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Investigating the role of wind disturbance in tropical forests through a forest dynamics model and satellite observations / E-Ping Rau (2022)  

Public Titre : Investigating the role of wind disturbance in tropical forests through a forest dynamics model and satellite observations Type de document : Thèse/HDR Auteurs : E-Ping Rau, Auteur ; Jérôme Chave, Directeur de thèse Editeur : Toulouse : Université de Toulouse 3 Paul Sabatier Année de publication : 2022 Importance : 184 p. Format : 21 x 30 cm Note générale : Bibliographie Thèse en vue de l'obtention du Doctorat de l'Université de Toulouse 3 Paul Sabatier Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] biomasse forestière [Termes IGN] canopée [Termes IGN] chablis (sylviculture) [Termes IGN] cyclone [Termes IGN] forêt tropicale [Termes IGN] Guyane française [Termes IGN] image Sentinel-SAR [Termes IGN] modèle dynamique [Termes IGN] perturbation écologique [Termes IGN] précipitation [Termes IGN] risque naturel [Termes IGN] sécheresse [Termes IGN] traitement d'image radar [Termes IGN] vent Index. décimale : THESE Thèses et HDR Résumé : (Auteur) Natural disturbances have an important influence on the structure, composition and functioning of tropical forests and a role in the regulation of biogeochemical cycles. The frequency and intensity of natural disturbances are modified by climate change: a better knowledge of their mechanism of action is necessary to predict the consequences of this modification. Modeling allows us to evaluate the role of each of the ecological processes and their link with environmental factors. Remote sensing tools inform us about the structure and functioning of forests at large scales, and can be useful for the calibration and validation of vegetation models. In this thesis, I employed both approaches to examine how tropical forests are shaped by natural disturbances, particularly wind, which is a major disturbance factor in many tropical regions. First, I evaluated the transferability of a spatially explicit, individual-based model via sensitivity testing and calibration of global parameters. The model correctly predicts forest structure at two contrasting sites, and its response is consistent with variations in climate forcing. Calibration of a small number of key parameters was required, including the parameter controlling mortality and crown allometry. To investigate the sensitivity of the model to mortality, I implemented a wind damage module based on biophysical principles and coupled with wind speed to model forest responses to extreme wind events. With increasing disturbance level, canopy height decreased steadily but biomass showed a non-linear response. Wind intensity had a strong impact on canopy height and biomass, but not the frequency of extreme wind events. Finally, I tested whether radar data from Sentinel-1 satellites could be used to detect gaps due to natural disturbances in French Guiana. The Sentinel-1 data detected more natural gaps above 0.2 ha than the optical satellite data, and they showed a spatial pattern consistent with the optical images. The level of disturbance did not vary with altitude. We found more disturbance during dry seasons, which could be due to the delayed response of precipitation rather than the direct response of drought. In conclusion, this thesis demonstrates that the integration between modeling and remote sensing sheds light on the effects of natural disturbances on tropical forests. The resulting results can be used to study other types of disturbances and their interactions on a large scale. Note de contenu : General introduction General methods 1: Transferability of an individual- and trait-based forest dynamics model: a test case across the tropics 1.1 Abstract 1.2 Introduction 1.3 Materials and methods 1.4 Results 1.5 Discussion 1.6 Acknowledgements and author contributions 1.7 Supplementary data 2: Wind speed controls forest structure in subtropical forests exposed to cyclones: a case study using an individual-based model 2.1 Abstract 2.2 Introduction 2.3 Material and methods 2.4 Results 2.5 Discussion 2.6 Acknowledgments and author contributions 2.7 Supplementary data 3: Detecting Natural Disturbances in Tropical Forests Using Sentinel-1 SAR Data: a Test in French Guiana 3.1 Abstract 3.2 Introduction 3.3 Methods 3.4 Results 3.5 Discussions 3.6 Acknowledgments and author contributions 3.7 Supplementary data General discussion and conclusions Numéro de notice : 26836 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Thèse française Note de thèse : Thèse de Doctorat : Ecologie, biodiversité et évolution : Toulouse 3 : 2022 nature-HAL : Thèse DOI : sans Date de publication en ligne : 20/06/2022 En ligne : https://tel.hal.science/tel-03699667 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101075

Mapping tropical forest trees across large areas with lightweight cost-effective terrestrial laser scanning / Shengli Tao in Annals of Forest Science, vol 78 n° 4 (December 2021)  

Public [article]  inAnnals of Forest Science > vol 78 n° 4 (December 2021) . - n° 103 Titre : Mapping tropical forest trees across large areas with lightweight cost-effective terrestrial laser scanning Type de document : Article/Communication Auteurs : Shengli Tao, Auteur ; Nicolas Labrière, Auteur ; Kim Calders, Auteur ; Fabian Jörg Fischer, Auteur ; E-Ping Rau, Auteur ; Laetitia Plaisance, Auteur ; Jérôme Chave, Auteur Année de publication : 2021 Article en page(s) : n° 103 Note générale : bibliographie This work has benefitted from an “Investissement d'Avenir” grant managed by Agence Nationale de la Recherche (AnaEE France ANR-11-INBS-0001; CEBA, ref. ANR-10-LABX-25–01), the CNRS Nouragues station, and a CNES postdoctoral fellowship granted to S.T. Langues : Anglais (eng) Descripteur : [Termes IGN] diamètre à hauteur de poitrine [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] forêt tropicale [Termes IGN] Guyane (département français) [Termes IGN] inventaire forestier (techniques et méthodes) [Termes IGN] placette d'échantillonnage [Termes IGN] volume en bois [Vedettes matières IGN] Inventaire forestier Résumé : (auteur) Key message : We used lightweight terrestrial laser scanning (TLS) to detect over 3000 stems per hectare across a 12-ha permanent forest plot in French Guiana, 81% of them  Context : Accurate position mapping of tropical rainforest trees is crucial for baseline studies of tropical forest ecology but is labor-intensive. Terrestrial lidar scanning (TLS) is broadly used in temperate forest inventories, but its use in rainforests is restricted to the determination of individual tree volumes within small survey areas. Aims : Mapping tree stems across one large (12-ha) rainforest plot, including trees less than 10 cm DBH, and evaluating the precision of traditional mapping approaches. Methods : We used lightweight TLS, co-registered the acquisitions, and developed a new efficient algorithm to process the TLS data. Results : We detected 36,422 stems of which 29,665 (81%) were  Conclusion : Lightweight TLS technology is a promising tool for the estimation of stem tapering and volume. Here, we show that it also facilitates the establishment of large tropical forest inventories, by improving the positioning of trees, thus increasing the accuracy of forest inventories and their cost-effectiveness. Numéro de notice : A2021-954 Affiliation des auteurs : non IGN Thématique : FORET/IMAGERIE Nature : Article DOI : 10.1007/s13595-021-01113-9 Date de publication en ligne : 28/12/2021 En ligne : https://doi.org/10.1007/s13595-021-01113-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99998 [article]