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 Nature Publishing Group
Résumé : While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few 'hyperdominant' species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region.
ISSN: 2041-1723

hal-01204225
https://hal.archives-ouvertes.fr/hal-01204225
DOI : 10.1038/ncomms7857
PRODINRA : 305614
PUBMED : 25919449

Éditeur(s) : HAL CCSD
Résumé : absent
Séminaire forêts hétérogènes du GIP ECOFOR
NA, France

hal-01269340
https://hal.archives-ouvertes.fr/hal-01269340
PRODINRA : 331590

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
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 Springer Verlag
Résumé : absent
ISSN: 0029-8549

hal-01032202
https://hal.archives-ouvertes.fr/hal-01032202

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
We conducted a survey along three belt transects located at increasing distances from the coast to determine whether a non-random arboreal ant assemblage, such as an ant mosaic, exists in the rainforest on the Masoala Peninsula, Madagascar. In most tropical rainforests, very populous colonies of territorially dominant arboreal ant species defend absolute territories distributed in a mosaic pattern. Among the 29 ant species recorded, only nine had colonies large enough to be considered potentially territorially dominant; the remaining species had smaller colonies and were considered non-dominant. Nevertheless, the null-model analyses used to examine the spatial structure of their assemblages did not reveal the existence of an ant mosaic. Inland, up to 44% of the trees were devoid of dominant arboreal ants, something not reported in other studies. While two Crematogaster species were not associated with one another, Brachymyrmex cordemoyi was positively associated with Technomyrmex albipes, which is considered an invasive species-a non-indigenous species that has an adverse ecological effect on the habitats it invades. The latter two species and Crematogaster ranavalonae were mutually exclusive. On the other hand, all of the trees in the coastal transect and at least 4 km of coast were occupied by T. albipes, and were interconnected by columns of workers. Technomyrmex albipes workers collected from different trees did not attack each other during confrontation tests, indicating that this species has formed a supercolony along the coast. Yet interspecific aggressiveness did occur between T. albipes and Crematogaster ranavalonae, a native species which is likely territorially dominant based on our intraspecific confrontation tests. These results suggest that the Masoala rainforest is threatened by a potential invasion by T. albipes, and that the penetration of this species further inland might be facilitated by the low density of native, territorially dominant arboreal ants normally able to limit its progression.
ISSN: 1932-6203

hal-00817444
https://hal.archives-ouvertes.fr/hal-00817444
https://hal.archives-ouvertes.fr/hal-00817444/document
https://hal.archives-ouvertes.fr/hal-00817444/file/Dejean2010_Spatial.pdf
DOI : 10.1371/journal.pone.0009319

Éditeur(s) : HAL CCSD CRC Press
Résumé : Among the ecosystem services provided by forests, wood provisioning takes a central position. Wood and derived products have played a critical role in the evolution of human kind and demand for raw material is increasing in a foreseeable future. Wood is used for energy production, construction and a wide variety of products for which different properties are required. Anatomical, chemical and physical properties of wood are determined through a complex process called xylogenesis controlled by internal and external signals and occurring during the life of the tree. In this chapter we describe i/how wood is formed and ii/the different factors controlling this developmental process with emphasis on the molecular machinery involved, iii/the functions of wood and iv/the biotechnology approaches developed to improve wood biomass production and properties genetically.
Tree Biotechnology

ISBN : 978-1466597143
hal-01032436
https://hal.archives-ouvertes.fr/hal-01032436

Éditeur(s) : HAL CCSD Elsevier
Résumé : absent
ISSN: 0034-4257

hal-01019844
https://hal.archives-ouvertes.fr/hal-01019844
DOI : 10.1016/j.rse.2012.03.012

