Résumé
Tropical forests play a key role in the global carbon balance and in natural climate change mitigation, as they account for 68% of global forest carbon stocks and represent up to 30% of global soil carbon stocks. However, major uncertainties remain regarding the long-term sustainability of their carbon sink capacity when considering the full greenhouse gas exchange, including methane (CH4) and nitrous oxide (N2O) fluxes, and accurately identifying and quantifying all sources and sinks.In this line, we present here original continuous high-frequency ecosystem (eddy covariance) and soil (automated chamber) CH4 and N2O flux data from a 2.5-year study in a seasonally wet tropical forest at the Guyaflux experimental site, French Guiana. The main objective of our study was to assess the seasonal patterns of CH4 and N2O exchange at the ecosystem and soil levels, and to identify the environmental drivers. Seasonal variations in ecosystem and soil CH4 and N2O fluxes were tremendous, with generally higher CH4 and N2O emissions in the wettest than in the driest season. Global radiation, soil water content and soil temperature were the main drivers of seasonal variation in ecosystem and soil CH4 and N2O fluxes. Furthermore, based on eddy covariance measurements of all greenhouse gases, i.e. CH4, N2O and CO2, the forest was overall a significant carbon sink (-1,875 ± 813 kgC ha-1 y-1, i.e. cumulative net ecosystem exchange), although the ecosystem shifted from a small sink to a small source of CH4 during the wettest season, and remained a more or less small but constant source of N2O. In contrast, soil fluxes in the upper part of the forest within the tower footprint were consistently a CH4 sink, while soil N2O fluxes shifted depending on the season, from a small N2O sink in the driest season to a small source in the wettest season.Our study shows that the carbon sink potential of the Guyaflux forest is not yet compromised by CH4 and N2O emissions. However, under the more frequent extreme conditions of contrasting soil water content and global radiation expected in the future, CH4 and N2O emissions may increase and thus reduce the forest carbon sink.
Auteurs, date et publication :
Auteurs Laëtitia Brechet , Mercedes Ibáñez , Benoît. Burban , Jean-Yves Goret , Clément Stahl , Damien Bonal , Rob Jackson , Ivan Janssens
Date : 2024
Pages : 9235
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Background The availability of soil phosphorus (P) often limits the productivities of wet tropical lowland forests. Little is known, however, about the metabolomic profile of different chemical P compounds with potentially different uses and about the cycling of P and their variability across space under different tree species in highly diverse tropical rainforests.
Results We hypothesised that the different strategies of the competing tree species to retranslocate, mineralise, mobilise, and take up P from the soil would promote distinct soil 31P profiles. We tested this hypothesis by performing a metabolomic analysis of the soils in two rainforests in French Guiana using 31P nuclear magnetic resonance (NMR). We analysed 31P NMR chemical shifts in soil solutions of model P compounds, including inorganic phosphates, orthophosphate mono- and diesters, phosphonates, and organic polyphosphates. The identity of the tree species (growing above the soil samples) explained > 53% of the total variance of the 31P NMR metabolomic profiles of the soils, suggesting species-specific ecological niches and/or species-specific interactions with the soil microbiome and soil trophic web structure and functionality determining the use and production of P compounds. Differences at regional and topographic levels also explained some part of the the total variance of the 31P NMR profiles, although less than the influence of the tree species. Multivariate analyses of soil 31P NMR metabolomics data indicated higher soil concentrations of P biomolecules involved in the active use of P (nucleic acids and molecules involved with energy and anabolism) in soils with lower concentrations of total soil P and higher concentrations of P-storing biomolecules in soils with higher concentrations of total P.
Conclusions The results strongly suggest “niches” of soil P profiles associated with physical gradients, mostly topographic position, and with the specific distribution of species along this gradient, which is associated with species-specific strategies of soil P mineralisation, mobilisation, use, and uptake.
