Résumé
Hydraulic modelling is a primary tool to predict plant performance in future drier scenarios. However, as most tree models are validated under non-stress conditions, they may fail when water becomes limiting. To simulate tree hydraulic functioning under moist and dry conditions, the current version of a water flow and storage mechanistic model was further developed by implementing equations that describe variation in xylem hydraulic resistance (RX) and stem hydraulic capacitance (CS) with predawn water potential (Ψ PD). The model was applied in a Mediterranean forest experiencing intense summer drought, where six Quercus ilex trees were instrumented to monitor stem diameter variations and sap flow, concurrently with measurements of predawn and midday leaf water potential. Best model performance was observed when CS was allowed to decrease with decreasing Ψ PD. Hydraulic capacitance decreased from 62 to 25 kg mÀ3 MPaÀ1 across the growing season. In parallel, tree transpiration decreased to a greater extent than the capacitive water release and the contribution of stored water to transpiration increased from 2.0 to 5.1%. Our results demonstrate the importance of stored water and seasonality in CS for tree hydraulic functioning, and they suggest that CS should be considered to predict the drought response of trees with models.
Auteurs, date et publication :
Auteurs Roberto L Salomón , Jean-Marc Limousin , Jean-Marc Ourcival , Jesús Rodríguez-Calcerrada , Kathy Steppe
Publication : Plant, Cell & Environment
Date : 2025
Volume : 40
Issue : 8
Pages : 1379-1391
Catégorie(s)
#CNRS #FORET PuechabonRésumé
Cuticular hydrocarbons (CHCs) are ubiquitous and highly diverse in insects, serving as communication signal and waterproofing agent. Despite their vital function, the causes, mechanisms and constraints on CHC diversification are still poorly understood. Here, we investigated phylogenetic constraints on the evolution of CHC profiles, using a global data set of the species-rich and chemically diverse ant genus Crematogaster. We decomposed CHC profiles into quantitative (relative abundances, chain length) and qualitative traits (presence/absence of CHC classes). A species-level phylogeny was estimated using newly generated and previously published sequences from five nuclear markers. Moreover, we reconstructed a phylogeny for the chemically diverse Crematogaster levior species group using cytochrome oxidase I. Phylogenetic signal was measured for these traits on genus and clade level and within the chemically diverse C. levior group. For most quantitative CHC traits, phylogenetic signal was low and did not differ from random expectation. This was true on the level of genus, clade and species group, indicating that CHC traits are evolutionary labile. In contrast, the presence or absence of alkenes and alkadienes was highly conserved within the C. levior group. Hence, the presence or absence of biosynthetic pathways may be phylogenetically constrained, especially at lower taxonomic levels. Our study shows that CHC composition can evolve rapidly, allowing insects to quickly adapt their chemical profiles to external selection pressures, whereas the presence of biosynthetic pathways appears more constrained. However, our results stress the importance to consider the taxonomic level when investigating phylogenetic constraints.
Auteurs, date et publication :
Auteurs F. Menzel , T. Schmitt , B. B. Blaimer
Publication : Journal of Evolutionary Biology
Date : 2025
Volume : 30
Issue : 7
Pages : 1372-1385
Catégorie(s)
#CNRS #FORET NouraguesRésumé
1. Estimating forest above-ground biomass (AGB), or carbon (AGC), in tropical forests has become a major concern for scientists and stakeholders. However, AGB assessment procedures are not fully standardized and even more importantly, the uncertainty associated with AGB estimates is seldom assessed.
Auteurs, date et publication :
Auteurs Maxime Réjou-Méchain , Ariane Tanguy , Camille Piponiot , Jérôme Chave , Bruno Hérault , Sarah Goslee
Publication : Methods in Ecology and Evolution
Date : 2025
Volume : 8
Issue : 9
Pages : 1163-1167
Catégorie(s)
#CNRS #FORET NouraguesRésumé
In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research.
