| Records |
| Author |
Aubry-Kientz, Mélaine ; Laybros, Anthony ; Weinstein, Ben ; Ball, James G. C. ; Jackson, Toby ; Coomes, David ; Vincent, Grégoire |
| Title |
Multisensor data fusion for improved segmentation of individual tree crowns in dense tropical forests |
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Journal Article |
| Year |
2021 |
Publication |
IEEE Journal of Selected topics in Applied Earth Observations and Remote Sensing |
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| Volume |
14 |
Issue |
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Pages |
3927-3936 |
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| Abstract |
Automatic tree crown segmentation from remote sensing data is especially challenging in dense, diverse, and multilayered tropical forest canopies, and tracking mortality by this approach is even more difficult. Here, we examine the potential for combining airborne laser scanning (ALS) with multispectral and hyperspectral data to improve the accuracy of tree crown segmentation at a study site in French Guiana. We combined an ALS point cloud clustering method with a spectral deep learning model to achieve 83% accuracy at recognizing manually segmented reference crowns (with congruence >0.5). This method outperformed a two-step process that involved clustering the ALS point cloud and then using the logistic regression of hyperspectral distances to correct oversegmentation. We used this approach to map tree mortality from repeat surveys and show that the number of crowns identified in the first that intersected with height loss clusters was a good estimator of the number of dead trees in these areas. Our results demonstrate that multisensor data fusion improves the automatic segmentation of individual tree crowns and presents a promising avenue to study forest demography with repeated remote sensing acquisitions. |
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EcoFoG @ webmaster @ |
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1008 |
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| Author |
Campillo, F.; Rossi, V. |
| Title |
Convolution Particle Filter for Parameter Estimation in General State-Space Models |
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Journal Article |
| Year |
2009 |
Publication |
IEEE Transactions on Aerospace and Electronic Systems |
Abbreviated Journal |
IEEE Trans. Aerosp. Electron. Syst. |
| Volume |
45 |
Issue |
3 |
Pages |
1063-1072 |
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| Abstract |
The state-space modeling of partially observed dynamical systems generally requires estimates of unknown parameters. The dynamic state vector together with the static parameter vector can be considered as an augmented state vector. Classical filtering methods, such as the extended Kalman filter (EKF) and the bootstrap particle filter (PF), fail to estimate the augmented state vector. For these classical filters to handle the augmented state vector, a dynamic noise term should be artificially added to the parameter components or to the deterministic component of the dynamical system. However, this approach degrades the estimation performance of the filters. We propose a variant of the PF based on convolution kernel approximation techniques. This approach is tested on a simulated case study. |
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IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC |
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0018-9251 |
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ISI:000270225500017 |
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EcoFoG @ eric.marcon @ |
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194 |
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Essebtey, Salma El Idrissi ; Villard, Ludovic ; Borderies, Pierre ; Koleck, Thierry ; Burban, Benoït ; Le Toan, Thuy |
| Title |
Long-Term Trends of P-Band Temporal Decorrelation Over a Tropical Dense Forest-Experimental Results for the BIOMASS Mission |
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Journal Article |
| Year |
2021 |
Publication |
IEEE Transactions on Geoscience and Remote Sensing |
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| Volume |
60 |
Issue |
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Pages |
1-15 |
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Fostered by the upcoming BIOMASS mission, this article explores long-term trends of P-band temporal decorrelation over a tropical forest due to a time series of 617 days acquired during the TropiScat-2 experiment. The interest in this unique time series is twofold. First, it provides consistent statistics to monitor the yearly evolution of temporal coherences according to specific time scales of the BIOMASS tomographic and interferometric phases. Second, it provides key insights to explore new processing approaches with the combination of data from different orbit directions (ascending/descending) and different mission cycles separated by about seven months according to the current acquisition plan. For the first time, this study shows that 18-day coherences (corresponding to the time interval between the first and last acquisitions of the BIOMASS tomographic processing) can vary significantly according to rainy and dry seasons (medians from 0.3 to 0.9). The extension to time intervals of up to 90 days within both seasons and over two consecutive years puts forward the key role of the typical sporadic rainfalls occurring during dry periods in tropical rainforests, with a stronger impact on temporal coherence evolution compared to the more reproducible rainy seasons. Furthermore, outstanding values significantly above zero have been obtained for the 7- and 14-month coherences (medians of 0.35 and 0.2, respectively), opening the way to new methods of change detection. Overall, this study highlights the role of P-band temporal decorrelation not only as a disturbance factor for coherent applications but also as a relevant indicator of forest changes. |
