Résumé
Investigations of basic radial wood den- sity (WD) in tropical trees revealed linear patterns and some curvilinear patterns. Studies usually disregard longitudinal variations, which are often considered to be similar to radial variations. This study aimed to show (1) a new radial curvilinear WD pattern, (2) differences in amplitude between radial and longi- tudinal gradients and (3) to partition WD variations according to different scales in Parkia velutina , an emergent tree found in Neotropical rain forests. We collected full discs from six felled trees and radial cores from 10 standing trees to check WD variability, plus one dominant axis per tree for analysis of height growth rates. This species showed very high growth rates indicative of heliophilic habits. WD varied from 0.194 to 0.642 g/cm 3 . Such amplitude is rarely observed within the same tree. Radial variation in WD was curvilinear, with an amplitude generally less than the longitudinal amplitude. Consequently, in mature trees, WD values in the crown were higher than those in the outer trunk. WD variations can be highly significant at different scales. The variance partitioning also revealed that the whole WD range of Parkia velutina is more accurately estimated intra-indivi- dually when both longitudinal and radial gradient are covered
Auteurs, date et publication :
Auteurs Hélène Morel , Romain Lehnebach , Jérémy Cigna , Julien Ruelle , Eric Nicolini , Jacques Beauchêne
Publication : Bois et Forêts des Tropiques
Date : 2025
Volume : 335
Pages : 59–69
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs J. - M. Floch , E. Marcon , F. Puech , V. Loonis , M. - P. de Bellefon
Date : 2025
Pages : 71–111
Catégorie(s)
#CIRAD #FORET ParacouRésumé
© 2018, INRA and Springer-Verlag France SAS, part of Springer Nature. Key message: The natural durability ofDicorynia guianensis Amsh's Heartwood is conferred by the high content of antioxidant phenolic compounds, especially tannins and flavonoids combined with the presence of fungistatic alkaloids. The content of phenolic compounds increases according to the natural durability classes, from durable wood (class 2) to moderately durable wood (class 3) and correlated to the antioxidant capacity. Context: The heartwood of Dicorynia guianensis Amsh is resistant to white rot fungi decay, but the mechanism of this natural durability is not fully elucidated. Aims: Biochemical studies were carried out in order to better understand the role of extractives in natural durability of D. guianensis. Methods: The powders from durable and moderately durable heartwood were extracted with methanol, ethanol, and hot water. The quantity of total phenols, tannins, and flavonoids as well as antioxidant activity, evaluated by 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) were determined using colorimetric methods. Antifungal activity was assessed by using two white rot fungi. The bioactive fractions and compounds were obtained using bio-guided fractionation, HPLC isolation, MS and RMN spectroscopic analyses. Results: Durable woods contain higher amounts of heartwood extract and antioxidant activity. Antioxidant activity was highly correlated with the content of phenolics. The purification of the most antioxidant fraction FII affords the characterization of (+)-catechin (−)-epicatechin, neoastilbin, astilbin, and isoastilbin. Alkaloid fraction FIII exhibits dose-dependent fungistatic activity against Pycnoporus sanguineus Linnaeus and Trametes versicolor Quelet. Conclusion: Phenolic antioxidants and fungistatic alkaloids positively impact the natural durability of D. guianensis.
Auteurs, date et publication :
Auteurs Jean Baptiste Say Anouhe , Florence Bobelé Niamké , Milcard Faustin , David Virieux , Jean Luc Pirat , Augustin Amissa Adima , Seraphin Kati-Coulibaly , Nadine Amusant
Publication : Annals of Forest Science
Date : 2018
Volume : 75
Issue : 1
Pages : 15
Catégorie(s)
#CIRAD #FORET ParacouRésumé
1.”What controls the distribution and abundance of organisms”? This question, at the heart of the dynamics of ecological communities, would have been familiar to the earliest ecologists. Having lain effectively abandoned for many years, community dynamics today is a vibrant research topic of great conceptual interest with practical import for conservation, ecological management, ecosystem services and the responses of ecological communities to climate change. 2.We describe how modern coexistence theory can be applied to predict community dynamics through the use of demography. We explore the challenges that limit the deployment of this demographic framework, and the tools from phylogenetic and functional ecology that have been used to surmount them. 3.Finding existing tools not altogether sufficient, we propose the use of ‘hard' functional traits and physiological tolerances of environmental conditions and low resource availability to extend the demographic framework so that the dynamics of a broader range of ecological communities can be accurately predicted. 4.We illustrate these new approaches with two case studies. Given the urgent need to accurately forecast the dynamics of ecological communities, we hope that many ecologists will adopt these tools.
