Résumé
Backgrounds and Aims Leaf functional traits have been used as a basis to categoize plants across a range of resource-use specialization, from those that conserv
Auteurs, date et publication :
Auteurs Fabrice Grassein , Servane Lemauviel-Lavenant , Sandra Lavorel , Michael Bahn , Richard D. Bardgett , Marie Desclos-Theveniau , Philippe Laîné
Publication : Annals of Botany
Date : 2015
Volume : 115
Issue : 1
Pages : 107-115
Catégorie(s)
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Auteurs Florian C. Boucher , Wilfried Thuiller , Cristina Roquet , Rolland Douzet , Serge Aubert , Nadir Alvarez , Sébastien Lavergne
Publication : Evolution
Date : 2025
Volume : 66
Issue : 4
Pages : 1255-1268
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Francesco de Bello , Sandra Lavorel , Cécile H. Albert , Wilfried Thuiller , Karl Grigulis , Jiři Dolezal , Štepán Janeček , Jan Lepš
Publication : Methods in Ecology and Evolution
Date : 2025
Volume : 2
Issue : 2
Pages : 163-174
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Mapping snow conditions in alpine areas is crucial for monitoring local hydrology to support water resource management decisions. Recently, the use of structure‐from‐motion multiview stereo 3‐D reconstruction (or SFM photogrammetry) to derive high‐resolution digital elevation models (DEMs) has become popular for mapping snow depth in alpine areas. In this study, methods for communicating spatial uncertainties in snow depth calculated from SFM‐derived DEMs are presented using a case study in the French Alps. A spatially varying snow depth precision estimate was determined using an error propagation model based on the precision of the acquired SFM DEMs, which was obtained from repeated unmanned aerial vehicle flights. Spatially varying snow depth detection limits were determined using Student's t distribution. It was found that snow depths as shallow as 1 to 5 cm could be detected with high confidence for most of the study area. Areas of high uncertainties were generally related to where the extent of the ground control coverage did not match in the snow‐on and snow‐off surveys and in areas with higher surface roughness. A map of the snow depth detection threshold was found to be useful for identifying areas with high uncertainties and potential biases in the SFM snow depths, such as errors due to changes in topography between DEM acquisition dates and poor SFM reconstruction.
Auteurs, date et publication :
Auteurs Jason Goetz , Alexander Brenning
Publication : Water Resources Research
Date : 2025
Volume : 55
Issue : 9
Pages : 7772-7783
Catégorie(s)
#CNRS #Lautaret #UGARésumé
In the Caryophyllaceae, seed surfaces contain cell protrusions, of varying sizes and shapes, called tubercles. Tubercles have long been described in many species, but quantitative analyses with measurements of size and shape are lacking in the literature. Based on optical photography, the seeds of Silene were classified into four types: smooth, rugose, echinate and papillose. Seeds in each of these groups have characteristic geometrical properties: smooth seeds lack tubercles and have the highest values of circularity and solidity in their lateral views, while papillose seeds have the largest tubercles and lowest values of circularity and solidity both in lateral and dorsal views. Here, tubercle width, height and slope, maximum and mean curvature values and maximum to mean curvature ratio were obtained for representative seeds of a total of 31 species, 12 belonging to Silene subg. Behenantha and 19 to S. subg. Silene. The seeds of the rugose type had lower values of curvature. Additionally, lower values of curvature were found in species of S. subg. Silene in comparison with S. subg. Behenantha. The seeds of S. subg. Behenantha had higher values of tubercle height and slope and higher values of maximum and average curvature and maximum to mean curvature ratio.
Auteurs, date et publication :
Auteurs José Luis Rodríguez-Lorenzo , José Javier Martín-Gómez , Ana Juan , Ángel Tocino , Emilio Cervantes
Publication : Plants
Date : 2023
Volume : 12
Issue : 19
Pages : 3444
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Abstract. The presence of light-absorbing particles (LAPs) in snow leads to a decrease in short-wave albedo affecting the surface energy budget. However, the understanding of the impacts of LAPs is hampered by the lack of dedicated datasets, as well as the scarcity of models able to represent the interactions between LAPs and snow metamorphism. The present study aims to address both these limitations by introducing a survey of LAP concentrations over two snow seasons in the French Alps and an estimation of their impacts based on the Crocus snowpack model that represents the complex interplays between LAP dynamics and snow metamorphism.