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Institute of Electrical and Electronics Engineers |
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EcoFoG @ webmaster @ |
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1060 |
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| Author |
Hamadi, A.; Borderies, P.; Albinet, C.; Koleck, T.; Villard, L.; Ho Tong Minh, D.; Le Toan, T.; Burban, B. |
| Title |
Temporal coherence of tropical forests at P-band: Dry and rainy seasons |
Type |
Journal Article |
| Year |
2015 |
Publication |
IEEE Geoscience and Remote Sensing Letters |
Abbreviated Journal |
IEEE Geosci. Remote Sens. Lett. |
| Volume |
12 |
Issue |
3 |
Pages |
557-561 |
| Keywords |
Biomass mission; forest scattering; ground-based experiment; P-band; range impulse response; temporal coherence |
| Abstract |
In this letter, the temporal coherence of tropical forest scattering at P-band is addressed by means of a ground-based experiment. The study is based on the TropiScat campaign in French Guiana, designed to support the Biomass mission, which will be the ESA 7th Earth Explorer mission. For Biomass, temporal coherence is a crucial parameter for coherent processing of polarimetric synthetic aperture radar (SAR) interferometry and SAR tomography in repeat-pass acquisitions. During the experiment, data were continuously collected for six months during both the rainy and dry seasons. For the rain-free days in both seasons, the coherence exhibits a daily cycle showing a high decorrelation during daytime, which is likely due to motion in the canopy. Up to a 20-day baseline, the coherence is much higher in the dry season than in the rainy season (> 0.8). From 20 to 40 days, it presents the same order of magnitude in both seasons [0.6, 0.7]. For larger temporal baselines, it becomes lower in the dry season. The results can be used to assess the long-term coherence of repeat-pass observations over a tropical forest. However, an extension of this study to several years and over other forest spots would be necessary to draw more general conclusions. |
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EcoFogKourou, France |
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Institute of Electrical and Electronics Engineers Inc. |
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1545598x (Issn) |
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Export Date: 21 October 2014; Correspondence Address: Hamadi, A.; Centre d'Etudes Spatiales de la BiosphèreFrance; Funding Details: ESA, European Space Agency |
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no |
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EcoFoG @ webmaster @ |
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563 |
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| Author |
Ruelle, J.; Clair, B.; Beauchene, J.; Prevost, M.F.; Fournier, M. |
| Title |
Tension wood and opposite wood in 21 tropical rain forest species 2. Comparison of some anatomical and ultrastructural criteria |
Type |
Journal Article |
| Year |
2006 |
Publication |
IAWA Journal |
Abbreviated Journal |
IAWA J. |
| Volume |
27 |
Issue |
4 |
Pages |
341-376 |
| Keywords |
tension wood; opposite wood; tropical rain forest; vessels; wood anatomy; wood fibre |
| Abstract |
The anatomy of tension wood and opposite wood was compared in 21 tropical rain forest trees from 21 species belonging to 18 families from French Guyana. Wood specimens were taken from the upper and lower sides of naturally tilted trees. Measurement of the growth stress level ensured that the two samples were taken from wood tissues in a different mechanical state: highly tensile-stressed wood on the upper side, called tension wood and normally tensile-stressed wood on the lower side, called opposite wood. Quantitative parameters relating to fibres and vessels were measured on transverse sections of both tension and opposite wood to check if certain criteria can easily discriminate the two kinds of wood. We observed a decrease in the frequency of vessels in the tension wood in all the trees studied. Other criteria concerning shape and surface area of the vessels, fibre diameter or cell wall thickness did not reveal any general trend. At the ultrastructural level, we observed that the microfibril angle in the tension wood sample was lower than in opposite wood in all the trees except one (Licania membranacea). |
| Address |
UAG, ENGREF,UMR Ecol Forets Guyane, INRA,ECOFOG, CIRAD,CNRS, F-97379 Kourou, Guyana, Email: ruelle_j@kourou.cirad.fr |
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| Publisher |
INT ASSOC WOOD ANATOMISTS |
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0928-1541 |
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| Notes |
