Résumé
Leaf mass per area (LMA) is an important leaf trait but challenging to be accurately estimated. This article proposes a simple leaf radiative transfer model called ISPECT. It explains the difference in optical properties observed on the adaxial (upper) and abaxial (lower) sides of leaves, i.e., their dorsiventrality, with a limited number of structural parameters. The performance of ISPECT in estimating LMA is compared to that of five other leaf radiative transfer models (FASPECT, DLM, PROSPECT-D, PROSPECT-5B, and Leaf-SIP). We tested six experimental datasets with 962 leaf samples and two spectral ranges: the solar domain (0.4–2.5 μm) and the shortwave infrared (1.7–2.4 μm). Results show that PROSPECT-D and PROSPECT-5B accurately estimate LMA using the shortwave infrared spectra, while ISPECT and FASPECT perform well in both spectral ranges. Further analysis demonstrates that leaf dorsiventrality is likely to be an influential factor for LMA estimation: thus ISPECT can accurately estimate LMA in the solar and shortwave infrared domains, with NRMSE of 26.0% and 28.8%, respectively. This motivates further studies on LMA mapping from spaceborne imaging spectrometers (e.g., PRISMA, GaoFen-5, EnMAP) by coupling ISPECT with canopy radiative transfer models.
Auteurs, date et publication :
Auteurs Hanyu Shi , Jingyi Jiang , Stéphane Jacquemoud , Zhiqiang Xiao , Mingguo Ma
Publication : Remote Sensing of Environment
Date : 2025
Volume : 286
Pages : 113444
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Intraspecific variability (IV) has been proposed to explain species coexistence in diverse communities. Assuming, sometimes implicitly, that conspecific individuals can perform differently in the same environment and that IV increases niche overlap, previous studies have found contrasting results regarding the effect of IV on species coexistence. We aim at showing that the large IV observed in data does not mean that conspecific individuals are necessarily different in their response to the environment and that the role of high-dimensional environmental variation in determining IV has largely remained unexplored in forest plant communities. We first used a simulation experiment where an individual attribute is derived from a high-dimensional model, representing “perfect knowledge” of individual response to the environment, to illustrate how large observed IV can result from “imperfect knowledge” of the environment. Second, using growth data from clonal Eucalyptus plantations in Brazil, we estimated a major contribution of the environment in determining individual growth. Third, using tree growth data from long-term tropical forest inventories in French Guiana, Panama and India, we showed that tree growth in tropical forests is structured spatially and that despite a large observed IV at the population level, conspecific individuals perform more similarly locally than compared with heterospecific individuals. As the number of environmental dimensions that are well quantified at fine scale is generally lower than the actual number of dimensions influencing individual attributes, a great part of observed IV might be represented as random variation across individuals when in fact it is environmentally driven. This mis-representation has important consequences for inference about community dynamics. We emphasize that observed IV does not necessarily impact species coexistence per se but can reveal species response to high-dimensional environment, which is consistent with niche theory and the observation of the many differences between species in nature.
Auteurs, date et publication :
Auteurs Camille Girard‐Tercieux , Isabelle Maréchaux , Adam T. Clark , James S. Clark , Benoît Courbaud , Claire Fortunel , Joannès Guillemot , Georges Künstler , Guerric Le Maire , Raphaël Pélissier , Nadja Rüger , Ghislain Vieilledent
Publication : Ecology and Evolution
Date : 2025
Volume : 13
Issue : 3
Pages : e9860
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Subalpine grasslands support biodiversity, agriculture, and tourism but their resilience to extreme climatic events is challenged accelerating their vulnerability to tipping points. Microbial communities, central in ecosystem functioning, are usually considered more resistant and highly resilient to extreme events albeit their functional redundancy and strong selection by local harsh climatic conditions. This study explored the soil microbial responses upon recurrent spring‐summer droughts associated with early snowmelt in subalpine grasslands mesocosms set‐up at the Lautaret Pass (French Alps). Potential soil microbial respiration, nitrification and denitrification activities were monitored over a period of two growing seasons along with quantification of related gene abundances. Impacts of simulated spring‐summer drought and early snowmelt were quantified to assess their resistance and recovery. Results revealed that droughts had a low and short‐term adverse impact on bacterial total respiration supporting their hypothesized high resilience, i.e. resistance and ability to recover. Nitrification and abundances of the corresponding functional guilds showed relatively strong resistance to summer droughts but declined in response to early snowmelt. This resistance of nitrification was paralleled by the recovery of denitrification and abundances of denitrifying communities from all climatic extremes, except from the summer droughts where nitrifiers were collapsed. Denitrification and respective functional groups faced high impact of applied stresses with strong reduction in abundance and activity. Although, consequently lower denitrifiers' competition for nitrate may be positive for plant biomass production, warnings exist when considering the potential nitrate leaching as well as risks of greenhouses gases emission such as N
2
O from these ecosystems.