Éditeur(s) : HAL CCSD Wiley
Résumé : 1. Considerable debate surrounds the extent to which tropical forests can be managed for resource extraction while conserving biodiversity and ecosystem properties, which depend on functional composition. Here we evaluate the compatibility of these aims by examining the effects of logging on taxonomic and functional diversity and composition in a tropical forest. 2. Twenty years after selective logging, we inventoried 4140 stems regenerating in logging gaps and adjacent undisturbed areas, and we integrated a database of 13 functional traits describing leaf and wood economics of tropical trees. 3. We found no differences in taxonomic and functional richness among habitats, but logging gaps had significantly higher taxonomic and functional evenness. 4. Logging also effected striking, long-term changes in both species and functional composition. In particular, the xylem density of recruits in logging gaps was 6% less than in unlogged forests, leaves were 11% less tough and had 613% greater mineral nutrient concentrations. 5. Synthesis and applications. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand.
ISSN: 0021-8901

hal-01032420
https://hal.archives-ouvertes.fr/hal-01032420
DOI : 10.1111/j.1365-2664.2012.02164.x

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
ISSN: 1354-1013

hal-01080954
https://hal-agroparistech.archives-ouvertes.fr/hal-01080954
DOI : 10.1111/j.1365-2486.2007.01439.x

Éditeur(s) : HAL CCSD
Résumé : International audience
Trees can control their shape and resist gravity thanks to their ability to produce wood under tensile stress. This stress is known to be produced during the maturation of wood fibres but the mechanism of its generation remains unclear. This study focuses on the formation of the secondary wall in tension wood produced in artificially tilted poplar saplings. Thickness of secondary wall layer (SL) and gelatinous layer (GL) were measured from cambium to mature wood in several trees sampled at different times after tilting. Measurements on wood fibres produced before tilting show the progressive increase of secondary wall thickness during the growing season. After the tilting date, SL thickness decreased markedly from normal wood to tension wood while the total thickness increased compared to normal wood, with the development of a thick GL. However, even after GL formation, SL thickness continues to increase during the growing season. GL thickening was observed to be faster than SL thickening. The development of the unlignified GL is proposed to be a low cost, efficient strategy for a fast generation of tensile stress in broadleaved trees.
IAWA journal / International Association of Wood Anatomists.

hal-01229277
https://hal.archives-ouvertes.fr/hal-01229277
https://hal.archives-ouvertes.fr/hal-01229277/document
https://hal.archives-ouvertes.fr/hal-01229277/file/AbediniClair-Iawa-TensionCellWallThickening_preprint_HAL.pdf
DOI : 10.1163/22941932-00000084

Éditeur(s) : HAL CCSD INRA Editions
Résumé : International audience
The objective of this study was to examine the water relations and hydraulic architecture and vulnerability to cavitation in Virola surinamensis and V. michelii and to compare to similar measurements in Eperua falcata. In several previous reports Virola was seen to have a rather narrow range of xylem pressure potentials (Ψx) near zero in the course of a wet-season day while having water fluxes quite close to Eperua. We tested the hypothesis that the narrow range of Ψx might be consistent with very high hydraulic conductivities of stems, roots and shoots and high vulnerability to cavitation in Virola compared to Eperua. When this hypothesis proved false we concluded that the previous determinations of Ψx might be wrong in Virola due to latex. We re-examined the determination of Ψx in Virola by the pressure chamber technique and compared results to determination of Ψleaf by the thermocouple psychrometer technique and found that the likely range of Ψx are more negative than previously reported. Problems concerning the determination of Ψx in species with latex are discussed.
ISSN: 2268-4565

hal-01077475
https://hal.archives-ouvertes.fr/hal-01077475
https://hal.archives-ouvertes.fr/hal-01077475/document
https://hal.archives-ouvertes.fr/hal-01077475/file/JPH-1-e0002.pdf

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Functional aspects of biodiversity were investigated in a lowland tropical rainforest in French Guyana (5°2'N, annual precipitation 2200 mm). We assessed leaf '15N as a presumptive indicator of symbiotic N2 fixation, and leaf and wood cellulose '13C as an indicator of leaf intrinsic water-use efficiency (CO2 assimilation rate/leaf conductance for water vapour) in dominant trees of 21 species selected for their representativeness in the forest cover, their ecological strategy (pioneers or late successional stage species, shade tolerance) or their potential ability for N2 fixation. Similar measurements were made in trees of native species growing in a nearby plantation after severe perturbation (clear cutting, mechanical soil disturbance). Bulk soil '15N was spatially quite uniform in the forest (range 3-5‰), whereas average leaf '15N ranged from m0.3‰ to 3.5‰ in the different species. Three species only, Diplotropis purpurea, Recordoxylon speciosum (Fabaceae), and Sclerolobium melinonii (Caesalpiniaceae), had root bacterial nodules, which was also associated with leaf N concentrations higher than 20 mg gm1. Although nodulated trees displayed significantly lower leaf '15N values than non-nodulated trees, leaf '15N did not prove a straightforward indicator of symbiotic fixation, since there was a clear overlap of '15N values for nodulated and non-nodulated species at the lower end of the '15N range. Perturbation did not markedly affect the difference '15Nsoil m '15Nleaf, and thus the isotopic data provide no evidence of an alteration in the different N acquisition patterns. Extremely large interspecific differences in sunlit leaf '13C were observed in the forest (average values from m31.4 to m26.7‰), corresponding to intrinsic water-use efficiencies (ratio CO2 assimilation rate/leaf conductance for water vapour) varying over a threefold range. Wood cellulose '13C was positively related to total leaf '13C, the former values being 2-3‰ higher than the latter ones. Leaf '13C was not related to leaf '15N at either intraspecific or interspecific levels. '13C of sunlit leaves was highest in shade hemitolerant emergent species and was lower in heliophilic, but also in shade-tolerant species. For a given species, leaf '13C did not differ between the pristine forest and the disturbed plantation conditions. Our results are not in accord with the concept of existence of functional types of species characterized by common suites of traits underlying niche differentiation; rather, they support the hypothesis that each trait leads to a separate grouping of species.
ISSN: 0029-8549

hal-01032378
https://hal.archives-ouvertes.fr/hal-01032378
DOI : 10.1007/s004420050593

Éditeur(s) : HAL CCSD Oxford University Press (OUP): Policy B - Oxford Open Option B
Résumé : absent
ISSN: 0829-318X

hal-01032253
https://hal.archives-ouvertes.fr/hal-01032253

Éditeur(s) : HAL CCSD Elsevier
Résumé : Vegetation phenology is the study of the timing of seasonal events that are considered to be the result of adaptive responses to climate variations on short and long time scales. In the field of remote sensing of vegetation phenology, phenological metrics are derived from time series of optical data. For that purpose, considerable effort has been specifically focused on developing noise reduction and cloud-contaminated data removal techniques to improve the quality of remotely-sensed time series. Comparative studies between time series composed of satellite data acquired under clear and cloudy conditions and from radiometric data obtained with high accuracy from ground-based measurements constitute a direct and effective way to assess the operational use and limitations of remote sensing for predicting the main plant phenological events. In the present paper, we sought to explicitly evaluate the potential use of MODerate resolution Imaging Spectroradiometer (MODIS) remote sensing data for monitoring the seasonal dynamics of different types of vegetation cover that are representative of the major terrestrial biomes, including temperate deciduous forests, evergreen forests, African savannah, and crops. After cloud screening and filtering, we compared the temporal patterns and phenological metrics derived from in situ NDVI time series and from MODIS daily and 16-composite products. We also evaluated the effects of residual noise and the influence of data gaps in MODIS NDVI time series on the identification of the most relevant metrics for vegetation phenology monitoring. The results show that the inflexion points of a model fitted to a MODIS NDVI time series allow accurate estimates of the onset of greenness in the spring and the onset of yellowing in the autumn in deciduous forests (RMSE <= one week). Phenological metrics identical to those provided with the MODIS Global Vegetation Phenology product (MDC12Q2) are less robust to data gaps, and they can be subject to large biases of approximately two weeks or more during the autumn phenological transitions. In the evergreen forests, in situ NDVI time series describe the phenology with high fidelity despite small temporal changes in the canopy foliage. However, MODIS is unable to provide consistent phenological patterns. In crops and savannah, MODIS NDVI time series reproduce the general temporal patterns of phenology, but significant discrepancies appear between MODIS and ground-based NDVI time series during very localized periods of time depending on the weather conditions and spatial heterogeneity within the MODIS pixel. In the rainforest, the temporal pattern exhibited by a MODIS 16-day composite NDVI time series is more likely due to a pattern of noise in the NDVI data structure according to both rainy and dry seasons rather than to phenological changes. More investigations are needed, but in all cases, this result leads us to conclude that MODIS time series in tropical rainforests should be interpreted with great caution. (C) 2013 Elsevier Inc. All rights reserved.
ISSN: 0034-4257

hal-01032407
https://hal.archives-ouvertes.fr/hal-01032407
DOI : 10.1016/j.rse.2013.01.010