Auteurs, date et publication :
Auteurs Albert Gargallo-Garriga , Jordi Sardans , Joan Llusià , Guille Peguero , Marta Ayala-Roque , Elodie A. Courtois , Clément Stahl , Otmar Urban , Karel Klem , Pau Nolis , Miriam Pérez-Trujillo , Teodor Parella , Andreas Richter , Ivan A. Janssens , Josep Peñuelas
Publication : BMC Plant Biology
Date : 2024
Volume : 24
Issue : 1
Pages : 278
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
We investigated the utility of nuclear and cytoplasmic single nucleotide polymorphism (SNP) markers for timber tracking of the intensively logged and commercialized Amazonian tree Jacaranda copaia. Eight hundred and thirty-two trees were sampled (cambium or leaves) from 38 sampling sites in Bolivia, Brazil, French Guiana, and Peru. A total of 128 SNP markers (113 nuclear, 11 chloroplastic, and 4 mitochondrial) were used for genotyping the samples. Bayesian cluster analyses were carried out to group individuals into homogeneous genetic groups for tests to self-assign groups of individuals or individuals to their population of origin. Cluster analysis based on all the SNP markers detected seven main genetic groups. Genetic differentiation was high among populations (0.484) and among genetic groups (0.415), and populations showed a strong isolation-by-distance pattern. Self-assignment testing of the groups of individuals for all loci was able to determine the population origin of all the samples (accuracy = 100%). Self-assignment tests of individuals were able to assign the origin of 94.5%–100% of individuals (accuracy: 91.7%–100%). Our results show that the use of the 128 SNP markers is suitable to correctly determine the origin of J. copaia timber, and they should be considered a useful tool for customs and local and international police.
Auteurs, date et publication :
Auteurs Lorena Frigini Moro Capo , Bernd Degen , Celine Blanc-Jolivet , Niklas Tysklind , Stephen Cavers , Malte Mader , Barbara Rocha Venancio Meyer-Sand , Kathelyn Paredes-Villanueva , Eurídice Nora Honorio Conorado , Carmen Rosa García-Dávila , Valérie Troispoux , Adline Delcamp , Alexandre Magno Sebbenn
Publication : Forests
Date : 2024
Volume : 15
Issue : 8
Pages : 1478
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Mammal faunas from northern French Guiana (in northeastern Amazonia) and the YavaríUcayali interfluve (in southwestern Amazonia) are the first Amazonian mammal faunas to be comprehensively described in terms of taxonomic composition and community structure. Bats are the most speciose group in each fauna, followed in order of decreasing species richness by rodents, didelphimorphians, carnivorans, xenarthrans or primates, and ungulates. A total of 180 species are known from northern French Guiana and 199 species from the Yavarí-Ucayali interfluve, but an additional 25 species are possibly missing (“pseudoabsent”) from the YavaríUcayali interfluvial inventory; therefore, the increment by which species richness in northeastern Peru exceeds that of northern French Guiana is on the order of 10–25%. Complementarity (dissimilarity) between these faunas is high (79%–89%) for opossums, primates, and rodents, but complementarity is substantially lower for other groups (especially bats, carnivorans, and ungulates), suggesting taxonomic differences in geographic filtering. Most species in both faunas are nocturnal, as might be expected from the abundance of bats, but even among nonflying mammals nocturnal species outnumber diurnal species by about 2:1. Approximately equal numbers of nonflying species in both faunas are arboreal or terrestrial, whereas much smaller numbers are scansorial or semiaquatic; with one possible exception, none is fossorial. Despite such behavioral similarities, these faunas differ in trophic composition and guild membership: substantially more primary consumers are present in the Yavarí-Ucayali interfluve than in northern French Guiana, whereas numbers of secondary consumers and omnivores are similar. Higher primary productivity in western Amazonia, a geomorphologically dynamic landscape with fertile soils and phenologically diverse habitats, could explain faunal differences in both species richness and trophic structure.
Auteurs, date et publication :
Auteurs Robert S. Voss
Publication : American Museum Novitates
Date : 2024
Volume : 2024
Issue : 4019
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Spirotropis longifolia (DC.) Baill. is organized in monodominant forest patches in French Guiana. S. longifolia root nodules and forest soil samples were collected in three monodominant populations of S. longifolia and in four zones, from the S. longifolia core dominance to the adjacent mixed forest where this species was absent. S. longifolia roots presented arbuscular mycorrhizal fungus (AMF) structures, but no ectomycorrhizae. The presence of myconodule-like structures was only noted once. Isolates of S. longifolia and of diverse French Guianese legume trees were 95% identified as Bradyrhizobium spp. and rarely as Rhizobium spp. On a partial 16S rDNA phylogenetic tree, S. longifolia-associated bradyrhizobia were positioned in a separate cluster including the Bradyrhizobium sp. Tv2a-2 strain isolated from Tachigali versicolor in Panama. Bradyrhizobia of other forest legume trees were positioned identically, or differently, in various clusters. A partial 16S-23S rDNA internal transcribed spacer (ITS) phylogenetic tree confirmed that the main cluster accounting for 82% of the direct or trapped bradyrhizobia associated with S. longifolia was situated outside the B. japonicum and B. elkanii superclades, in the Tv2a-2 superclade/Kakadu supergroup. In this cluster, other bradyrhizobia appeared that were associated with legumes from the tribes Ormosieae, Brongniartieae and Dalbergieae, suggesting the possibility of a shared pool of the most ancestral symbionts that are bradyrhizobia with the Caesalpinoid legumes and the early-branching Papilionoid legumes. Curiously, the seven monodominant Fabaceae of the Amazonian forests were exclusively part of these subfamilies. The link between ancestral symbiosis and monodominance still remains to be studied.
