Résumé

The potential of interferometric synthetic aperture radar (InSAR) heights from TanDEM-X for vegetation canopy height and aboveground biomass (AGB) estimation has long been recognized. Penetration of X-band into the canopy affects these estimations. Thus, the canopy height and AGB retrieval from InSAR are typically biased and cannot be compared directly to estimates from other data sources. The objective of this letter was to apply a penetration depth model to compensate for height biases in TanDEM-X InSAR heights. The resulting canopy height estimates are subsequently converted to AGB estimates using regression models. The uncorrected InSAR heights of the forest canopy are biased due to the penetration of the signal into the canopy and differ substantially to light detection and ranging (LiDAR) canopy height estimates. The application of the penetration depth compensation results in unbiased forest canopy height estimates and AGB regression models that are comparable between InSAR and LiDAR. These results indicate that TanDEM-X InSAR and LiDAR technologies can be used to estimate AGB in complex tropical forests suggesting a synergistic use of these fundamentally different observation concepts.

Auteurs, date et publication :

Auteurs M. Schlund , S. Erasmi , K. Scipal

Publication : IEEE Geoscience and Remote Sensing Letters

Date : 2020

Volume : 17

Issue : 3

Pages : 367-371

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs Isabelle Pierrejean , Theophile Mehinto , Jacques Beauchene

Publication : Pro Ligno

Date : 2025

Volume : 13

Issue : 1

Pages : 3–17

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs A. Hamadi , L. Villard , P. Borderies , C. Albinet , T. Koleck , T. Le Toan

Publication : IEEE Geoscience and Remote Sensing Letters

Date : 2017

Volume : 14

Issue : 11

Pages : 1918–1922

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

The article “Conceptualization, modeling and environmental impact assessment of a natural rubber techno-ecological system with nutrient, water and energy integration” by Martinez-Hernandez E and Hernandez JE (2018, 185: 707–722) is based on a compilation of published information processed through a model linking natural rubber making to latex yield in rubber tree fields. Its main conclusion is that recycling processing wastewater could increase the yield by 62%. However, the statement that nitrogen input can significantly increase latex yield is based on a wrong quotation of the only cited reference. Moreover, the outputs of the model were not validated by actual data. The published literature actually shows that possible increase of latex yield by fertilization or irrigation would be much lower than 62%, and this invalidates the model. Its conclusions can then not be considered scientifically established.

Auteurs, date et publication :

Auteurs Philippe Thaler

Publication : Journal of Cleaner Production

Date : 2019

Volume : 210

Pages : 1063-1064

Catégorie(s)

#CIRAD #FORET Rubberflux

Résumé

The objective of this study is to assess and compare different above-ground biomass (AGB) estimation models for tropical forest using P-band SAR tomography. In this paper, we investigate (1) comparative performance of back-projection and Capon beamforming tomographic estimators to analyze the vertical structure of tropical forest 2) impact of terrain slope correction on tomogram reflectivity and AGB estimates 3) correlation of tomogram reflectivity at 30m to forest AGB using different models 4) possibility of using tomographic retrieved height to improve the AGB estimation. The performance of these models is evaluated using dataset acquired during TropiSAR 2009 by ONERA over the Paracou site.

Auteurs, date et publication :

Auteurs N. Ramachandran , S. Tebaldini , M. M. d'Alessandro , S. Saatchi , O. Dikshit

Date : 2019

Pages : 1-5

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Two-level data sets consist of higher level (say population) traits computed from lower level (say individual) observations. Cluster analysis for two-level data sets aims at classifying populations using individual observations. Most existing techniques to classify populations in two-level data sets actually operate on population traits (e.g. the k-means algorithm), thus disregarding the within-population individual variability. In this study, the k-means algorithm was compared with a recently developed classification method that accounts for within-population variability. Populations were tree species in a tropical rain forest in French Guiana, and individual observations were tree diameters and diameter growth rates. Tree species were classified according to either their diameter and growth rate, or to their asymptotic diameter distribution as predicted by an Usher matrix population model. In both cases, the k-means algorithm and the two-level classification method defined species clusters that were significantly related according to the Rand index. Nevertheless, clusters showed increasing differences between the two methods as the within-population individual variability increased. Whereas the k-means algorithm produced equally-sized spherical clusters, the two-level classification method adapted the size and shape of clusters to the individual within-population variability. Taking account of individual variability to classify populations in ecology may thus be important, albeit rarely done.