Éditeur(s) : HAL CCSD
Résumé : More than 15% of Amazon forest has been converted to pastures these last decades. Some authors argued the world’s permanent pastures (30 % of total land) could potentially offset up to 4% of the global GHG emissions, having a carbon (C) storage potential equal to 0.5 Mg C.ha-1.yr-1(Schulze et al 2009). Accordingly, pastures are good candidates to increase soil uptake C in soil while ensuring a basic food production. Here we would like to assess the effects of tropical forest conversion to cattle pasture in the French Amazonia (French Guiana), by following the long-term dynamics of soil C stocks of permanent tropical pastures (Brachiaria humidicola) after deforestation from 1970. A soil inventory campaign was performed to analyse soil C and N stocks (to 1 m depth) along a pasture chronosequence of 6 months to 36 years old pastures and 4 native forest sites (total 24 sites). The annual C sequestration potential demonstrated by the chronosequence, was compared with eddy covariance flux measurements on 2 pastures and one native forest. Our study shows that old (≥ 24 years) tropical pastures resettle the recurrent C storage observed in native forest. These pastures stored between 1.8 ± 0.5 and 5.3 ± 2.1 tC ha-1 yr-1 compared with 2.6 ± 0.5 tC ha-1 yr-1 for the nearby native forest. Our finding show that old tropical pastures accumulate carbon in soil organic matter, particularly in the deep soil layers (0.2-1 m) and without loss of soil fertility. It suggests that such pastures can be exploited by farmers in the long term with appropriate practices (no fire and no overgrazing, but a mixture of grasses and legumes and a grazing rotation plan). Clearly, efforts to curb deforestation are a priority in order to preserve forest biodiversity and C stocks. But it seems now that, in a climate-smart agriculture way, the current challenge is to manage these deforested areas to maintain the productivity of agricultural ecosystems and in the same time their capacity to mitigate GES.
Building tomorrow’s research agenda and bridging the science-policy gap
Montpellier, France

hal-01204231
https://hal.archives-ouvertes.fr/hal-01204231
PRODINRA : 324147

Éditeur(s) : HAL CCSD CRC Press
Résumé : Among the ecosystem services provided by forests, wood provisioning takes a central position. Wood and derived products have played a critical role in the evolution of human kind and demand for raw material is increasing in a foreseeable future. Wood is used for energy production, construction and a wide variety of products for which different properties are required. Anatomical, chemical and physical properties of wood are determined through a complex process called xylogenesis controlled by internal and external signals and occurring during the life of the tree. In this chapter we describe i/how wood is formed and ii/the different factors controlling this developmental process with emphasis on the molecular machinery involved, iii/the functions of wood and iv/the biotechnology approaches developed to improve wood biomass production and properties genetically.
Tree Biotechnology

ISBN : 9781466597143
hal-01204210
https://hal.archives-ouvertes.fr/hal-01204210
PRODINRA : 257126

Éditeur(s) : HAL CCSD
Résumé : Couche G ou couche tertiaire : quel nom pour la couche interne des fibres du bois de tension ?. 11es Journées du Réseau Français des Parois
11es Journées du Réseau Français des Parois
Orléans, France

hal-01603178
https://hal.archives-ouvertes.fr/hal-01603178
PRODINRA : 398652

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1).
ISSN: 1726-4170

hal-01557759
https://hal.univ-lorraine.fr/hal-01557759
https://hal.univ-lorraine.fr/hal-01557759/document
https://hal.univ-lorraine.fr/hal-01557759/file/bg-13-2537-2016.pdf
DOI : 10.5194/bg-13-2537-2016