Résumé
In this study, we propose a methodology to estimate the spatial distribution of destabilizing rock glaciers, with a focus on the French Alps. We mapped geomorphological features that can be typically found in cases of rock glacier destabilization (e.g. crevasses and scarps) using orthoimages taken from 2000 to 2013. A destabilization rating was assigned by taking into account the evolution of these mapped destabilization geomorphological features and by observing the surface deformation patterns of the rock glacier, also using the available orthoimages. This destabilization rating then served as input to model the occurrence of rock glacier destabilization in relation to terrain attributes and to spatially predict the susceptibility to destabilization at a regional scale. Significant evidence of destabilization could be observed in 46 rock glaciers, i.e. 10 % of the total active rock glaciers in the region. Based on our susceptibility model of destabilization occurrence, it was found that this phenomenon is more likely to occur in elevations around the 0 ◦C isotherm (2700–2900 m a.s.l.), on north-facing slopes, steep terrain (25 to 30◦) and flat to slightly convex topographies. Model performance was good (AUROC = 0.76), and the susceptibility map also performed well at reproducing observable patterns of destabilization. About 3 km2 of creeping permafrost, or 10 % of the surface occupied by active rock glaciers, had a high susceptibility to destabilization. Considering we observed that only half of these areas of creep are currently showing destabilization evidence, we suspect there is a high potential for future rock glacier destabilization within the French Alps.
Auteurs, date et publication :
Auteurs Marco Marcer , Charlie Serrano , Alexander Brenning , Xavier Bodin , Jason Goetz , Philippe Schoeneich
Publication : The Cryosphere
Date : 2019
Volume : 13
Issue : 1
Pages : 141-155
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Jacques Roy , François Tardieu , Michèle Tixier-Boichard , Ulrich Schurr
Publication : Nature Plants
Date : 2025
Volume : 3
Issue : 10
Pages : 756-758
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Knowledge of the jaguar population is needed in French Guiana that faces an increase of human-jaguar conflicts. We carried out a camera trap survey to assess jaguar local density and home range size in a preserved coastal area of French Guiana. We ran spatially explicit capture recapture (SECR) models. In our model, the scale parameter σ, that is linked to the home range size, was larger for males (σ = 3.87 ± 0.59 SE km) than for females (σ = 2.33 ± 0.30 SE km). The assessed jaguar density was 3.22 ± 0.87 SE ind. 100 km−2, which should be considered as an optimal density in a French Guiana coastal area.
Auteurs, date et publication :
Auteurs Matthis Petit , Thomas Denis , Ondine Rux , Cécile Richard-Hansen , Rachel Berzins
Publication : Mammalia
Date : 2018
Volume : 82
Issue : 2
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Leaf mass per area (LMA) and leaf equivalent water thickness (EWT) are key leaf functional traits providing information for many applications including ecosystem functioning modeling and fire risk management. In this paper, we investigate two common conclusions generally made for LMA and EWT estimation based on leaf optical properties in the near-infrared (NIR) and shortwave infrared (SWIR) domains: (1) physically-based approaches estimate EWT accurately and LMA poorly, while (2) statistically-based and machine learning (ML) methods provide accurate estimates of both LMA and EWT. Using six experimental datasets including broadleaf species samples of >150 species collected over tropical, temperate and boreal ecosystems, we compared the performances of a physically-based method (PROSPECT model inversion) and a ML algorithm (support vector machine regression, SVM) to infer EWT and LMA based on leaf reflectance and transmittance. We assessed several merit functions to invert PROSPECT based on iterative optimization and investigated the spectral domain to be used for optimal estimation of LMA and EWT. We also tested several strategies to select the training samples used by the SVM, in order to investigate the generalization ability of the derived regression models. We evidenced that using spectral information from 1700 to 2400 nm leads to strong improvement in the estimation of EWT and LMA when performing a PROSPECT inversion, decreasing the LMA and EWT estimation errors by 55% and 33%, respectively. The comparison of various sampling strategies for the training set used with SVM suggests that regression models show limited generalization ability, particularly when the regression model is applied on data fully independent from the training set. Finally, our results demonstrate that, when using an appropriate spectral domain, the PROSPECT inversion outperforms SVM trained with experimental data for the estimation of EWT and LMA. Thus we recommend that estimation of LMA and EWT based on leaf optical properties should be physically-based using inversion of reflectance and transmittance measurements on the 1700 to 2400 nm spectral range.