First, a unique dataset collected at Col du Lautaret (2058 m a.s.l., above sea level, French Alps) for the two snow seasons 2016–2017 and 2017–2018 is presented. This dataset consists of spectral albedo measurements, vertical profiles of snow specific surface area (SSA), density and concentrations of different LAP species. Spectral albedos are processed to estimate SSA and LAP absorption-equivalent concentrations near the surface of the snowpack. These estimates are then compared to chemical measurements of LAP concentrations and SSA measurements. Our dataset highlights, among others, large discrepancies between two measurement techniques of black carbon (BC) concentrations in snow (namely thermal-optical and laser-induced incandescence).
Second, we present ensemble snowpack simulations of the multi-physics version of the detailed snowpack model Crocus, forced with in situ meteorological data, as well as dust and BC deposition fluxes from an atmospheric model. The temporal variations of near-surface LAP concentrations and SSA are most of the time correctly simulated. The simulated seasonal radiative forcing of LAPs is 33 % higher for the 2017–2018 snow season than for the 2016–2017 one, highlighting a strong variability between these two seasons. However, the shortening of the snow season caused by LAPs is similar with 10 ± 5 and 11 ± 1 d for the first and the second snow seasons, respectively. This counter-intuitive result is attributed to two small snowfalls at the end of the first season and highlights the importance in accounting for meteorological conditions to correctly predict the impact of LAPs. The strong variability of season shortening caused by LAPs in the multi-physics ensemble for the first season (10 ± 5 d) also points out the sensitivity of model-based estimations of LAP impact on modelling uncertainties of other processes. Finally, the indirect impact of LAPs (i.e. the enhancement of energy absorption due to the acceleration of the metamorphism by LAPs) is negligible for the 2 years considered here, which is contrary to what was found in previous studies for other sites.
Auteurs, date et publication :
Auteurs François Tuzet , Marie Dumont , Ghislain Picard , Maxim Lamare , Didier Voisin , Pierre Nabat , Mathieu Lafaysse , Fanny Larue , Jesus Revuelto , Laurent Arnaud
Publication : The Cryosphere
Date : 2020
Volume : 14
Issue : 12
Pages : 4553-4579
Catégorie(s)
#CNRS #Lautaret #UGARésumé
The landscapes of the Vallon de la Route and Vallon de Pradieu (France) display typical geomorphological features of the Southern French Alps, with very few or no glaciers but a wide periglacial belt that extends from 2500 to 3100 m a.s.l. These valleys are unusual in that they contain several generations of rock glaciers that, from their rooting zone to their front, have developed in a topoclimatic setting characterised by high mean insolation (southerly aspect) and relatively low altitude. In this work, we determined the present status of these landforms, and more precisely the characteristics of the icy layers within the rock glaciers, via electrical soundings and thermal measurements, which we then combined with field observations. The permafrost zones in both areas are highly fragmented, whereas ground-ice can be present in landforms previously assumed as relict on the basis of their geomorphological characteristics alone. We used an empirical relationship between rock glacier flow velocity and terrain slope to estimate the time needed for both rock glacier assemblages to reach their present size. Our analyses therefore provide at the same time a broad relative chronological framework of the landscape setting up together with an overview of the spatial patterns of ice-rich permafrost features. It also suggests a number of hypotheses for the development of these landforms; however, further work involving more accurate dating methods is required to constrain these hypotheses.
Auteurs, date et publication :
Auteurs Xavier Bodin
Publication : Geografia Fisica e Dinamica Quaternaria
Date : 2025
Volume : 36
Issue : 2
Pages : pp. 27-28
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Climate change will increase the level of drought stress experienced by plant communities, but the spatial distribution of projected changes in dryness remains highly uncertain. Species can, to some extent, deal with climate uncertainty through natural variation in adaptive responses to environmental heterogeneity and predictability. Biodiversity conservation could thus target populations pre-adapted to climatic heterogeneity to anticipate climate uncertainty. Disentangling adaptive evolution of trait means versus trait plasticity, however, requires a sampling design with genetic replicates grown under distinct environmental conditions. Here, we applied three soil moisture treatments to genetic replicates of Fragaria vesca plants raised from seeds that were sampled in distinct topographical settings, to study adaptive trait and plasticity divergence in response to drought. We demonstrate that various plant traits evolved along distinct topographical gradients. Populations on south-exposed slopes, for example, retained high levels of both flowering and runner formation under drought stress, while north-faced populations hardly flowered under reduced soil moisture levels. Aspect but not elevation was found to coincide with variation in plant traits, suggesting that microenvironmental variation rather than general clines in elevation drive evolution in mountainous landscapes. Our results also indicate that traits and their plasticity can evolve independently in response to distinct topographical stressors. Synthesis. We conclude that heterogeneous landscapes (a) harbour micro-refugia of adaptive genetic diversity that protect natural populations against environmental change, and (b) represent invaluable sources of quantitative genetic variation that could support conservation where climate projections are inconclusive.