Auteurs, date et publication :
Auteurs C. E. Timothy Paine , Anna Deasey , A. Bradley Duthie
Publication : Functional Ecology
Date : 2018
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Soil nutrient availability has a strong influence on the fate of soil carbon (C) during microbial decomposition, contributing to Earth's C balance. While nutrient availability itself can impact microbial physiology and C partitioning between biomass and respiration during soil organic matter decomposition, the availability of labile C inputs may mediate the response of microorganisms to nutrient additions. As soil organic matter is decomposed, microorganisms retain or release C, nitrogen (N) or phosphorus (P) to maintain a stoichiometric balance. Although the concept of a microbial stoichiometric homeostasis has previously been proposed, microbial biomass CNP ratios are not static, and this may have very relevant implications for microbial physiological activities. Here, we tested the hypothesis that N, P and potassium (K) nutrient additions impact C cycling in a tropical soil due to microbial stoichiometric constraints to growth and respiration, and that the availability of energy-rich labile organic matter in the soil (i.e. leaf litter) mediates the response to nutrient addition. We incubated tropical soil from French Guiana with a 13C labeled leaf litter addition and with mineral nutrient additions of +K, +N, +NK, +PK and +NPK for 30 days. We found that litter additions led to a ten-fold increase in microbial respiration and a doubling of microbial biomass C, along with greater microbial N and P content. We found some evidence that P additions increased soil CO2 fluxes. Additionally, we found microbial biomass CP and NP ratios varied more widely than CN in response to nutrient and organic matter additions, with important implications for the role of microorganisms in C cycling. The addition of litter did not prime soil organic matter decomposition, except in combination with +NK fertilization, indicating possible P-mining of soil organic matter in this P-poor tropical soil. Together, these results point toward an ultimate labile organic substrate limitation of soil microorganisms in this tropical soil, but also indicate a complex interaction between C, N, P and K availability. This highlights the difference between microbial C cycling responses to N, P, or K additions in the tropics and explains why coupled C, N and P cycle modeling efforts cannot rely on strict microbial stoichiometric homeostasis as an underlying assumption.
Auteurs, date et publication :
Auteurs Jennifer L. Soong , Sara Marañon-Jimenez , M. Francesca Cotrufo , Pascal Boeckx , Samuel Bodé , Bertrand Guenet , Josep Peñuelas , Andreas Richter , Clément Stahl , Erik Verbruggen , Ivan A. Janssens
Publication : Soil Biology and Biochemistry
Date : 2018
Volume : 122
Pages : 141–149
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Driven by a necessity for confident molecular identification at high spatial resolution, a new time-of-flight secondary ion mass spectrometry (TOF-SIMS) tandem mass spectrometry (tandem MS) imaging instrument has been recently developed. In this report, the superior MS/MS spectrometry and imaging capability of this new tool is shown for natural product study. For the first time, via in situ analysis of the bioactive metabolites rubrynolide and rubrenolide in Amazonian tree species Sextonia rubra (Lauraceae), we were able both to analyze and to image by tandem MS the molecular products of natural biosynthesis. Despite the low abundance of the metabolites in the wood sample(s), efficient MS/MS analysis of these γ-lactone compounds was achieved providing high confidence in the identification and localization. In addition, tandem MS imaging minimized the mass interferences and revealed specific localization of these metabolites primarily in the ray paren-chyma cells but also in certain oil cells and, further,...
Auteurs, date et publication :
Auteurs Tingting Fu , David Touboul , Serge Della-Negra , Emeline Houël , Nadine Amusant , Christophe Duplais , Gregory L Fisher , Alain Brunelle
Publication : Analytical Chemistry
Date : 2018
Pages : acs.analchem.8b01157
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Polarimetric Synthetic Aperture Radar Interferometry (PolInSAR) has shown potential for the retrieval of a forest canopy height model (CHM) and the underlying solid earth digital terrain model (DTM). However, because of non-volume decorrelation and other unavoidable errors, the robustness of retrieval heights is sensitive to the spatial baseline of the selected InSAR pairs, which relates forest parameters to measured coherence. Within the context of the random volume over ground (RVoG) model and the three-stage inversion method, we aimed to quantify the influence of spatial baseline on the inversions at P-band, which are distinct from the inversions at higher frequency due to the non-negligible ground contributions. This information assists in optimal baseline selection and the development of robust inversion schemes. Assumptions about the extinction coefficient and additional DTM or DEM were used to reduce the influence of ground contribution on CHM and DTM inversion, respectively. Inversions from published airborne repeat-pass P-band PolInSAR data with four different spatial baselines were validated against LiDAR-derived DTM and CHM data. The results show that a longer spatial baseline performed better in DTM inversion. The longest baseline produced the best R2 of 0.995 and RMSE of 0.555 m, much better than the smallest baseline with an R2 of 0.794 and RMSE of 3.74 m. A threshold height could be identified that determines the overestimation and underestimation of CHM inversion due to the non-volume decorrelation. Different baselines produced different threshold heights, making CHM inversion only accurate for a limited range of forest height around the threshold. The optimal baseline produced a CHM with R2 of 0.605 and RMSE of 2.67 m. Additionally, we found that using multiple baselines has the potential to improve CHM inversion, improving the R2 to 0.827 and RMSE to 0.876 m in our study.
