Auteurs, date et publication :
Auteurs Francois Catzeflis , Marie-ka Tilak
Publication : Mammalia
Date : 2025
Volume : 73
Issue : 3
Pages : 239-247
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Sebastian C Treitli , Michael Kotyk , Naoji Yubuki , Eliška Jirounková , Jitka Vlasáková , Pavla Smejkalová , Petr Šípek , Ivan Čepička , Vladimír Hampl
Publication : Protist
Date : 2025
Volume : 169
Issue : 5
Pages : 744-783
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs L. M. San Jose
Date : 1970
Catégorie(s)
#CNRS #Metatron terrestreRésumé
Abstract. The surface temperature controls the temporal evolution of the snowpack, playing a key role in metamorphism and snowmelt. It shows large spatial variations in mountainous areas because the surface energy budget is affected by the topography, for instance because of the modulation of the short-wave irradiance by the local slope and the shadows and the short-wave and long-wave re-illumination of the surface from surrounding slopes. These topographic effects are often neglected in large-scale models considering the surface to be flat and smooth. Here we aim at estimating the surface temperature of snow-covered mountainous terrain in clear-sky conditions in order to evaluate the relative importance of the different processes that control the spatial variations. For this, a modelling chain is implemented to compute the surface temperature in a kilometre-wide area from local radiometric and meteorological measurements at a single station. The first component of this chain is the Rough Surface Ray-Tracing (RSRT) model. Based on a photon transport Monte Carlo algorithm, this model quantifies the incident and reflected short-wave radiation on every facet of the mesh describing the snow-covered terrain. The second component is a surface scheme that estimates the terms of the surface energy budget from which the surface temperature is eventually estimated. To assess the modelling chain performance, we use in situ measurements of surface temperature and satellite thermal observations (Landsat 8) in the Col du Lautaret area, in the French Alps. The results of the simulations show (i) an agreement between the simulated and measured surface temperature at the station for a diurnal cycle in winter within 0.2 ∘C; (ii) that the spatial variations in surface temperature are on the order of 5 to 10 ∘C in the domain and are well represented by the model; and (iii) that the topographic effects ranked by importance are the modulation of solar irradiance by the local slope, followed by the altitudinal variations in air temperature (lapse rate), the re-illumination by long-wave thermal emission from surrounding terrain, and the spectral dependence of snow albedo. The changes in the downward long-wave flux because of variations in altitude and the absorption enhancement due to multiple bounces of photons in steep terrain play a less significant role. These results show the necessity of considering the topography to correctly assess the energy budget and the surface temperature of snow-covered complex terrain.
Auteurs, date et publication :
Auteurs Alvaro Robledano , Ghislain Picard , Laurent Arnaud , Fanny Larue , Inès Ollivier
Publication : The Cryosphere
Date : 2022
Volume : 16
Issue : 2
Pages : 559-579
Catégorie(s)
#CNRS #Lautaret #UGARésumé
DNA metabarcoding from the ethanol used to store macroinvertebrate bulk samples is a convenient methodological option in molecular biodiversity assessment and biomonitoring of aquatic ecosystems, as it preserves specimens and reduces problems associated with sample sorting. However, this method may be affected by errors and biases, which need to be thoroughly quantified before it can be mainstreamed into biomonitoring programmes. Here, we used 80 unsorted macroinvertebrate samples collected in Portugal under a Water Framework Directive monitoring programme, to compare community diversity and taxonomic composition metrics estimated through morphotaxonomy versus metabarcoding from storage ethanol using three markers (COI-M19BR2, 16S-Inse01 and 18S-Euka02) and a multimarker approach. A preliminary in silico analysis showed that the three markers were adequate for the target taxa, with detection failures related primarily to the lack of adequate barcodes in public databases. Metabarcoding of ethanol samples retrieved far less taxa per site (alpha diversity) than morphotaxonomy, albeit with smaller differences for COI-M19BR2 and the multimarker approach, while estimates of taxa turnover (beta diversity) among sites were similar across methods. Using generalized linear mixed models, we found that after controlling for differences in read coverage across samples, the probability of detection of a taxon was positively related to its proportional abundance, and negatively so to the presence of heavily sclerotized exoskeleton (e.g., Coleoptera). Overall, using our experimental protocol with different template dilutions, the COI marker showed the best performance, but we recommend the use of a multimarker approach to detect a wider range of taxa in freshwater macroinvertebrate samples. Further methodological development and optimization efforts are needed to reduce biases associated with body armouring and rarity in some macroinvertebrate taxa.