Auteurs, date et publication :

Auteurs Nicolas Picard , Avner Bar-Hen

Publication : Ecological Informatics

Date : 2013

Volume : 15

Pages : 1–7

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Selection for drought-tolerant clones has become a major challenge in rubber breeding programs undertaken to ensure the sustainability of natural rubber production, as rubber plantations are expanding in drought-prone areas. Xylem vulnerability to cavitation is a trait related to drought-induced mortality. It can be rapidly evaluated without subjecting plant materials to drought stress, making it useful in large-scale screening for drought tolerance in the near future. We first compared the most widely used techniques for measuring vulnerability to cavitation (air pressurization and Cavitron) on this species, and the effect of sample conditions (size, age and sunlight exposure), in order to ensure reliable analysis. Secondly, ten rubber clones were compared for their xylem vulnerability to cavitation in branches and petioles, and for other traits related to drought response, including stomatal response and leaf shedding occurring during a simulated drought. We also tested the plasticity of vulnerability to cavitation on two clones grown in three locations with contrasting precipitation regimes. We found no clonal variability and a small phenotypic plasticity for xylem vulnerability to cavitation in branches. However, clonal differences in xylem vulnerability to cavitation were found in petioles, and clones also showed differences in stomatal response and in leaf shedding behavior in response to a simulated drought. Our study suggests a genetic canalization for vulnerability to cavitation in organs critical for survival, such as branches, whereas there are clonal differences for traits related to drought avoidance: vulnerability to cavitation of petioles, leaf shedding behavior and stomatal response. The insights gained in this study for screening rubber tree clones for drought tolerance is also discussed.

Auteurs, date et publication :

Auteurs Wanploy Jinagool , Ratchanee Rattanawong , Krissada Sangsing , Têtè Sévérien Barigah , Frederic Gay , Hervé Cochard , Poonpipope Kasemsap , Stéphane Herbette

Publication : The Journal of Plant Hydraulics

Date : 2025

Volume : 2

Pages : 14

Catégorie(s)

#CIRAD #FORET Rubberflux

Résumé

textlessptextgreaterThe 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 textless 2000 mm yrtextlesssuptextgreater−1textless/suptextgreater (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 textless 2000 mm yrtextlesssuptextgreater−1textless/suptextgreater.textless/ptextgreater

Auteurs, date et publication :

Auteurs Fabien H. Wagner , Bruno Hérault , Damien Bonal , Clément Stahl , Liana O. Anderson , Timothy R. Baker , Gabriel Sebastian Becker , Hans Beeckman , Danilo Boanerges Souza , Paulo Cesar Botosso , David M. J. S. Bowman , Achim Bräuning , Benjamin Brede , Foster Irving Brown , Jesus Julio Camarero , Plínio Barbosa Camargo , Fernanda C. G. Cardoso , Fabrício Alvim Carvalho , Wendeson Castro , Rubens Koloski Chagas

Publication : Biogeosciences

Date : 2016

Volume : 13

Issue : 8

Pages : 2537–2562

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Establishing a direct link between climate change and fluctuations in animal populations through long-term monitoring is difficult given the paucity of baseline data. We hypothesized that social wasps are sensitive to climatic variations, and thus studied the impact of ENSO events on social wasp populations in French Guiana. We noted that during the 2000 La Niña year there was a 77.1% decrease in their nest abundance along ca. 5 km of forest edges, and that 70.5% of the species were no longer present. Two simultaneous 13-year surveys (1997–2009) confirmed the decrease in social wasps during La Niña years (2000 and 2006), while an increase occurred during the 2009 El Niño year. A 30-year weather survey showed that these phenomena corresponded to particularly high levels of rainfall, and that temperature, humidity and global solar radiation were correlated with rainfall. Using the Self-Organizing Map algorithm, we show that heavy rainfall during an entire rainy season has a negative impact on social wasps. Strong contrasts in rainfall between the dry season and the short rainy season exacerbate this effect. Social wasp populations never recovered to their pre-2000 levels. This is probably because these conditions occurred over four years; heavy rainfall during the major rainy seasons during four other years also had a detrimental effect. On the contrary, low levels of rainfall during the major rainy season in 2009 spurred an increase in social wasp populations. We conclude that recent climatic changes have likely resulted in fewer social wasp colonies because they have lowered the wasps' resistance to parasitoids and pathogens. These results imply that Neotropical social wasps can be regarded as bio-indicators because they highlight the impact of climatic changes not yet perceptible in plants and other animals.

Auteurs, date et publication :

Auteurs Alain Dejean , Régis Céréghino , James M. Carpenter , Bruno Corbara , Bruno Hérault , Vivien Rossi , Maurice Leponce , Jérome Orivel , Damien Bonal , Nicolas Salamin

Publication : Plos One

Date : 2011

Volume : 6

Issue : 11

Pages : e27004

Catégorie(s)

#CIRAD #FORET Paracou

Auteurs, date et publication :

Auteurs Cecília Lira Melo de Oliveira Santos , Rubens Augusto Camargo Lamparelli , Dantas Araújo Figueiredo , Gleyce Kelly , Stéphane Dupuy , Julie Boury , Ana Cláudia dos Santos Luciano , Ricardo da Silva Torres , Guerric le Maire

Publication : Remote Sensing

Date : 2025

Volume : 11

Issue : 3

Pages : 334

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE