abundance of tree species. The paucity of the fossil records in Neotropical forests prevents a direct reconstruction of such processes. To describe community-level historical trends in forest composition, we turned therefore to inferential methods based on the reconstruction of past demographic changes. In particular, we modelled the history of rainforests in the Eastern Guiana Shield over a time scale of several thousand generations, through the application of Approximate Bayesian Computation (ABC) and Maximum Likelihood (ML) methods to diversity data at nuclear and chloroplast loci in eight species or subspecies of rainforest trees. Depending on the species and on the method applied, we detected population contraction, expansion or stability, with a general trend in favour of stability or expansion, with changes presumably having occurred during or after the LGM. These findings suggest that Guiana Shield rain forests have globally persisted, while expanding, through the Quaternary, but that different species have experienced different demographic events, with a trend towards the increase in frequency of light-demanding, disturbance-associated species.
ISSN: 0962-1083

hal-01512150
https://hal.archives-ouvertes.fr/hal-01512150
https://hal.archives-ouvertes.fr/hal-01512150/document
https://hal.archives-ouvertes.fr/hal-01512150/file/Barthe_et_al-_%7B0B6A8C5E-DDFF-4C4E-822C-4E7BC22A6C9B%7D.pdf
DOI : 10.1111/mec.13949

Éditeur(s) : HAL CCSD American Mosquito Control Association
Résumé : Research on natural insecticides has intensified with the spread of resistance to chemicals among insects, particularly disease vectors. To evaluate compounds, the World Health Organization (WHO) has published standardized procedures. However, those may be excessively compound-consuming when it comes to assessing the activity of natural extracts and pure compounds isolated in limited amount. As part of our work on the discovery of new mosquito larvicides from Amazonian plants, we developed a compound-saving assay in 5-ml glass tubes instead of WHO larval 100-m1 cups. Comparing activity of synthetic and natural chemicals validated the glass tube assay. Raw data, lethal doses that kill 50% (LD50) and 90% (LD90) at 24 and 48 h, were highly correlated (0.68 < R-2 < 0.96, P < 0.001, Pearson test) between cups and tubes. It was also established that 10 tubes (N = 50 larvae) provided the same level of sensitivity as 20 tubes (N= 100). This method proved suitable for rapid screening of natural extracts and molecules, identifying active compounds using 10 times less material than in the WHO protocol.
ISSN: 8756-971X

hal-01602207
https://hal.archives-ouvertes.fr/hal-01602207
DOI : 10.2987/16-6613.1
PRODINRA : 394297
PUBMED : 28206865

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : We examined tree-soil habitat associations in lowland forest communities at Paracou, French Guiana. We analyzed a large dataset assembling six permanent plots totaling 37.5 ha, in which extensive LIDAR-derived topographical data and soil chemical and physical data have been integrated with precise botanical determinations. Map of relative elevation from the nearest stream summarized both soil fertility and hydromorphic characteristics, with seasonally inundated bottomlands having higher soil phosphate content and base saturation, and plateaus having higher soil carbon, nitrogen and aluminum contents. We employed a statistical test of correlations between tree species density and environmental maps, by generating Monte Carlo simulations of random raster images that preserve autocorrelation of the original maps. Nearly three fourths of the 94 taxa with at least one stem per ha showed a significant correlation between tree density and relative elevation, revealing contrasted species-habitat associations in term of abundance, with seasonally inundated bottomlands (24.5% of species) and well-drained plateaus (48.9% of species). We also observed species preferences for environments with or without steep slopes (13.8% and 10.6%, respectively). We observed that closely-related species were frequently associated with different soil habitats in this region (70% of the 14 genera with congeneric species that have a significant association test) suggesting species-habitat associations have arisen multiple times in this tree community. We also tested if species with similar habitat preferences shared functional strategies. We found that seasonally inundated forest specialists tended to have smaller stature (maximum diameter) than species found on plateaus. Our results underline the importance of tree-soil habitat associations in structuring diverse communities at fine spatial scales and suggest that additional studies are needed to disentangle community assembly mechanisms related to dispersal limitation, biotic interactions and environmental filtering from species-habitat associations. Moreover, they provide a framework to generalize across tropical forest sites.
ISSN: 1932-6203

hal-01260289
https://hal.archives-ouvertes.fr/hal-01260289
PRODINRA : 342930
DOI : 10.1371/journal.pone.0141488