Auteurs, date et publication :
Auteurs Filipa M. S. Martins , Miguel Porto , Maria J. Feio , Bastian Egeter , Aurélie Bonin , Sónia R. Q. Serra , Pierre Taberlet , Pedro Beja
Publication : Molecular Ecology
Date : 2025
Volume : 30
Issue : 13
Pages : 3221-3238
Catégorie(s)
#CNRS #eDNARésumé
Abstract. Climatic drivers limit several important physiological processes involved in ecosystem carbon dynamics including gross primary productivity (GPP) and carbon allocation in vegetation. Climatic variability limits these two processes differently. We developed an existing mechanistic model to analyse photosynthesis and variability in carbon allocation in two evergreen species at two Mediterranean forests. The model was calibrated using a combination of eddy covariance CO2 flux data, dendrochronological time series of secondary growth and forest inventory data. The model was modified to be climate explicit in the key processes addressing the acclimation of photosynthesis and the pattern of C allocation, particularly to water stress. It succeeded in fitting both the high- and the low-frequency response of stand GPP and carbon allocation to stem growth. This would support its capability to address both C-source and C-sink limitations. Simulations suggest a decrease in mean stomatal conductance in response to a recent enhancement in water stress and an increase in mean annual intrinsic water use efficiency (iWUE) in both species during the last 50 years. However, this was not translated into a parallel increase in ecosystem water use efficiency (WUE). The interannual variability in WUE closely followed that in iWUE at both sites. Nevertheless, long-term decadal variability in WUE followed the long-term decrease in annual GPP matching the local trend in annual precipitation observed since the late 1970s at one site. In contrast, at the site where long-term precipitation remained stable, GPP and WUE did not show a negative trend and the trees buffered the climatic variability. In our simulations these temporal changes were related to acclimation processes at the canopy level, including modifications in LAI and stomatal conductance, but also partly related to increasing [CO2] because the model includes biochemical equations where photosynthesis is directly linked to [CO2]. Long-term trends in GPP did not match those in growth, in agreement with the C-sink hypothesis. The model has great potential for use with abundant dendrochronological data and analyse forest performance under climate change. This would help to understand how different interfering environmental factors produce instability in the pattern of carbon allocation and, hence, the climatic signal expressed in tree rings.
Auteurs, date et publication :
Auteurs G. Gea-Izquierdo , F. Guibal , R. Joffre , J. M. Ourcival , G. Simioni , J. Guiot
Publication : Biogeosciences
Date : 2015
Volume : 12
Issue : 12
Pages : 3695-3712
Catégorie(s)
#CNRS #FORET FontBlanche #FORET Puechabon #INRAEAuteurs, date et publication :
Auteurs Olivier Boissier , François Feer , Pierre‐yves Henry , Pierre‐Michel Forget
Publication : Ecological Applications
Date : 2025
Catégorie(s)
#CNRS #FORET NouraguesRésumé
The determination of ecosystem carbon balances is a major issue in environmental research. Forest inventories and – more recently – Eddy covariance measurements have been set up to guide sustainability assessments as well as carbon accounting. A differentiation between ecosystem compartments of carbon such as soil and vegetation, or above- and belowground storages nevertheless requires further empirical assumptions or model simulations. However, models to estimate carbon balances often do not account for carbon export by management and the direct and indirect impacts of forest management. To overcome this obstacle, we complemented a physiologically based process model (MoBiLE-PSIM) with routines for dimensional tree growth and mortality and evaluated the full model with measurements of water availability, primary production, respiration fluxes and forest development (tree dimensions and numbers per hectare).
Auteurs, date et publication :
Auteurs Rüdiger Grote , Ralf Kiese , Thomas Grünwald , Jean-Marc Ourcival , André Granier
Publication : Agricultural and Forest Meteorology
Date : 2025
Pages : 12
Catégorie(s)
#CNRS #FORET PuechabonAuteurs, date et publication :
Auteurs J. Pottier , Z. Malenovsky , A. Psomas , L. Homolova , M. E. Schaepman , P. Choler , W. Thuiller , A. Guisan , N. E. Zimmermann
Publication : Biology Letters
Date : 2014
Volume : 10
Issue : 7
Pages : 20140347-20140347
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Bradley Z. Carlson , Philippe Choler , Julien Renaud , Jean-Pierre Dedieu , Wilfried Thuiller
Publication : Annals of Botany
Date : 2025
Volume : 116
Issue : 6
Pages : 1023-1034