Auteurs, date et publication :
Auteurs J. -B. Féret , G. le Maire , S. Jay , D. Berveiller , R. Bendoula , G. Hmimina , A. Cheraiet , J. C. Oliveira , F. J. Ponzoni , T. Solanki , F. de Boissieu , J. Chave , Y. Nouvellon , A. Porcar-Castell , C. Proisy , K. Soudani , J. -P. Gastellu-Etchegorry , M. -J. Lefèvre-Fonollosa
Publication : Remote Sensing of Environment
Date : 2019
Volume : 231
Pages : 110959
Catégorie(s)
#ANR-Citation #CIRAD #CNRS #FORET ItatingaAuteurs, date et publication :
Auteurs Hugo Gruson
Publication : Methods in Ecology and Evolution
Date : 2025
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Soldanella alpina differing in leaf epidermal UV-A absorbance (DEA375), as measured with the Dualex, was investigated as a model alpine plant for the flavonoid (Flav) composition and concentration and for anatomical and pigment characteristics. In sun leaves, twenty-three flavones were characterised by their mass formula, their maximum absorption, their glycosylation, their methylation and dehydroxylation pattern. The flavones belonged to four subfamilies (tetra-hydroxy-flavones, penta-hydroxy-flavones, penta-hydroxy-methyl-flavones and tri-hydroxy-di-methoxy-flavones), abundant in sun and shade leaves. Their concentration was estimated by their absorption at 350 nm after HPLC separation. Sun leaves contained relatively higher contents of penta-hydroxy-methyl-flavones and shade leaves higher contents of tetra-hydroxy-flavones. The flavones were present mainly in vacuoles, all over the leaf. After shade-sun transfer, the content of most flavones increased, irrespective of the presence or absence of UV radiation. Highly significant correlations with the log-transformed DEA375 suggest that DEA375 can be readily applied to predict the flavone content of S. alpina leaves. Shade-sun transfer of leaves decreased the hydroxycinnamic acid (HCA) content, the mass-based chlorophyll (Chl) a+b content and the Chl/Carotenoid (Car) ratio but increased DEA375, and the Car content. Together with previously reported anatomical characteristics all these parameters correlated significantly with the DEA375. The Flav content is therefore correlated to most of the structural characteristics of leaf acclimation to light and this can be probed in situ by DEA375.
Auteurs, date et publication :
Auteurs Luc P. R. Bidel , Sylvie Meyer , Anne-Claire Talhouët , Xavier Baudin , Caroline Daniel , Guillaume Cazals , Peter Streb
Publication : Plant Physiology and Biochemistry
Date : 2020
Volume : 151
Pages : 10-20
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Christine Gehrig‐Downie , André Obregón , Jörg Bendix , S Robbert Gradstein
Publication : Biotropica
Date : 2025
Volume : 43
Issue : 5
Pages : 591-596
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Julian Donald , Pete Maxfield , Celine Leroy , MD Farnon Ellwood
Publication : Acta Oecologica
Date : 2025
Volume : 106
Pages : 103586
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Juan Sebastian Ulloa , Thierry Aubin , Diego Llusia , Charles Bouveyron , Jérôme Sueur
Publication : Ecological Indicators
Date : 2025
Volume : 90
Pages : 346-355
Catégorie(s)
#CNRS #FORET NouraguesRésumé
1. Tank bromeliads form a conspicuous, yet neglected freshwater habitat in Neotropical forests. Recent studies driven by interests in medical entomology, fundamental aspects of bromeliad ecology and experimental research on food webs have, however, prompted increasing interest in bromeliad aquatic ecosystems. As yet, there is nothing in the literature about the life histories and environmental drivers of invertebrate population dynamics in tank bromeliads. 2. Based on fortnightly samples taken over one year, size frequency plots and individual dry masses allowed us to establish the life cycles and growth rates of the dominant aquatic invertebrates in a common bromeliad species of French Guiana. Linear mixed-effect models and Mantel tests were used to predict changes in density, biomass, and growth rates in relation to temperature, rainfall, humidity and detrital resources. 3. Annual variations in invertebrate densities and biomasses could be described according to three types of distribution: unimodal, bimodal or almost constant. Despite seasonal variations, precipitation, temperature, relative humidity and detritus concentration accounted significantly for changes in density and biomass, but we found no significant responses in growth rates of most invertebrate species. Species rather displayed non-seasonal life cycles with overlapping cohorts throughout the year. There was also a trend for delayed abundance peaks among congeneric species sharing similar functional traits, suggesting temporal partitioning of available resources. 4. Beyond novel knowledge, quantitative information on life histories is important to predict foodweb dynamics under the influence of external forcing and self-organisation. Our results suggest that changes in species distribution that will affect population dynamics through biotic interactions in space and/or time could have greater effects on food webs and ecosystem functioning than changes in environmental factors per se.
Auteurs, date et publication :
Auteurs Olivier Dézerald , Céline Leroy , Bruno Corbara , Alain Dejean , Stanislas Talaga , Régis Céréghino
Publication : Freshwater Biology
Date : 2025
Volume : 62
Issue : 2
Pages : 229-242