ISI:000242437400001 |
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no |
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EcoFoG @ eric.marcon @ |
Serial |
171 |
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Clair, B.; Ruelle, J.; Beauchene, J.; Prevost, M.F.; Fournier, M. |
| Title |
Tension wood and opposite wood in 21 tropical rain forest species 1. Occurrence and efficiency of the G-layer |
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Journal Article |
| Year |
2006 |
Publication |
IAWA Journal |
Abbreviated Journal |
IAWA J. |
| Volume |
27 |
Issue |
3 |
Pages |
329-338 |
| Keywords |
gelatinous layer; G-layer; French Guyana; tropical rain forest; tension wood; wood anatomy |
| Abstract |
Wood samples were taken from the upper and lower sides of 21 naturally tilted trees from 18 families of angiosperms in the tropical rain forest in French Guyana. The measurement of growth stresses ensured that the two samples were taken from wood tissues in a different mechanical state: highly tensile stressed wood on the upper side, called tension wood, and lower tensile stressed wood on the lower side, called opposite wood. Eight species had tension wood fibres with a distinct gelatinous layer (G-layer). The distribution of gelatinous fibres varied from species to species. One of the species, Casearia javitensis (Flacourtiaceae), showed a peculiar multilayered secondary wall in its reaction wood. Comparison between the stress level and the occurrence of the G-layer indicates that the G-layer is not a key factor in the production of high tensile stressed wood. |
| Address |
UAG, INRA, ENGREF, CIRAD CNRS,ECOFOG,UMR Ecol Forets Guyane, F-97379 Kourou, Guyana, Email: clair@lmgc.univ-montp2.fr |
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INT ASSOC WOOD ANATOMISTS |
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0928-1541 |
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| Notes |
ISI:000240542400008 |
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no |
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EcoFoG @ eric.marcon @ |
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176 |
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Clair, B.; Gril, J.; Baba, K.; Thibaut, B.; Sugiyama, J. |
| Title |
Precautions for the structural analysis of the gelatinous layer in tension wood |
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Journal Article |
| Year |
2005 |
Publication |
IAWA Journal |
Abbreviated Journal |
IAWA J. |
| Volume |
26 |
Issue |
2 |
Pages |
189-195 |
| Keywords |
artefact; fibre wall; gelatinous layer (G-layer); tension wood |
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The gelatinous layer (G-layer) of tension wood fibres in hardwood contributes to the mechanical function of the living tree and has significant consequences on properties of solid wood. Its size, shape and structure observed by optical or electron microscopy exhibits characteristic anatomical features. However, we found that sectioning of non-embedded wood samples results in an uncontrolled swelling of the G-layer. In order to assess this artefact, the shape and thickness of the G-layer was monitored by serial sections from an embedded wood sample, from its trimmed transverse face to that located several hundreds of micrometres deep. The results revealed that the initial cutting before embedding produced a border effect responsible for the swollen nature, which is similar to sections from non-embedded material. After a conventional embedding technique was applied, a section of at least 30 micrometres below the trimming surface is required to observe an un-swollen G-layer. |
| Address |
Kyoto Univ, Res Inst Sustainable Humanosphere, Lab Biomass Morphogenesis & Informat, Kyoto 6110011, Japan, Email: clair@blmgc.univ.montp2.fr |
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INT ASSOC WOOD ANATOMISTS |
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0928-1541 |
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ISI:000229698100003 |
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no |
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EcoFoG @ eric.marcon @ |
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254 |
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Clair, B.; Arinero, R.; Leveque, G.; Ramonda, M.; Thibaut, B. |
| Title |
Imaging the mechanical properties of wood cell wall layers by atomic force modulation microscopy |
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Journal Article |
| Year |
2003 |
Publication |
IAWA Journal |
Abbreviated Journal |
IAWA J. |
| Volume |
24 |
Issue |
3 |
Pages |
223-230 |
| Keywords |
wood; cell wall; mechanical properties; elastic modulus; tension wood |
| Abstract |
Atomic Force Microscopy in force modulation mode was used to study the elastic properties of the different fibre wall layers of the tension wood of holm oak and normal wood of boco. The method is based on the measurement of the resonance frequency of the microscope lever in contact with the sample. This frequency is related to the reduced Young modulus E* = E/(1-nu(2)) of the material, supposed to be isotropic. 'Elastic' images of the cell are obtained simultaneously with the topographic images, which allows the observation of the mechanical properties of the cells at a nanometric scale. Layers G, S-1, S-2 and ML can clearly be distinguished. By comparison with known materials an estimation of the absolute modulus is given in the range 5-20 GPa, but should be considered with caution, because the inherent anisotropy of the materials has not been taken into account. |