Auteurs, date et publication :
Auteurs Farhan Hafeez , Jean‐Christophe Clément , Lionel Bernard , Franck Poly , Thomas Pommier
Publication : Oikos
Date : 2025
Volume : 2023
Issue : 7
Pages : e09836
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Cyberinfrastructure is a product of the information age that provides a framework for informing adaptive management of ecological entities under the impact of regional and global change. It supports proximity monitoring, user-friendly data management, knowledge discovery by data synthesis, and decision making by forecasting.
Auteurs, date et publication :
Auteurs Friedrich Recknagel
Publication : Ecological Informatics
Date : 2025
Volume : 75
Pages : 102039
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Few high-resolution paleoclimate proxy records exist in the region located under the direct influence of the Intertropical Convergence Zone (ITCZ) in South America and most of them were retrieved from the Cariaco Basin off the coast of Venezuela. Here we present new ẟ18O and ẟ13C records of Venezuelan speleothems collected in caves adjacent to Cariaco, covering the mid- and late-Holocene. We document previously undetected secular-to multidecadal-scale climate variability in the core region of the ITCZ, which is compared to other high-resolution records from the North Atlantic, Caribbean and tropical South America. Over the mid-Holocene our record exhibits broad swings between periods of reduced (8.3e8.0, 6.5e5.0, 4.1e3.6 ka BP) and increased (8.5, 8.0e6.5, 4.9e4.2 ka BP) rainfall. In particular, between 5.5 and 5.0 ka BP, increases in polar and subpolar North Atlantic ice rafted debris and a reduction in North Atlantic Deep Water (NADW) formation might have contributed to the southward displacement of the North Atlantic Subtropical High (NASH) and the ITCZ, which led to severe dry conditions in north central Venezuela and an enhancement of the South American Monsoon System (SAMS). During the lateHolocene, contrary to data from Cariaco reported in previous studies, our results point to drier conditions during the Medieval Climate Anomaly (MCA, 900e1100 CE), which were further amplified during positive Atlantic Multidecadal Oscillation (AMO) phases. Wet conditions, however, prevailed during the first part of the Little Ice Age (LIA, 1400e1500 CE). No speleothem deposition occurred during the main LIA period, which might be related to drier conditions in response to a southward displacement of the ITCZ that led to major moisture convergence over the SASM domain. Our new records from Venezuela provide a reliable proxy for ITCZ behavior over the Atlantic e South America domain and document past dynamics in relation to other climate systems (NASH and SAMS), while providing new evidence of ITCZ e North Atlantic teleconnections during the Holocene.
Auteurs, date et publication :
Auteurs N. Melissa M. Medina , Francisco W. Cruz , Amos Winter , Haiwei Zhang , Angela Ampuero , Mathias Vuille , Víctor C. Mayta , Marília C. Campos , Verónica Marcela Rámirez , Giselle Utida , Andrés Camilo Zúñiga , Hai Cheng
Publication : Quaternary Science Reviews
Date : 2025
Volume : 307
Pages : 108056
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Jonathan Donhauser , Maria J.I. Briones , Juha Mikola , Davey L. Jones , Reinhard Eder , Juliane Filser , Aline Frossard , Paul Henning Krogh , José Paulo Sousa , Jérome Cortet , Ellen Desie , Xavier Domene , Simoneda Djuric , Davorka Hackenberger , Juan J. Jimenez , Maria Iamandei , Cornelia Rissmann , Olaf Schmidt , Merrit Shanskiy , Tarja Silfver
Publication : Soil Biology and Biochemistry
Date : 2025
Volume : 185
Pages : 109154
Catégorie(s)
#CNRSRésumé
This study reviews the Ficus americana species complex, a group mostly distributed throughout South America. Following the taxonomic analysis of approximately 60 names related to the group, we specify the new Kinuppii series of 9 species, a ramiflorous group which is delimited by the presence of spurs in the branches, a unique characteristic of the new taxon of Neotropical Ficus. Ficus longifolia and F. schippii are included in the new series, but have not previously been cited as part of the F. americana species complex. Ficus clusiifolia, F. fresnoensis, F. guianensis, F. mathewsii, and F. subapiculata are treated as accepted species names and no longer considered varieties of F. americana. Completing the new series are F. albert-smithii and F. sphenophylla. Epitypes were designated for F. clusiifolia and F. longifolia and a neotype for F. herthae. In this study, F. leiophylla is considered a synonym of F. mathewsii as the leaf shape varies considerably within the taxon. Synonyms, analysis of protologues, types, descriptions, taxonomic key, examined materials, and maps complete the analysis.