Éditeur(s) : HAL CCSD
Résumé : International audience
Evoluzione 2013. 5th congress of the Italian Society for Evolutionary Biology, Italie, 28-30 août
Trento, Italy

hal-01627541
https://hal.archives-ouvertes.fr/hal-01627541

Éditeur(s) : HAL CCSD Elsevier
Résumé : While around 20% of the Amazonian forest has been cleared for pastures and agriculture, one fourth of the remaining forest is dedicated to wood production [1] . Most of these production forests have been or will be selectively harvested for commercial timber, but recent studies show that even soon after logging, harvested stands retain much of their tree-biomass carbon and biodiversity [2,3] . Comparing species richness of various animal taxa among logged and unlogged forests across the tropics, Burivalova et al. [4] found that despite some variability among taxa, biodiversity loss was generally explained by logging intensity (the number of trees extracted). Here, we use a network of 79 permanent sample plots (376 ha total) located at 10 sites across the Amazon Basin [5] to assess the main drivers of time-to-recovery of post-logging tree carbon ( Table S1 ). Recovery time is of direct relevance to policies governing management practices (i.e., allowable volumes cut and cutting cycle lengths), and indirectly to forest-based climate change mitigation interventions.
ISSN: 0960-9822

hal-01536542
https://hal.archives-ouvertes.fr/hal-01536542
DOI : 10.1016/j.cub.2015.07.034
PRODINRA : 343217
PUBMED : 26394096

Éditeur(s) : HAL CCSD Elsevier
Résumé :  
The present chapter first provides a general overview of Paracou experimental site within the ecological context of French Guiana and describes the original design of Silvicultural Project and the main data collected on the plots. It then review the main characteristics and potential differences between these plots, as a basis for further discussion and interpretation of the results reported in some of the following chapters.
Ecology and management of a neotropical rainforest: lessons drawn from Paracou, a long-term experimental research site in French Guiana

ISBN : 2-84299-455-8
hal-01189542
https://hal.archives-ouvertes.fr/hal-01189542
PRODINRA : 46424

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : Architectural analyses of temperate tree species using a chronological approach suggest that the expression of epicormic branches is closely related to low growth rates in the axes that make up the branching system. Therefore, sole consideration of epicormic criteria may be sufficient to identify trees with low secondary growth levels or with both low primary and secondary growth levels. In a tropical tree such as Dicorynia guianensis (basralocus), where chronological studies are difficult, this relationship could be very useful as an easily accessible indicator of growth potentials. A simple method of architectural tree description was used to characterize the global structure of more than 1650 basralocus trees and to evaluate their growth level. Measurements of simple growth characters [height, basal diameter, internode length of submittal part (top of the main axis of the tree)] and the observation of four structural binary descriptors on the main stem (presence of sequential branches and young epicormic branches, state of the submittal part, global orientation), indicated that epicormic branch formation is clearly related to a decrease in length of the successive growth units of the main stem. Analysis of height vs. diameter ratios among different tree subgroups, with and without epicormic branching, suggested that trees with epicormic branches generally have a low level of secondary growth compared with primary growth.
ISSN: 0305-7364

hal-01032037
https://hal.archives-ouvertes.fr/hal-01032037
DOI : 10.1093/aob/mcg119

