Résumé
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
Catégorie(s)
#CIRAD #FORET ParacouRésumé
A Amazônia é a maior floresta tropical do mundo e pelo menos 147 espécies de morcegos ocorrem neste ambiente. A despeito desta grande riqueza, a diversidade de morcegos da Amazônia é pobremente conhecida e existem grandes lacunas neste conhecimento. O objetivo do presente trabalho foi descrever a assembleia de morcegos ocorrentes na região do Médio Teles Pires (MTP), no sul da Amazônia. Além disso, avaliou-se a similaridade dessa assembleia em relação a 14 assembleias estudadas em outras localidades amazônicas e avaliou-se a correlação entre as similaridades destas localidades e suas distâncias. Trinta e três espécies de morcegos foram registradas, representando 71% das espécies estimadas (Jackknife2). As três espécies com maior abundância relativa foram: Carollia perspicillata, Pteronotus parnellii e Phyllostomus hastatus que somadas contam com mais de 50% das capturas. O grupo funcional dos frugívoros obteve o maior número de espécies capturadas. Foi encontrada uma correlação negativa entre as distâncias e as similaridades das assembleias de morcegos amazônicos (r = -0,22; p = 0,014). A distância geográfica pode explicar apenas 6% da similaridade entre as assembleias analisadas, ainda assim, as similaridades destas assembleias permitem que as mesmas sejam agrupadas por suas distâncias geográficas. Além disso, a fauna de morcegos do MTP é diferenciada de outras áreas da Amazônia o que lhe confere um papel especial na conservação dos morcegos amazônicostextless/ptextgreater
Auteurs, date et publication :
Auteurs João M. D. Miranda , Luciana Zago , Fernando Carvalho , Marcelo B. G. Rubio , Itiberê P. Bernardi , João M. D. MIRANDA , Luciana ZAGO , Fernando CARVALHO , Marcelo B. G. RUBIO , Itiberê P. BERNARDI
Publication : Acta Amazonica
Date : 2015
Volume : 45
Issue : 1
Pages : 89–100
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs D. Audigeos , L. Brousseau , S. Traissac , C. Scotti-Saintagne , I. Scotti
Publication : Journal of Evolutionary Biology
Date : 2013
Volume : 26
Issue : 3
Pages : 529–544
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Modeling soil water availability for tropical trees is a prerequisite to predicting the future impact of climate change on tropical forests. In this paper we develop a discrete-time deterministic water balance model adapted to tropical rainforest climates, and we validate it on a large dataset that includes micro-meteorological and soil parameters along a topographic gradient in a lowland forest of French Guiana. The model computes daily water fluxes (rainfall interception, drainage, tree transpiration and soil plus understorey evapotranspiration) and soil water content using three input variables: daily precipitation, potential evapotranspiration and solar radiation. A novel statistical approach is employed that uses Time Domain Reflectometer (TDR) soil moisture data to estimate water content at permanent wilting point and at field capacity, and root distribution. Inaccuracy of the TDR probes and other sources of uncertainty are taken into account by model calibration through a Bayesian framework. Model daily output includes relative extractable water, REW, i.e. the daily available water standardized by potential available water. The model succeeds in capturing temporal variations in REW regardless of topographic context. The low Root Mean Square Error of Predictions suggests that the model captures the most important drivers of soil water dynamics, i.e. water refilling and root water extraction. Our model thus provides a useful tool to explore the response of tropical forests to climate scenarios of changing rainfall regime and intensity. © 2011 Elsevier B.V.
