Auteurs, date et publication :
Auteurs Benjamin Brede , Louise Terryn , Nicolas Barbier , Harm M Bartholomeus , Renée Bartolo , Kim Calders , Géraldine Derroire , Sruthi Krishna Moorthy , Alvaro Lau , Shaun R Levick , Pasi Raumonen , Hans Verbeeck , Di Wang , Tim Whiteside , Jens Van Der Zee , Martin Herold
Publication : Remote Sensing of Environment
Date : 2025
Volume : 280
Issue : July
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Mixing N-fixing trees with eucalypts is an attractive option to improve the long-term soil N status in fast-growing plantations established in tropical soils. A randomized block design was replicated at four sites in Brazil to compare the biogeochemical cycles in mono-specific stands of Eucalyptus (100E) and Acacia mangium (100A) with mixed species plantations in a proportion of 1:1 (50A50E). Our study aimed to assess the effects of introducing A. rnangium trees in Eucalyptus plantations on atmospheric N-2 fixation, N cycling and soil organic matter stocks. Litterfall and soil N mineralization were measured over the last two years of the rotation (4-6 years after planting). Aboveground N accumulation in the trees and C and N stocks in the forest floor and in the top soil were intensively sampled at harvesting age. N-2 fixation rates were estimated using the natural abundance of N-15 as well as by the difference between total N stocks in 100A and 50A50E relative to 100E (accretion method). While the N-15 natural abundance method was unsuitable, the accretion method showed consistently across the four sites that atmospheric N fixation reached about 250 and 400 kg N ha(-1) rotation(-1) in 50A50E and 100A, respectively. Except at one site with high mortality, N contents within trees at harvesting were approximately 40% higher in 100A than in 100E. Mean N contents in litterfall and N mineralization rates were about 60% higher in 100A than in 100E, with intermediate values in 50A50E. The amounts of N in litterfall were much more dependent on soil N mineralization rates for acacia trees than for eucalypt trees. Soil C and N stocks were dependent on soil texture but not influenced by tree species. N budgets over a 6-year rotation were enhanced by about 65 kg N ha(-1) yr(-1) in 100A and 40 kg N ha(-1) yr(-1) in 50A50E relative to monospecific eucalypt plantations. Introducing N-fixing trees in eucalypt plantations might therefore contribute to reducing the need for mineral N fertilization in the long-term.
Auteurs, date et publication :
Auteurs M. Voigtlaender , C. B. Brandani , D. R. M. Caldeira , F. Tardy , J. -P. Bouillet , J. L. M. Goncalves , M. Z. Moreira , F. P. Leite , D. Brunet , R. R. Paula , J. -P. Laclau
Publication : FOREST ECOLOGY AND MANAGEMENT
Date : 2019
Volume : 436
Pages : 56-67
Catégorie(s)
#ANR-Citation #CIRAD #FORET ItatingaRésumé
Challenging evaluation of tropical forest biodiversity requires the reporting of taxonomic diversity but also the systematic characterization of wood properties in order to discover new promising species for timber industry. Among wood properties, the dimensional stability is regarded as a major technological characteristic to validate whether a wood species is adapted to commercial uses. Cell structure and organization are known to influence the drying shrinkage making wood density and microfibrils angle markers of choice to predict wood dimensional stability. On the contrary the role of wood extractive content remains unclear. This work focuses on the fast-growing tropical species Bagassa guianensis and we report herein a correlation between heartwood drying shrinkage and extractive content. Chemical extractions and shrinkage experiments were performed on separate wood twin samples to better evaluate correctly how secondary metabolites influence the wood shrinkage behaviour. Extractive content were qualitatively and quantitatively analysed using HPLC and NMR spectroscopy. We found that B guianensis heartwood has a homogeneous low shrinkage along its radius that could not be explained only by its basic density. In fact the low drying shrinkage is correlated to the high extractive content and a corrected model to improve the prediction of wood dimensional stability is presented. Additionally NMR experiments conducted on sapwood and heartwood extracts demonstrate that secondary metabolites biosynthesis occurs in sapwood thus revealing B. guianensis as a Juglans-Type heartwood formation. This work demonstrates that B. guianensis, a fast-growing species associated with high durability and high dimensional stability, is a good candidate for lumber production and commercial purposes.
Auteurs, date et publication :
Auteurs Julie Bossu , Jacques Beauchêne , Yannick Estevez , Christophe Duplais , Bruno Clair , Warren Batchelor
Publication : Plos One
Date : 2016
Volume : 11
Issue : 3
Pages : e0150777
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Knowledge of the wood properties of tropical tree species is still relatively limited, making that timber exploitation focuses on a few abundant, large-diameter species. Very few is known about small diameter trees although they may be used, directly as round wood, in construction timber building. The aim of this work was to determine the wood natural durability of 8 candidate species for roundwood building in French Guiana ; Oxandra askeckii, Goupia glabra, Lecythis persistens, Hymenopus heteromorphus, Pouteria bangii, Licania alba, Tachigali melinonii, Simarouba amara and Virola surinamensis wood samples were exposed to white rots (European and tropical), brown rot (European) and European subterranean termites (using non-choice and multi-choice tests), in laboratory conditions by screening tests adapted from European standards.