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve agro-ecosystem sustainability. We assessed soil carbon mass changes in a sandy-clayey and well-drained soil in French Guiana after forest clearing by the chop-and-mulch method and crop establishment. At the experimental site of Combi, native forest was cut down in October 2008; woody biomass was chopped and incorporated into the top 20 cm of soil. After about one year of legume and grass cover, three forms of land management were compared: grassland (Urochloa ruziziensis), maize/soybean crop rotation with disk tillage and in direct seeding without tillage. There were four replicates. We measured 14.16 kg m(-2) of carbon in 2 mm-sieved soil down to 2 m depth for the initial forest. Forest clearing did not induce significant soil compaction; neither did any specific agricultural practice. In converted soils, C stocks were measured in the 0-30 cm layer after each crop for three years. Carbon mass changes for soil fractions <2 mm (soil C stock) and >2 mm (soil C pool) in the 0-5, 5-10, 10-20 and 20-30 cm soil layers were assessed on an equivalent soil mass basis. One year and 1.5 years after deforestation, higher C stocks (+0.64 to 1.16 kg C m(-2) yr(-1)) and C pools (+0.52 to 0.90 kg C m(-2) yr(-1)) were measured in converted soils, compared to those of the forest into the top 30 cm of soil. However, the masses of carbon in these converted soils declined later. The highest rates of carbon decrease were measured between 1.5 and 2 years after forest conversion in the <2 mm soil fraction, from 0.46 kg Cm-2 yr(-1) (in grassland soils) to 0.71 kg C m(-2) yr(-1) (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41 kg C m(-2) yr(-1) (cropland under disk tillage) to 0.76 kg C m(-2) yr(-1) (grassland soils). Three years after forest conversion, C masses in the top 30 cm of soils for grassland showed similar values than for forest. In comparison, the carbon stock in cropped soils managed under no tillage in direct seeding (without mulch) was significantly 17% and 16% lower than in forest and grassland soils, respectively. None of the studied agricultural practices succeeded in accumulating carbon from the chopped forest biomass.
ISSN: 0167-8809

hal-01032438
https://hal.archives-ouvertes.fr/hal-01032438
DOI : 10.1016/j.agee.2013.11.009

Éditeur(s) : HAL CCSD Hindawi Publishing Corporation
Résumé : International audience
We generalize Ripley's K function to get a new function, M, to characterize the spatial structure of a point pattern relatively to another one. We show that this new approach is pertinent in ecology when space is not homogenous and the size of objects matters. We present how to use the function and test the data against the null hypothesis of independence between points. In a tropical tree data set we detect intraspecific aggregation and interspecific competition.
ISSN: 1687-9708

hal-01502623
https://hal-agroparistech.archives-ouvertes.fr/hal-01502623
DOI : 10.1155/2012/619281

Éditeur(s) : HAL CCSD Editions Quae
Résumé :  
absent
De l'observation des écosystèmes forestiers à l'information sur la forêt
Paris, France

hal-01032065
https://hal.archives-ouvertes.fr/hal-01032065

Éditeur(s) : HAL CCSD Wiley
Résumé :  
absent
ISSN: 0307-6946

hal-01032107
https://hal.archives-ouvertes.fr/hal-01032107
DOI : 10.1111/j.1365-2311.2011.01265.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : Understanding the pattern in spatial distribution of soil microbial processes is critical to understand the environmental factors that regulate them as well as to scale up these processes to ecosystem. Soil samples from a I ha tropical rainforest plot (Paracou, French Guiana) were analyzed according a nested sampling approach using different separation distances ranging from 0.4 to 40 m. The variability of substrate induced respiration (SIR) and of denitrification enzyme activity (DEA) was characterized in relation to various soil properties (total C and N contents, NIRS related index of soil organic matter quality, SOMQ and index of tree influence potential, IP). The variability of SIR and DEA was higher than that of environmental properties. The patterns of accumulated variance as a function of distance varied among the soil properties. The variability of SIR and DEA mainly occurred at small (1 m) scale (and at the 10-40 m-scales for SIR), probably reflecting the quality of litter input that results of the influence of local assemblage of different tree species, though changes in the soil N and C contents. Indeed, total soil C and N contents explained the microbial properties at every scale. Coefficients of codispersion showed that neither SOMQ nor IP did correlate with SIR and DEA, and confirmed that total C and N contents explained microbial properties in a scale dependent and complex manner. Such spatial dependency underlines the importance of soil heterogeneity in this tropical forest with implications for sampling strategies when studying the microbial processes and their response to disturbances. (C) 2012 Elsevier B.V. All rights reserved.
ISSN: 0016-7061

