Résumé
Gravitropic movements in angiosperm woody stems are achieved through the action of bark and/or wood motor, depending on the bark and wood fibre anatomy (with trellis structure or not; with G-layers or not). Bark motor is as efficient as wood motor to recover from tilting in young trees of 21 tropical species.
Auteurs, date et publication :
Auteurs Barbara Ghislain , Tancrède Alméras , Jonathan Prunier , Bruno Clair
Publication : Annals of Forest Science
Date : 2019
Volume : 76
Issue : 4
Pages : 107
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term tem-perature response, and even minor differences in the shape of the response curve can significantly impact estimates of ecosystem carbon release and/or storage. Given this, it is critical to establish whether there are predictable patterns in the shape of the respiration–temper-ature response curve, and thus in the intrinsic temperature sensitivity of respiration across the globe. Analyzing measurements in a compre-hensive database for 231 species spanning 7 biomes, we demonstrate that temperature-dependent increases in leaf respiration do not follow a commonly used exponential function. Instead, we find a decelerating function as leaves warm, reflecting a declining sensitivity to higher temperatures that is remarkably uniform across all biomes and plant functional types. Such convergence in the temperature sensitivity of leaf respiration suggests that there are universally applicable controls on the temperature response of plant energy metabolism, such that a single new function can predict the temperature dependence of leaf respiration for global vegetation. This simple function enables straight-forward description of plant respiration in the land-surface compo-nents of coupled earth system models. Our cross-biome analyses shows significant implications for such fluxes in cold climates, gener-ally projecting lower values compared with previous estimates. temperature sensitivity | climate models | carbon exchange | Q 10 |
Auteurs, date et publication :
Auteurs Mary A Heskel , Odhran S O 'sullivan , Peter B Reich , Mark G Tjoelker , Lasantha K Weerasinghe , Aurore Penillard , John J G Egerton , Danielle Creek , Keith J Bloomfield , Jen Xiang , Felipe Sinca , Zsofia R Stangl , Alberto Martinez-De La Torre , Kevin L Griffin , Chris Huntingford , Vaughan Hurry , Patrick Meir , Matthew H Turnbull , Owen K Atkin
Publication : Proceeding of the National Academy of Sciences USA
Date : 2025
Volume : 113
Issue : 14
Pages : 3832–3837
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Christopher Baraloto , Bruno Hérault , C. E. Timothy Paine , Hélène Massot , Lilian Blanc , Damien Bonal , Jean-François Molino , Eric A. Nicolini , Daniel Sabatier
Publication : Journal of Applied Ecology
Date : 2012
Volume : 49
Issue : 4
Pages : 861–870
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Adriane Esquivel-Muelbert , Timothy R. Baker , Kyle G. Dexter , Simon L. Lewis , Roel J. W. Brienen , Ted R. Feldpausch , Jon Lloyd , Abel Monteagudo-Mendoza , Luzmila Arroyo , Esteban Álvarez-Dávila , Niro Higuchi , Beatriz S. Marimon , Ben Hur Marimon-Junior , Marcos Silveira , Emilio Vilanova , Emanuel Gloor , Yadvinder Malhi , Jerôme Chave , Jos Barlow , Damien Bonal
Publication : Global Change Biology
Date : 2018
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The structure of forests is an important indicator of ecosystem dynamics and enables the modeling and monitoring of ecological change. Synthetic aperture radar tomography (TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. Due to the advantages of superresolution imaging and a small number of measurements, compressive sensing (CS) inversion techniques for SAR tomography were successfully developed and applied. This paper addresses the 3-D imaging of forested areas based on the framework of CS using fully polarimetric (FP) multibaseline SAR interferometric (MB-InSAR) tomography at P-band. A new CS-based FP MB-InSAR tomography method is proposed: a sum of Kronecker product (SKP) decomposition-based CS FP MB-InSAR tomography method (FP-SKPCS TomoSAR method). The method, based on an assumption that the reflectivity signal of a single scattering mechanism (SM) is more sparse than that of a composite of SMs, recovers the reflectivity profile of different SMs by using the CS technique. This method not only allows superresolution imaging with a low number of acquisitions but also can estimate the polarimetric SM of the vertical structure of forested areas. The effectiveness of these novel techniques for polarimetric SAR tomography is demonstrated using FP P-band airborne data sets acquired by the ONERA SETHI airborne system over a test site in Paracou, French Guiana, and the results of the vertical structure of forested areas derived by the method are verified by in situ test data.
