Éditeur(s) : HAL CCSD Springer Verlag
Résumé : absent
ISSN: 0029-8549

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

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 : absent
Séminaire forêts hétérogènes du GIP ECOFOR
NA, France

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

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 : 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 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 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
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 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

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Background. In wild plant populations, genetic divergence within continuous stands is common, sometimes at very short geographical scales. While restrictions to gene flow combined with local inbreeding and genetic drift may cause neutral differentiation among subpopulations, microgeographical variations in environmental conditions can drive adaptive divergence through natural selection at some targeted loci. Such phenomena have recurrently been observed in plant populations occurring across sharp environmental boundaries, but the interplay between selective processes and neutral genetic divergence has seldom been studied.[br/]Methods. We assessed the extent of within-stand neutral and environmentally-driven divergence in the Neotropical tree [i]Eperua falcate Aubl[/i]. (Fabaceae) through a genome-scan approach. Populations of this species grow in dense stands that cross the boundaries between starkly contrasting habitats. Within-stand phenotypic and candidate-gene divergence have already been proven, making this species a suitable model for the study of genome-wide microgeographic divergence. Thirty trees from each of two habitats (seasonally flooded swamps and well-drained plateaus) in two separate populations were genotyped using thousands of AFLPs markers. To avoid genotyping errors and increase marker reliability, each sample was genotyped twice and submitted to a rigorous procedure for data cleaning, which resulted in 1196 reliable and reproducible markers.[br/]Results. Despite the short spatial distances, we detected within-populations genetic divergence, probably caused by neutral processes, such as restrictions in gene flow. Moreover, habitat-structured subpopulations belonging to otherwise continuous stands also diverge in relation to environmental variability and habitat patchiness: we detected convincing evidence of divergent selection at the genome-wide level and for a fraction of the analyzed loci (comprised between 0.25% and 1.6%). Simulations showed that the levels of differentiation for these outliers are compatible with scenarios of strong divergent selection
ISSN: 1932-6203

hal-01204220
https://hal.archives-ouvertes.fr/hal-01204220
https://hal.archives-ouvertes.fr/hal-01204220/document
https://hal.archives-ouvertes.fr/hal-01204220/file/journal.pone.0121394.PDF
PRODINRA : 287494

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : absent
ISSN: 0168-1923

hal-01032363
https://hal.archives-ouvertes.fr/hal-01032363

Éditeur(s) : HAL CCSD Wiley
Résumé : absent
ISSN: 0269-8463

hal-01032204
https://hal.archives-ouvertes.fr/hal-01032204

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : absent
ISSN: 0029-8549

hal-01032379
https://hal.archives-ouvertes.fr/hal-01032379

Éditeur(s) : HAL CCSD Wiley
Résumé : absent
ISSN: 0140-7791

hal-01032203
https://hal.archives-ouvertes.fr/hal-01032203