Auteurs, date et publication :
Auteurs Christine Le Roux , Emile Fonty , Laurent Brottier , Mathilde Bernard , Yves Prin , Daniel Sabatier
Publication : Symbiosis
Date : 2024
Volume : 94
Issue : 1
Pages : 1-17
Catégorie(s)
#CIRAD #FORET ParacouRésumé
In this paper, we assess the regrowth capacity of tropical forest plots by developing an original computational procedure based on statistical model checking methods. We calibrate a new mathematical model of forest dynamics with respect to post-logging data, produced in the Amazon basin. Our mathematical model is determined by a mechanistic system of ordinary differential equations and integrates a new nonlinear aging term, which is necessary to reproduce the complex post-logging dynamics of the tropical forest plots. Our method is based on an efficient algorithmic procedure that explores the parameter space of the model and computes a score for each parameter value, depending on the distance between the trajectory of the model and the data. We distinguish a group of four reference plots, for which the logging was the most intense, from another group of five non-reference plots, which are fitted a posteriori. Our results provide a set trajectories of the new model, which successfully fit the non-monotone post-logging data on each forest plot, in spite of the high level of biological variability identified in the study site. Rather than a unique set of parameters, we return a small cell of parameters, extracted from the parameter space, which contains in its close vicinity several relevant sets of parameters that are equally able to reproduce the regrowth dynamics of distinct tropical forest plots. The size of the cells that should be extracted from the parameter space increases with the level of biological variability. Finally, we show how to use the calibrated mathematical model for simulating logging scenarios, so as to better understand the temporal dynamics of forest regrowth.
Auteurs, date et publication :
Auteurs Gilles Ardourel , Guillaume Cantin , Benoît Delahaye , Géraldine Derroire , Beatriz M. Funatsu , David Julien
Publication : Ecological Modelling
Date : 2024
Volume : 495
Pages : 110812
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Lapèze J., 2024. – Synthèse des connaissances sur les membracides et les aetalions de Guyane française (Hemiptera : Auchenorrhyncha : Membracidae, Aetalionidae). Partie I : historique et liste des espèces recensées. Faunitaxys, 12(51) : 1 – 35.
https://doi.org/10.57800/faunitaxys-12(51) - https://zoobank.org/192AFF69-9C82-44D7-8E06-80F3E1CAF3D6
Résumé. – Une première liste des membracides et des aetalions de Guyane française est établie. Cette liste est issue d’une compilation des données bibliographiques, de l’analyse de spécimens de collections privées et publiques, ainsi que des données produites par Albino Sakakibara suite à sa collaboration avec la Société entomologique Antilles Guyane. Cette liste recense 302 espèces, 98 genres, 24 tribus et 9 sous-familles de Membracidae et 7 espèces, 4 genres, 2 tribus et 2 sous- familles d’Aetalionidae. Un tableau général renseigne les sources de signalement de chaque taxon, ainsi que les localités type qui se trouvent sur le territoire étudié.
Lapèze J., 2024. – A synthesis of the knowledge of treehoppers from French Guiana (Hemiptera : Membracidae, Aetalionidae) Part I : history and checklist. Faunitaxys, 12(51) : 1 – 35.