Auteurs, date et publication :
Auteurs Fabien Wagner , Bruno Hérault , Clément Stahl , Damien Bonal , Vivien Rossi
Publication : Agricultural and Forest Meteorology
Date : 2011
Volume : 151
Issue : 9
Pages : 1202–1213
Catégorie(s)
#CIRAD #FORET ParacouRésumé
There is mounting empirical evidence that lianas affect the carbon cycle of tropical forests. However, no single vegetation model takes into account this growth form, although such efforts could greatly improve the predictions of carbon dynamics in tropical forests. In this study, we incorporated a novel mechanistic representation of lianas in a dynamic global vegetation model (the Ecosystem Demography Model). We developed a liana-specific plant functional type and mechanisms representing liana–tree interactions (such as light competition, liana-specific allometries, and attachment to host trees) and parameterized them according to a comprehensive literature meta-analysis. We tested the model for an old-growth forest (Paracou, French Guiana) and a secondary forest (Gigante Peninsula, Panama). The resulting model simulations captured many features of the two forests characterized by different levels of liana infestation as revealed by a systematic comparison of the model outputs with empirical data, including local census data from forest inventories, eddy flux tower data, and terrestrial laser scanner-derived forest vertical structure. The inclusion of lianas in the simulations reduced the secondary forest net productivity by up to 0.46 tC ha−1 year−1, which corresponds to a limited relative reduction of 2.6% in comparison with a reference simulation without lianas. However, this resulted in significantly reduced accumulated above-ground biomass after 70 years of regrowth by up to 20 tC/ha (19% of the reference simulation). Ultimately, the simulated negative impact of lianas on the total biomass was almost completely cancelled out when the forest reached an old-growth successional stage. Our findings suggest that lianas negatively influence the forest potential carbon sink strength, especially for young, disturbed, liana-rich sites. In light of the critical role that lianas play in the profound changes currently experienced by tropical forests, this new model provides a robust numerical tool to forecast the impact of lianas on tropical forest carbon sinks.
Auteurs, date et publication :
Auteurs Manfredo di Porcia e Brugnera , Félicien Meunier , Marcos Longo , Sruthi M. Krishna Moorthy , Hannes De Deurwaerder , Stefan A. Schnitzer , Damien Bonal , Boris Faybishenko , Hans Verbeeck
Publication : Global Change Biology
Date : 2025
Volume : 25
Issue : 11
Pages : 3767-3780
Catégorie(s)
#ANR-Citation #CIRAD #FORET ParacouRésumé
The preparation of tropical wood surface sections for time‐of‐flight secondary ion mass spectrometry imaging is described, and the use of delayed extraction of secondary ions and its interest for the analysis of vegetal surface are shown. The method has been applied to the study by time‐of‐flight secondary ion mass spectrometry imaging with a resolution of less than one micron of a tropical wood species, Dicorynia guianensis, which is one of the most exploited wood in French Guiana for its durable heartwood. The heartwood of this species exhibits an economical importance, but its production is not controlled in forestry. Results show an increase of tryptamine from the transition zone and a concomitant decrease of inorganic ions and starch fragment ions. These experiments lead to a better understanding of the heartwood formation and the origin of the natural durability of D. guianensis.
Auteurs, date et publication :
Auteurs Quentin P. Vanbellingen , Tingting Fu , Claudia Bich , Nadine Amusant , Didier Stien , Serge Della-Negra , David Touboul , Alain Brunelle
Publication : Journal of Mass Spectrometry
Date : 2016
Volume : 51
Issue : 6
Pages : 412–423
Catégorie(s)
#CIRAD #FORET ParacouRésumé
To grow straight, plants need a motor system that controls posture by generating forces to offset gravity. This motor function in trees was long thought to be only controlled by internal forces induced in wood. Here we provide evidence that bark is involved in the generation of mechanical stresses in several tree species. Saplings of nine tropical species were grown tilted and staked in a shadehouse and the change in curvature of the stem was measured after releasing from the pole and after removing the bark. This first experiment evidenced the contribution of bark in the up-righting movement of tree stems. Combined mechanical measurements of released strains on adult trees and microstructural observations in both transverse and longitudinal/tangential plane enabled us to identify the mechanism responsible for the development of asymmetric mechanical stress in the bark of stems of these species. This mechanism does not result from cell wall maturation like in wood, or from the direct action of turgor pressure like in unlignified organs, but is the consequence of the interaction between wood radial pressure and a smartly organized trellis structure in the inner bark.
Auteurs, date et publication :
Auteurs Bruno Clair , Barbara Ghislain , Jonathan Prunier , Romain Lehnebach , Jacques Beauchêne , Tancrède Alméras
Publication : New Phytologist
Date : 2025
Volume : 221
Issue : 1
Pages : 209-217
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Recent studies have shown that the inner bark is implicated in the postural control of inclined tree stems through the interaction between wood radial growth and tangential expansion of a trellis f...
Auteurs, date et publication :
Auteurs Romain Lehnebach , Léopold Doumerc , Bruno Clair , Tancrède Alméras
Publication : Botany
Date : 2019