Auteurs, date et publication :
Auteurs Hanne De Kort , Bart Panis , Kenny Helsen , Rolland Douzet , Steven B. Janssens , Olivier Honnay
Publication : Journal of Ecology
Date : 2025
Volume : 108
Issue : 4
Pages : 1465-1474
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous persistent organic pollutants that accumulate in soils because of their high affinity for soil organic matter (SOM). As these pollutants are toxic to humans and the environment, a better understanding of their fate in the environment is required. This study aimed to assess the PAH distribution within soils according to different soil fractions: the free particulate organic matter (fPOM), the occluded particulate organic matter (oPOM) and the mineral-associated organic matter (MaOM). PAH contents were measured in bulk soils and SOM fractions of alpine soils along an elevation gradient in the French Alps (Lautaret) from 1920 m to 2840 m a.s.l. A specific PAH distribution was identified, with highest PAH contents in the oPOM, followed by the fPOM, then the MaOM. Organic matter (OM) contents of each fraction can partly explain this distribution, but results of nuclear magnetic resonance (NMR) spectroscopy on fPOM and oPOM also highlighted a correlation between the PAH contents and the degree of decomposition of SOM. This indicates that the PAH distribution may be linked to the formation and transformation of fractions: (i) PAHs in the fPOM correspond to relatively recent deposits and mainly reflect the background contamination, (ii) in the oPOM are the PAHs that resist biodegradation during the transformation of fPOM into oPOM and accumulate in the oPOM; this accumulation may be further enhanced by the formation of aggregates. Finally, (iii) in the MaOM, the lower PAH contents can be explained by the different formation pathway of this fraction and its high degree of decomposition. As the PAH distribution may have an impact on their dynamics in soils, it should be taken into consideration in future research.
Auteurs, date et publication :
Auteurs Lise Marchal , Noelia Garcia-Franco , David Gateuille , Luis Carlos Colocho Hurtarte , Christopher Just , Emmanuel Naffrechoux , Martin Wiesmeier , Jérôme Poulenard
Publication : European Journal of Soil Science
Date : 2026
Volume : 76
Issue : 1
Pages : e70059
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Ranunculus glacialis leaves were tested for their plastid terminal oxidase (PTOX) content and electron flow to photorespiration and to alternative acceptors. In shade-leaves, the PTOX and NAD(P)H dehydrogenase (NDH) content were markedly lower than in sun-leaves. Carbon assimilation/ light and Ci response curves were not different in sun- and shade-leaves, but photosynthetic capacity was the highest in sun-leaves. Based on calculation of the apparent specificity factor of ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco), the magnitude of alternative electron flow unrelated to carboxylation and oxygenation of Rubisco correlated to the PTOX content in sun-, shade- and growth chamberleaves. Similarly, fluorescence induction kinetics indicated more complete and more rapid reoxidation of the plastoquinone (PQ) pool in sun- than in shade-leaves. Blocking electron flow to assimilation, photorespiration and the Mehler reaction with appropriate inhibitors showed that sun-leaves were able to maintain higher electron flow and PQ oxidation. The results suggest that PTOX can act as a safety valve in R. glacialis leaves under conditions where incident photon flux density (PFD) exceeds the growth PFD and under conditions where the plastoquinone pool is highly reduced. Such conditions can occur frequently in alpine climates due to rapid light and temperature changes.
Auteurs, date et publication :
Auteurs Constance Laureau , Rosine De Paepe , Gwendal Latouche , Maria Moreno-Chacón , Giovanni Finazzi , Marcel Kuntz , Gabriel Cornic , Peter Streb
Publication : Plant, Cell & Environment
Date : 2025
Volume : 36
Issue : 7
Pages : 1296-1310