Auteurs, date et publication :
Auteurs Maëva Leroy , Kévin Candelier , Jérémie Damay , Julie Bossu , Romain Lehnebach , Marie-France Thevenon , Jacques Beauchene , Bruno Clair
Date : 1970
Catégorie(s)
#⛔ No DOI found #CIRAD #FORET ParacouRésumé
Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5–7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions.
Auteurs, date et publication :
Auteurs Camille S. Delavaux , Thomas W. Crowther , Constantin M. Zohner , Niamh M. Robmann , Thomas Lauber , Johan van den Hoogen , Sara Kuebbing , Jingjing Liang , Sergio De-Miguel , Gert Jan Nabuurs , Peter B. Reich , Meinrad Abegg , Yves C. Adou Yao , Giorgio Alberti , Angelica M. Almeyda Zambrano , Braulio Vilchez Alvarado , Esteban Alvarez-Dávila , Patricia Alvarez-Loayza , Luciana F. Alves , Christian Ammer
Publication : Nature
Date : 2025
Volume : 621
Issue : November 2022
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Leaf area is a key structural characteristic of forest canopies because of the role of leaves in controlling many biological and physical processes occurring at the biosphere-atmosphere transition. High pulse density Airborne Laser Scanning (ALS) holds promise to provide spatially resolved and accurate estimates of plant area density (PAD) in forested landscapes, a key step in understanding forest functioning: phenology, carbon uptake, transpiration, radiative balance etc. Inconsistencies between different ALS sensors is a barrier to generating globally harmonised PAD estimates. The basic assumption on which PAD estimation is based is that light attenuation is proportional to vegetation area density. This study shows that the recorded extinction strongly depends on target detectability which is influenced by laser characteristics (power, sensitivity, wavelength). Three different airborne laser scanners were flown over a wet tropical forest at the Paracou research station in French Guiana. Different sensors, flight heights and transmitted power levels were compared. Light attenuation was retrieved with an open source ray-tracing code (http://amapvox.org). Direct comparison revealed marked differences (up-to 25% difference in profile-averaged light attenuation rate and 50% difference at particular heights) that could only be explained by differences in scanner characteristics. We show how bias which may occur under various acquisition conditions can generally be mitigated by a sensor intercalibration. Alignment of light weight lidar attenuation profiles to ALS reference attenuation profiles is not always satisfactory and we discuss what are the likely sources of discrepancies. Neglecting the dependency of apparent light attenuation on scanner properties may lead to biases in estimated vegetation density commensurate to those affecting light attenuation estimates. Applying intercalibration procedures supports estimation of plant area density independent of acquisition characteristics.
Auteurs, date et publication :
Auteurs Grégoire Vincent , Philippe Verley , Benjamin Brede , Guillaume Delaitre , Eliott Maurent , James Ball , Ilona Clocher , Nicolas Barbier
Publication : Remote Sensing of Environment
Date : 2023
Volume : 286
Issue : December 2022
Pages : 113442
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The purpose of this paper is twofold, considering first the generalization of a multichannel speckle filter in order to handle temporal stacks of polarimetric SLC SAR data, and secondly the development of an ad hoc performance indicator based on the Polarimetric Orientation Angle (POA) in order to better estimate the resulting speckle reduction than the standard Equivalent Number of Looks (ENL) over densely vegetated regions, like tropical forests. Being based on the ability of PolSAR measurements to retrieve ground slopes through dense vegetation, this performance indicator requires the use of low frequencies such as P-band, as well as fully polarimetric data. This study has thereby a particular interest in the context of the upcoming BIOMASS spaceborne mission whose launch is scheduled in 2023, and makes use of data from the TropiSAR airborne campaign initiated in the early stage of the mission developments. Conducted over several test sites of tropical dense forests in French Guiana, this campaign gives us the opportunity herein to exploit P-band temporal stacks with repeated time intervals transposable to BIOMASS in terms of signal decorrelation. The application of the generalized multichannel speckle filter to the Paracou test site dataset reveals the limitations of the standard ENL analytical formula to assess speckle reduction in the case of spatially correlated media like dense forests, and for this purpose the interest of the correlation between POA and azimuthal slopes computed from an independent Digital Surface Model.
Auteurs, date et publication :
Auteurs Colette Gelas , Ludovic Villard , Laurent Ferro-Famil , Laurent Polidori , Thierry Koleck , Sandrine Daniel
Publication : Remote Sensing
Date : 2021
Volume : 13
Issue : 1
Pages : 142
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The three-dimensional (3-D) structure of forests, especially the vertical structure, is an important parameter of forest ecosystem modeling for monitoring ecological change. Synthetic aperture radar tomography (TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. Due to the advantages of super-resolution imaging and a small number of measurements, distribution compressive sensing (DCS) inversion techniques for polarimetric SAR tomography were successfully developed and applied. This paper addresses the 3-D imaging of forested areas based on the framework of DCS using fully polarimetric (FP) multibaseline SAR interferometric (MB-InSAR) tomography at the P-band. A new DCS-based FP TomoSAR method is proposed: a new wavelet-based distributed compressive sensing FP TomoSAR method (FP-WDCS TomoSAR method). The method takes advantage of the joint sparsity between polarimetric channel signals in the wavelet domain to jointly inverse the reflectivity profiles in each channel. The method not only allows high accuracy and super-resolution imaging with a low number of acquisitions, but can also obtain the polarization information of the vertical structure of forested areas. The effectiveness of the techniques for polarimetric SAR tomography is demonstrated using FP P-band airborne datasets acquired by the ONERA SETHI airborne system over a test site in Paracou, French Guiana.
Auteurs, date et publication :
Auteurs Lei Liang , Xinwu Li , Xizhang Gao , Huadong Guo
Publication : Journal of Applied Remote Sensing
Date : 2015
Volume : 9
Issue : 1
Pages : 095048
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Salicaceae have been enlarged to include a majority of the species formerly placed in the polyphyletic tropical Flacourtiaceae. Several studies have reported a peculiar and infrequently formed multilayered structure of tension wood in four of the tropical genera. Tension wood is a tissue produced by trees to restore their vertical orientation and most studies have focused on trees developing tension wood by means of cellulose-rich, gelatinous fibres, as in Populus and Salix (Salicaceae s.s.). This study aims to determine if the multilayered structure of tension wood is an anatomical characteristic common in other Salicaceae and, if so, how its distribution correlates to phylogenetic relationships. Therefore, we studied the tension wood of 14 genera of Salicaceae and two genera of Achariaceae, one genus of Goupiaceae and one genus of Lacistemataceae, families closely related to Salicaceae or formerly placed in Flacourtiaceae. Opposite wood and tension wood were compared with light microscopy and three-dimensional laser scanning confocal microscopy. The results indicate that a multilayered structure of tension wood is common in the family except in Salix, Populus and one of their closest relatives, Idesia polycarpa. We suggest that tension wood may be a useful anatomical character in understanding phylogenetic relationships in Salicaceae. Further investigation is still needed on the tension wood of several other putatively close relatives of Salix and Populus, in particular Bennettiodendron, Macrohasseltia and Itoa.
Auteurs, date et publication :
Auteurs Barbara Ghislain , Eric-André Nicolini , Raïssa Romain , Julien Ruelle , Arata Yoshinaga , Mac H. Alford , Bruno Clair
Publication : Botanical Journal of the Linnean Society
Date : 2016
Volume : 182
Issue : 4
Pages : 744–756
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Our study aims to provide a comparison of the P- and L-band TomoSAR profiles, Land Vegetation and Ice Sensor (LVIS), and discrete return LiDAR to assess the ability for TomoSAR to monitor and estimate the tropical forest structure parameters for enhanced forest management and to support biomass missions. The comparison relies on the unique UAVSAR Jet propulsion Laboratory (JPL)/NASA L-band data, P-band data acquired by ONERA airborne system (SETHI), Small Footprint LiDAR (SFL), and NASA Land, Vegetation and Ice Sensor (LVIS) LiDAR datasets acquired in 2015 and 2016 in the frame of the AfriSAR campaign. Prior to multi-baseline data processing, a phase residual correction methodology based on phase calibration via phase center double localization has been implemented to improve the phase measurements and compensate for the phase perturbations, and disturbances originated from uncertainties in allocating flight trajectories. First, the vertical structure was estimated from L- and P-band corrected Tomography SAR data measurements, then compared with the canopy height model from SFL data. After that, the SAR and LiDAR three-dimensional (3D) datasets are compared and discussed at a qualitative basis at the region of interest. The L- and P-band’s performance for canopy penetration was assessed to determine the underlying ground locations. Additionally, the 3D records for each configuration were compared with their ability to derive forest vertical structure. Finally, the vertical structure extracted from the 3D radar reflectivity from L- and P-band are compared with SFL data, resulting in a root mean square error of 3.02 m and 3.68 m, where the coefficient of determination shows a value of 0.95 and 0.93 for P- and L-band, respectively. The results demonstrate that TomoSAR holds promise for a scientific basis in forest management activities.
Auteurs, date et publication :
Auteurs Ibrahim El Moussawi , Dinh Ho Tong Minh , Nicolas Baghdadi , Chadi Abdallah , Jalal Jomaah , Olivier Strauss , Marco Lavalle , Yen-Nhi Ngo
Publication : Remote Sensing
Date : 2019
Volume : 11
Issue : 16
Pages : 1934