Auteurs, date et publication :
Auteurs Xinwu Li , Lei Liang , Huadong Guo , Yue Huang
Publication : IEEE Transactions on Geoscience and Remote Sensing
Date : 2016
Volume : 54
Issue : 1
Pages : 153–166
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Global environmental change necessitates increased predictive capacity; for forests, recent advances in technology provide the response to this challenge. “Next‐generation” remote‐sensing instruments can measure forest biogeochemistry and structural change, and individual‐based models can predict the fates of vast numbers of simulated trees, all growing and competing according to their ecological attributes in altered environments across large areas. Application of these models at continental scales is now feasible using current computing power. The results obtained from individual‐based models are testable against remotely sensed data, and so can be used to predict changes in forests at plot, landscape, and regional scales. This model–data comparison allows the detailed prediction, observation, and testing of forest ecosystem changes at very large scales and under novel environmental conditions, a capability that is greatly needed in this time of potentially massive ecological change.
Auteurs, date et publication :
Auteurs Herman H Shugart , Gregory P Asner , Rico Fischer , Andreas Huth , Nikolai Knapp , Thuy Le Toan , Jacquelyn K Shuman
Publication : Frontiers in Ecology and the Environment
Date : 2015
Volume : 13
Issue : 9
Pages : 503–511
Catégorie(s)
#CIRAD #FORET ParacouRésumé
textlessptextgreater Within tree communities, the differential use of soil N mineral resources, a key factor in ecosystem functioning, may reflect functional complementarity, a major mechanism that could explain species coexistence in tropical rainforests. textlessitalictextgreaterEperua falcatatextless/italictextgreater and textlessitalictextgreaterDicorynia guianensistextless/italictextgreater , two abundant species cooccurring in rainforests of French Guiana, were chosen as representative of two functional groups with complementary N uptake strategies (contrasting leaf textlessitalictextgreaterδtextless/italictextgreater textlesssuptextgreater15textless/suptextgreater N signatures related to the textlessitalictextgreaterδtextless/italictextgreater textlesssuptextgreater15textless/suptextgreater N of their soil N source, textlessmath id="M1"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNOtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater3textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater-textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater or textlessmath id="M2"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNHtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater4textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater+textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater ). The objectives were to investigate if these strategies occurred under contrasted soil N resources in sites with distinct geological substrates representative of the coastal rainforests. Results showed that species displayed contrasting leaf textlessitalictextgreaterδtextless/italictextgreater textlesssuptextgreater15textless/suptextgreater N signatures on both substrates, confirming their complementary N uptake strategy. Consequently, their leaf textlesssuptextgreater15textless/suptextgreater N can be used to trace the presence of inorganic N-forms in soils ( textlessmath id="M3"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNHtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater4textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater+textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater and textlessmath id="M4"textgreater textlessmrowtextgreater textlessmsuptextgreater textlessmrowtextgreater textlessmrowtextgreater textlessmtexttextgreaterNOtextless/mtexttextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmn mathvariant="normal"textgreater3textless/mntextgreater textless/mrowtextgreater textless/mrowtextgreater textlessmrowtextgreater textlessmotextgreater-textless/motextgreater textless/mrowtextgreater textless/msuptextgreater textless/mrowtextgreater textless/mathtextgreater ) and thus to indicate the capacity of soils to provide each of these two N sources to the plant community. textless/ptextgreater
Auteurs, date et publication :
Auteurs J. C. Roggy , H. Schimann , D. Sabatier , J. F. Molino , V. Freycon , Anne-Marie Domenach
Publication : International Scholarly Research Notices
Date : 2014
Volume : 2014
Pages : 1–6
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Synthetic aperture radar Tomography (TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. However, the more multi-baselines acquisition, the longer the time span of acquisition, which will result in serious temporal decorrelation in forested area. In this way, we expect to use as smaller number of baselines as possible to obtain high estimation accuracy in elevation direction. We thus investigate the performance of Polarimetric SAR tomography (Pol-TomoSAR) with small number of baselines in forested areas. The results show that compressive sensingbased Pol-TomoSAR has higher estimation accuracy in elevation direction than conventional Pol-TomoSAR with small number of baselines.
Auteurs, date et publication :
Auteurs Lei Liang , Chenghu Zhou , Xinwu Li , Xizhang Gao , Wenjin Wu
Publication : Chinese Journal of Electronics
Date : 2019
Volume : 28
Issue : 5
Pages : 1073-1079
Catégorie(s)
#CIRAD #FORET ParacouRésumé
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 ParacouAuteurs, 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