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Univ Montpellier 2, CNRS, UMR 5508, Lab Mecan & Genie Civil, F-34095 Montpellier, France |
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INT ASSOC WOOD ANATOMISTS |
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0928-1541 |
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ISI:000185049700003 |
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no |
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EcoFoG @ eric.marcon @ |
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270 |
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Guerrero, R.J.; Delabie, J.H.C.; Dejean, A. |
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Taxonomic Contribution to the aurita Group of the Ant Genus Azteca (Formicidae: Dolichoderinae) |
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Journal Article |
| Year |
2010 |
Publication |
Journal of Hymenoptera Research |
Abbreviated Journal |
J. Hymenopt. Res. |
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19 |
Issue |
1 |
Pages |
51-65 |
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| Abstract |
We describe five new species in the aurita group of the genus Azteca: Azteca andreae sp. n. (French Guiana), Azteca diabolica sp. n. (Panama), Azteca laurae sp. n. (Brazil), Azteca linamariae sp. n. (Brazil and Colombia) and Azteca snellingi sp. n. (Panama). Four of these new species are based on gynes, while the last is based only on the worker caste. All of them bear the aurita group characteristics. The second taxon is remarkable, as it differs from all of the other members of the group in the exaggerated, horn-like extensions of the posterolateral vertex margins. Azteca snellingi sp. n. is named in honor of our colleague, Roy Snelling, in tribute to his life-long contribution to knowledge of the world of Hymenoptera. A key to all known species of the aurita group, based on gynes, is provided. We report also for the first time an intercast case for the genus Azteca, based on an Azteca schimperi specimen. |
| Address |
[Guerrero, Roberto J.] Univ Magdalena, INTROPIC, Grp Invest Insectos Neotrop, Santa Marta, Magdalena, Colombia, Email: robertojoseguerreroflorez@gmail.com |
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INT SOC HYMENOPTERISTS |
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1070-9428 |
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ISI:000285775800005 |
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no |
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EcoFoG @ eric.marcon @ |
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279 |
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Schmitt, Sylvain ; Raevel, Valérie ; Réjou-Méchain, Maxime ; Ayyappan, Narayanan ; Balachandran, Natesan ; Barathan, Narayanan ; Rajashekar, Gopalakrishnan ; Munoz, François |
| Title |
Canopy and understorey tree guilds respond differently to the environment in an Indian rain forest |
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Journal Article |
| Year |
2021 |
Publication |
Journal of Végétation Science |
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| Volume |
32 |
Issue |
5 |
Pages |
e13075 |
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Questions Changes in the functional composition of tree communities along resource availability gradients have received attention, but it is unclear whether understorey and canopy guilds respond similarly to different light, biomechanical, and hydraulic constraints. Location An anthropically undisturbed, old-growth wet evergreen dipterocarp forest plot located in Karnataka State, India. Methods We measured leaf and wood traits of 89 tree species representing 99% of all individuals in a 10-ha permanent plot with varying topographic and canopy conditions inferred from Light Detection And Ranging (LiDAR) data. We assigned tree species to guilds of canopy and understorey species and assessed the variation of the guild-weighted means of functional-trait values with canopy height and topography. Results The functional-trait space did not differ between canopy and understorey tree species. However, environmental filtering led to significantly different functional composition of canopy and understorey guild assemblages. Furthermore, they responded differently along environmental gradients related to water, nutrients, light, and wind exposure. For example, the canopy guild responded to wind exposure while the understorey guild did not. Conclusions The pools of understorey and canopy species are functionally similar. However, fine-scale environmental heterogeneity impacts differently on these two guilds, generating striking differences in functional composition between understorey and canopy guild assemblages. Accounting for vertical guilds improves our understanding of forest communities' assembly processes. |
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International Association for Vegetation Science |
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EcoFoG @ webmaster @ |
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1038 |
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