Résumé
Increasing drought caused by the ongoing climate change, and forest management by thinning that aims at mitigating its impact, may modify the current relationships between forest functions and drought intensity and preclude our ability to forecast future ecosystem responses.
Auteurs, date et publication :
Auteurs Jordane Gavinet , Jean‐Marc Ourcival , Jean‐Marc Limousin
Publication : New Phytologist
Date : 2025
Volume : 223
Issue : 3
Pages : 1267-1279
Catégorie(s)
#CNRS #FORET PuechabonRésumé
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 #UGAAuteurs, date et publication :
Auteurs Bill Shipley , CE Timothy Paine , Christopher Baraloto
Publication : Ecology
Date : 2025
Volume : 93
Issue : 4
Pages : 760-769
Catégorie(s)
#CNRS #FORET NouraguesRésumé
It is necessary to increase our understanding of the influence of climate and biological drivers on the interannual variations in carbon (C) exchange between forests and the atmosphere. To this aim, a processbased model (CASTANEA) was used for simulating C exchanges over four European forests, encompassing a broad latitudinal gradient (from Mediterranean to boreal climate zones), for the years 2000–2007. CASTANEA reproduced 74–95% of the daily and 35–84% of the annual variance in daytime net ecosystem productivity (NEP). Constrained simulations allowed us to isolate the individual contributions of climatic drivers (radiation, temperature and relative humidity), hydrological drivers (soil water) and biological drivers (canopy dynamics, the thermal acclimation of photosynthetic capacities in evergreens, and vegetative and microbial C pools) to the anomalies in C exchange for timescales ranging from daily to annual. Orthonormal wavelet transformation of these single-contribution time series allowed us to quantify the individual drivers’ influences on flux variance across time scales. High frequency departures from mean annual C exchange patterns were mostly caused by hydroclimate modulations (87–99% of the flux variance from daily to weekly scales). The integration of these anomalies at the annual scale yielded a higher contribution of biological drivers: we identified a primary controller of gross primary production (GPP) variations through modulations of soil water in both the Mediterranean Quercus ilex and the temperate Fagus sylvatica forests; we also identified at the annual scale a complex determinism for both coniferous sites, with an unexpectedly higher contribution of the thermal acclimation driver at the temperate (warmer) site. Although all but one site experienced structural perturbations during the study period, interannual variations in ecosystem respiration (Reco) were readily related to changes in temperature and soil water, with a low contribution from variations in C pools at the annual scale. As a result of the preponderant dependence of net ecosystem production (NEP) on GPP fluxes, the inferred determinism of simulated net exchanges appeared similar to that of GPP. However, compensations occurred, leading, for example, to a much lower influence of soil water modulations on NEP than on GPP or Reco at the Mediterranean site.
Auteurs, date et publication :
Auteurs N Delpierre
Publication : Agricultural and Forest Meteorology
Date : 2025
Pages : 14
Catégorie(s)
#CNRS #FORET PuechabonAuteurs, 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
Species dispersal and resource spatial flows greatly affect the dynamics of connected ecosystems. So far, research on meta-ecosystems has mainly focused on the quantitative effect of subsidy flows. Yet, resource exchanges at heterotrophic-autotrophic (e.g., aquatic-terrestrial) ecotones display a stoichiometric asymmetry that likely matters for functioning. Here, we joined ecological stoichiometry and the meta-ecosystem framework to understand how subsidy stoichiometry mediates the response of the meta-ecosystem to subsidy flows. Our model results demonstrate that resource flows between ecosystems can induce a positive spatial feedback loop, leading to higher production at the meta-ecosystem scale by relaxing local ecosystem limitations (“spatial complementarity”). Furthermore, we show that spatial flows can also have an unexpected negative impact on production when accentuating the stoichiometric mismatch between local resources and basal species needs. This study paves the way for studies on the interdependancy of ecosystems at the landscape extent.
Data: The code and the data, as well as a small tutorial to run the model are available on Github via Zenodo: https://doi.org/10.5281/zenodo.7733880
Auteurs, date et publication :
Auteurs Benôıt Pichon , Elisa Thébault , Gérard Lacroix , Isabelle Gounand
Date : 2023
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
When assessing the carbon storage potential of a crop, it is useful to 1) quantify the inputs that return to the soil, such as roots, rhizodeposition and sometimes aboveground biomass, and 2) estimate the carbon gains or losses attributed to the priming effect. This allows to draw up a balance of inputs and outputs at the end of the growing season. While the quantity of carbon supplied by roots and aboveground biomass is relatively easy to measure, the quantity of rhizodeposition and the priming effect are not.To establish such a balance, 12 intercropping plant species from 3 plant families (brassicaceae, fabaceae and poaceae) were grown for two months in mesocosms (15 liters) under controlled conditions simulating a temperate summer climate in real time in an ecotron. Multi-pulse atmospheric labeling with 13CO2 99% was used to trace photosynthesized carbon and thus quantify aboveground and root biomass, rhizodeposition and variations in carbon stock due to the priming effect.The results show that rhizodeposition represents a significant carbon input (around a quarter of root biomass), positively correlated with root biomass. Root biomass is therefore one of the main traits to be considered for increasing inputs. At the same time, 10 out of 12 plants accelerated the mineralization of soil organic matter (positive priming effect), resulting in a cumulative carbon loss over the course of the plant's growth that can be of the same order of magnitude as the biomass input.This priming effect is highly heterogeneous and difficult to explain by plant traits, but seems quantitatively more important for brassicaceae. We propose that this variability is due both to the spatial heterogeneity inducing these processes, but also to the great variability of processes that can occur in the rhizosphere, processes that can simultaneously lead to an acceleration and/or deceleration of the decomposition of native soil organic matter.
Auteurs, date et publication :
Auteurs Baptiste Hulin , Simon Chollet , Folrent Massol , Samuel Abiven
Date : 2024
Pages : 5143
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENSRésumé
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
Key message We combined aerial LiDAR and ground sensors to map the spatial variation in micro-environmental variables of the tropical forest understory. We show that these metrics depend on forest type and proximity to canopy gaps. Our study has implications for the study of natural forest regeneration.
Auteurs, date et publication :
Auteurs Blaise Tymen , Grégoire Vincent , Elodie A. Courtois , Julien Heurtebize , Jean Dauzat , Isabelle Marechaux , Jérôme Chave
Publication : Annals of Forest Science
Date : 2025
Volume : 74
Issue : 2