Auteurs, date et publication :
Auteurs Zhanmang Liao , Binbin He , Albert I.J.M. van Dijk , Xiaojing Bai , Xingwen Quan
Publication : Remote Sensing of Environment
Date : 2018
Volume : 210
Pages : 403–421
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs J. Aaron Hogan , Bruno Hérault , Bénédicte Bachelot , Anaїs Gorel , Marianne Jounieaux , Christopher Baraloto
Publication : Ecological Applications
Date : 2018
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Abstract Determining the species compositions of local assemblages is a prerequisite to understanding how anthropogenic disturbances affect biodiversity. However, biodiversity measurements often remain incomplete due to the limited efficiency of sampling methods. This is particularly true in freshwater tropical environments that host rich fish assemblages, for which assessments are uncertain and often rely on destructive methods. Developing an efficient and nondestructive method to assess biodiversity in tropical freshwaters is highly important. In this study, we tested the efficiency of environmental DNA (eDNA) metabarcoding to assess the fish diversity of 39 Guianese sites. We compared the diversity and composition of assemblages obtained using traditional and metabarcoding methods. More than 7,000 individual fish belonging to 203 Guianese fish species were collected by traditional sampling methods, and $sim$17 million reads were produced by metabarcoding, among which $sim$8 million reads were assigned to 148 fish taxonomic units, including 132 fish species. The two methods detected a similar number of species at each site, but the species identities partially matched. The assemblage compositions from the different drainage basins were better discriminated using metabarcoding, revealing that while traditional methods provide a more complete but spatially limited inventory of fish assemblages, metabarcoding provides a more partial but spatially extensive inventory. eDNA metabarcoding can therefore be used for rapid and large-scale biodiversity assessments, while at a local scale, the two approaches are complementary and enable an understanding of realistic fish biodiversity.
Auteurs, date et publication :
Auteurs Kévin Cilleros , Alice Valentini , Luc Allard , Tony Dejean , Roselyne Etienne , Gaël Grenouillet , Amaia Iribar , Pierre Taberlet , Régis Vigouroux , Sébastien Brosse
Publication : Molecular Ecology Resources
Date : 2019
Volume : 19
Issue : 1
Pages : 27–46
Catégorie(s)
#CIRAD #CNRS #eDNA #FORET ParacouRésumé
Tropical forests harbor the greatest terrestrial biodiversity and provide various ecosystem services. The increase of human activities on these forests, among which logging, makes the conservation of biodiversity and associated services strongly dependent on the sustainability of these activities. However the indicators commonly used to assess the impact of forest exploitation, namely species richness and biomass, provide a limited understanding of their sustainability. Here, we assessed the sustainability of common forest exploitation in the Guiana Shield studying the recovery of two ecosystem services i.e. carbon storage and wood stock, and an ecosystem function i.e. seed dispersal by animals. Specifically, we compared total and commercial biomass, as well as functional composition in seed size of animal-dispersed species in replicated forest plots before and 27 years after exploitation. Species richness is also studied to allow comparison. While species richness was not affected by forest exploitation, total and commercial biomass as well as seed size of animal-dispersed species decreased 27 years after exploitation, similarly to forests affected by hunting. These results show that ecosystem services and function likely did not recover even at the lowest intensity of forest exploitation studied, questioning the sustainability of the most common rotation-cycle duration applied in the tropics.
Auteurs, date et publication :
Auteurs Benjamin Yguel , Camille Piponiot , Ariane Mirabel , Aurelie Dourdain , Bruno Hérault , Sylvie Gourlet-Fleury , Pierre-Michel Forget , Colin Fontaine
Publication : Forest Ecology and Management
Date : 2019
Volume : 433
Pages : 528-534