Auteurs, date et publication :
Auteurs Leandro C. Pederneiras , Henrique B. Zamengo , Angelo Danilo Plata-Castro , Sergio Romaniuc-Neto , Vidal De F. Mansano
Publication : Brittonia
Date : 2025
Volume : 75
Issue : 3
Pages : 249-268
Catégorie(s)
#CNRS #FORET NouraguesRésumé
A new monotypic genus in the ‘Archeuptychia clade’ Xikrin Barbosa, Freitas, Siewert & Marín gen. nov. (Nymphalidae: Satyrinae: Euptychiina) is described to accommodate a new species, Xikrin ueharapradoi Freitas & Barbosa gen. et sp. nov., in the highly diverse Satyrinae subtribe Euptychiina, based mainly on molecular data. To date, this species is known only from the region of Carajas, in the eastern Amazon rainforest. The phylogenetic relationship and taxonomy of this new taxon are discussed.
Auteurs, date et publication :
Auteurs Eduardo P. Barbosa , Ricardo R. Siewert , Mario A. Marín , Patrícia A. Machado , Isabela F. Oliveira , José A. C. Filho , André V. L. Freitas
Publication : Austral Entomology
Date : 2025
Volume : 62
Issue : 3
Pages : 310-322
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Abstract
Biogeochemical niche (BN) hypothesis aims to relate species/genotype elemental composition with its niche based on the fact that different elements are involved differentially in distinct plant functions. We here test the BN hypothesis through the analysis of the 10 foliar elemental concentrations and 20 functional‐morphological of 60 tree species in a French Guiana tropical forest. We observed strong legacy (phylogenic + species) signals in the species‐specific foliar elemental composition (elementome) and, for the first time, provide empirical evidence for a relationship between species‐specific foliar elementome and functional traits. Our study thus supports the BN hypothesis and confirms the general niche segregation process through which the species‐specific use of bio‐elements drives the high levels of α‐diversity in this tropical forest. We show that the simple analysis of foliar elementomes may be used to test for BNs of co‐occurring species in highly diverse ecosystems, such as tropical rainforests. Although cause and effect mechanisms of leaf functional and morphological traits in species‐specific use of bio‐elements require confirmation, we posit the hypothesis that divergences in functional‐morphological niches and species‐specific biogeochemical use are likely to have co‐evolved.
Auteurs, date et publication :
Auteurs Jordi Sardans , Joan Llusià , Romà Ogaya , Helen Vallicrosa , Iolanda Filella , Albert Gargallo‐Garriga , Guille Peguero , Leandro Van Langenhove , Lore T. Verryckt , Clément Stahl , Elodie A. Courtois , Laëtitia M. Bréchet , Akash Tariq , Fanjiang Zeng , Abdulwahed Fahad Alrefaei , Weiqi Wang , Ivan A. Janssens , Josep Peñuelas
Publication : Ecology
Date : 2025
Volume : 104
Issue : 11
Pages : e4118
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
The detection of solar induced chlorophyll fluorescence (SIF) in the field with spectrometers is based on the depth of the solar Fraunhofer or oxygen absorption lines in the upwelling radiance compared to that in the downwelling irradiance. This relative depth enables the differentiation of SIF from the reflected radiation. Recent studies have shown that if oxygen bands are used to retrieve SIF from tower-based measurements, then atmospheric correction is required. This study presents a band shape fitting (BSF) approach to retrieve both the relative optical path length (deepening) and SIF (infilling) from field measurements at the same time, using information in the measured spectral shape of the O2 feature. This approach is an alternative to using radiative transfer process models for estimating atmospheric transmittance. The method was applied to measurements taken from 100 m elevation above a forest, yielding plausible results for SIF in the O2A and O2B bands. The sensitivity to combined atmospheric and instrument characteristics prohibits application at much greater distances from the surface.
Auteurs, date et publication :
Auteurs Christiaan van der Tol , Tommaso Julitta , Peiqi Yang , Neus Sabater , Ilja Reiter , Marin Tudoroiu , Dirk Schuettemeyer , Matthias Drusch
Publication : Remote Sensing of Environment
Date : 2023
Volume : 284
Pages : 113304