Abstract. – A first list of membracids and aetalions of French Guiana is established. This list is the result of a compilation of bibliographic research, analysis of specimens from private and public collections, as well as data produced by Albino Sakakibara following his collaboration with the Société entomologique Antilles-Guyane. This list reports 302 species, 98 genera, 24 tribes and 9 subfamilies of Membracidae and 7 species, 4 genera, 2 tribes and 2 subfamilies of Aetalionidae. McKamey’s (1998) catalog references 67 species of Membracidae for this territory. A detailed history of the work carried out on membracids in French Guiana is presented in a chronological manner. The studied geographical area is briefly presented, while taking in account the numerous confusions which took place around the nomenclatures of the three Guianas. In conclusion, this checklist is only preliminary, because it is obvious that it is far from being complete. Many species remain to be listed, described or recorded. Many taxonomic and systematic changes are still to be made in this family
Auteurs, date et publication :
Auteurs Jérémie Lapèze
Date : 2024
Catégorie(s)
#CIRAD #FORET ParacouRésumé
To improve our understanding of the carbon cycle, precise estimates of forest biomass are needed. High values of dense tropical forest biomass are particularly important, as they determine uncertainties in carbon stock assessment and carbon loss due to deforestation and forest degradation. However, estimating Above Ground Biomass (AGB) of tropical forests based on remote sensing systems remains challenging, most existing satellite systems are not sensitive to AGB in the high range. In this paper, we assess the use of P-band SAR tomography technique to provide AGB with reduced uncertainties in the range of 200-400 Mg.ha -1. We present the expected contribution of the BIOMASS mission in estimating the carbon loss from deforestation and from forest degradation , and in providing the Digital Elevation Model under dense forests.
Auteurs, date et publication :
Auteurs Thuy Le Toan , Ludovic Villard , Dinh Ho Tong Minh , Juan Doblas , Stephane Mermoz , Laurent Ferro-Famil , Thierry Koleck , Alexandre Bouvet , Milena Planells , Laurent Polidori
Publication : The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Date : 2024
Volume : XLVIII-3-2024
Pages : 287-293
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
This paper proposes to quantitatively estimate the potential of 3D SAR imaging for tropical forest characterization using airborne and spaceborne system configuration. A robust forest characterization technique, relying a low-dimensionality model is proposed and is compared with a well-established polarimetric and tomographic approach. The investigated forest descriptors are the underlying ground topography (DTM) and the forest height (CHM). A quantitative performance evaluation reveals that the presented parametric technique achieves high-precision results at both high-resolution (airborne) and low resolution (BIOMASS) modes, whereas existing approaches meet limitations, due the coarse resolution of spaceborne SAR data.
Auteurs, date et publication :
Auteurs Laurent Ferro-Famil , Yue Huang , Pierre-Antoine Bou , Stefano Tebaldini
Publication : The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Date : 2024
Volume : XLVIII-3-2024
Pages : 163-168
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Aboveground Biomass (AGB) estimation performance in a dense tropical forest using Polarimetric Interferometric Synthetic Aperture Radar (PolInSAR) data, at P-and L-band, is evaluated. At high levels of biomass, the backscatter saturation effect leads to a low sensitivity of the backscattered intensity for biomass. This study tries to overcome this problem based on decomposition of PolInSAR data into ground, ground-trunk, and volume components to retrieve the vertical structure information of the forest and polarimetric characteristics of layers. Some sensitive parameters, which extracted from Polarimetric Synthetic Aperture Radar (PolSAR) and PolInSAR data are chosen. Then, many sets of these features are used for assessing biomass estimation using Linear Regression (LR) and Support Vector Machine (SVM) regression models. The data analyzed in this paper are from the P-and L-band airborne dataset acquired by Office National d’Études et de Recherches Aérospatiales (ONERA) over French Guiana in 2009, in the frame of the European Space Agency (ESA) campaign, TropiSAR. The average forest biomass is 374.54 t ha−1 and goes up to 503 t ha−1 for the in-situ plots. The results display that the indicator of double-bounce (CDB) contribution matrix, extracted from PolInSAR data decomposition, is the highest correlated feature to AGB, at both P-and L-band. The combination of PolInSAR indicators improved the Root-Mean-Squared Error (RMSE) values up to 24.76 t ha−1 at P-band and 18.02 t ha−1 at L-band. At the best state, AGB estimation RMSE reduces to 40.95 t ha−1 (12.73%) in simultaneous use of the features derived from PolSAR and PolInSAR data, at P-band. SVM produces a more realistic biomass value than LR. However, cross-validated AGB RMSE of two regression models is close to each other.
Auteurs, date et publication :
Auteurs Sajjad Eini-Zinab , Yasser Maghsoudi , Seyed Ali Sayedain
Publication : International Journal of Remote Sensing
Date : 2020
Volume : 41
Issue : 2
Pages : 433-454