hal-01032409
https://hal.archives-ouvertes.fr/hal-01032409
DOI : 10.1016/j.geoderma.2012.12.009

Éditeur(s) : HAL CCSD
Résumé : Genetic structure of Hylesia metabus (Lepidoptera: Saturniidae), moths responsible for lepidopterism outbreaks in French Guiana and Venezuela. . ICE 2016; XXV International Congress of Entomology
ICE 2016; XXV International Congress of Entomology
Orlando, United States

hal-01607289
https://hal.archives-ouvertes.fr/hal-01607289
DOI : 10.1603/ICE.2016.113657
PRODINRA : 396124

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Ethnopharmacological relevancePsidium acutangulum Mart. ex DC is a small tree used by the Wayana Amerindians from the Upper-Maroni in French Guiana for the treatment of malaria.Aim of the studyIn a previous study, we highlighted the in vitro antiplasmodial, antioxidant and anti-inflammatory potential of the traditional decoction of P. acutangulum aerial parts. Our goal was then to investigate on the origin of the biological activity of the traditional remedy, and eventually characterize active constituents.Materials and methodsLiquid-liquid extractions were performed on the decoction, and the antiplasmodial activity evaluated against chloroquine-resistant FcB1 ([3H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains, and on a chloroquine sensitive NF54 ([3H]-hypoxanthine bioassay) P. falciparum strain. The ethyl acetate fraction (D) was active and underwent bioguided fractionation. All the isolated compounds were tested on P. falciparum FcB1 strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) of the ethyl acetate fraction and of an anti-Plasmodium active compound, was concurrently assessed on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the fractions and pure compounds was measured on VERO cells, L6 mammalian cells, PBMCs, and RAW cells.ResultsFractionation of the ethyl acetate soluble fraction (IC50 ranging from 3.4 to <1 µg/mL depending on the parasite strain) led to the isolation of six pure compounds: catechin and five glycosylated quercetin derivatives. These compounds have never been isolated from this plant species. Two of these compounds (wayanin and guaijaverin) were found to be moderately active against P. falciparum FcB1 in vitro (IC50 5.5 and 6.9 µM respectively). We proposed the name wayanin during public meetings organized in June 2015 in the Upper-Maroni villages, in homage to the medicinal knowledge of the Wayana population. At 50 µg/mL, the ethyl acetate fraction (D) significantly inhibited IL-1β secretion (−46%) and NO production (−21%), as previously observed for the decoction. The effects of D and guiajaverin (4) on the secretion of other cytokines or NO production were not significant.ConclusionsThe confirmed antiplasmodial activity of the ethyl acetate soluble fraction of the decoction and of the isolated compounds support the previous results obtained on the P. acutangulum decoction. The antiplasmodial activity might be due to a mixture of moderately active non-toxic flavonoids. The anti-inflammatory activities were less marked for ethyl acetate fraction (D) than for the decoction.
ISSN: 0378-8741

hal-01313006
http://hal.upmc.fr/hal-01313006
http://hal.upmc.fr/hal-01313006/document
http://hal.upmc.fr/hal-01313006/file/Houel_Wayanin_and.pdf
DOI : 10.1016/j.jep.2016.04.053

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
ISSN: 1631-0691

hal-01083754
https://hal-agroparistech.archives-ouvertes.fr/hal-01083754
DOI : 10.1016/j.crvi.2009.01.006