Auteurs, date et publication :
Auteurs Wolfgang W. Weisser , Christiane Roscher , Sebastian T. Meyer , Anne Ebeling , Guangjuan Luo , Eric Allan , Holger Beßler , Romain L. Barnard , Nina Buchmann , François Buscot , Christof Engels , Christine Fischer , Markus Fischer , Arthur Gessler , Gerd Gleixner , Stefan Halle , Anke Hildebrandt , Helmut Hillebrand , Hans de Kroon , Markus Lange
Publication : Basic and Applied Ecology
Date : 2025
Volume : 23
Pages : 1-73
Catégorie(s)
#CNRS #Ecotron de MontpellierAuteurs, date et publication :
Auteurs Alexandru Milcu , Arthur Gessler , Christiane Roscher , Laura Rose , Zachary Kayler , Dörte Bachmann , Karin Pirhofer-Walzl , Saša Zavadlav , Lucia Galiano , Tina Buchmann , Michael Scherer-Lorenzen , Jacques Roy
Publication : Scientific Reports
Date : 2025
Volume : 7
Issue : 1
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
We present a multidisciplinary approach to document the vegetation and landscape of Upper Guisane Valley around the Lautaret Pass area in the French Southwestern Alps since 7200 calyr BP. We combined pollen analysis in a peat bog (at 2044 m) with a leaf imprint study in two nearby travertine systems (at 2100 and 1950 m). During the last 7200 years, there was an open landscape with scarce trees such asconifers including Larix decidua Mill., Pinus spp., and Abies alba Mill. 2100 m was the highest altitude where fossils of A. alba Mill. have been reported in the Guisane Valley. These results, according to the pollen record of anthropogenic indicators and an increasing biodiversity of grasslands, suggest a human presence in the pass area since ca 6500 years with a preRoman deforestation. This human impact has become maximum from 1100 calyr BP to present, resulting from cereal crop agriculture and deforestation. The comparative study of the different records confirmed the role played by the exposition in the forest dynamics of the alpine valleys during the Holocene.
Auteurs, date et publication :
Auteurs Anne-Lise Cabanat , Fernand David , Jean-Louis Latil , Christophe Perrier , Serge Aubert
Publication : Review of Palaeobotany and Palynology
Date : 2025
Volume : 246
Pages : 32-43
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Nick M. Haddad , Robert D. Holt , Robert J., Jr. Fletcher , Michel Loreau , Jean Clobert
Publication : ECOGRAPHY
Date : 2017
Volume : 40
Issue : 1
Pages : 1-8
Catégorie(s)
#ANR-Citation #CNRS #Metatron terrestreRésumé
Earlier snowmelt changes spring stress exposure and growing-season length, possibly causing shifts in plant species dominance. If such shifts involve trees, this may lead to changes in treeline position. We hypothesized that earlier snowmelt would negatively affect the performance of tree seedlings near the treeline due to higher spring stress levels, but less so if seedlings were protected from the main stress factors of night frosts and excess solar radiation. We exposed seedlings of five European treeline tree species: Larix decidua, Picea abies, Pinus cembra, Pinus uncinata, and Sorbus aucuparia to two snow-cover treatments (early and late melting, with about two weeks difference) combined with reduced sky exposure during the day (shading) or night (night warming), repeated in two years, at a site about 200 m below the regional treeline elevation. Physiological stress levels (as indicated by lower Fv/Fm) in the first weeks after emergence from snow were higher in early-emerging seedlings. As expected, shade reduced stress, but contrary to expectation, night warming did not. However, early- and late-emerging seedlings did not differ overall in their growth or survival, and the interaction with shading was inconsistent between years. Overall, shading had the strongest effect, decreasing stress levels and mortality (in the early-emerging seedlings only), but also growth. A two-week difference in snow-cover duration did not strongly affect the seedlings, although even smaller differences have been shown to affect productivity in alpine and arctic tundra vegetation. Still, snowmelt timing cannot be discarded as important for regeneration in subalpine conditions, because (1) it is likely more critical in very snow-rich or snow-poor mountains or landscape positions; and (2) it can change (sub)alpine vegetation phenology and productivity, thereby affecting plant interactions, an aspect that should be considered in future studies.
Auteurs, date et publication :
Auteurs Maaike Y. Bader , Hannah Loranger , Gerhard Zotz , Glenda Mendieta-Leiva
Publication : Forests
Date : 2025
Volume : 9
Issue : 1
Pages : 12
Catégorie(s)
#CNRS #Lautaret #UGARésumé
INTRODUCTION: Clear cell renal cell carcinomas (ccRCCs) are highly metastatic tumors with metastases detected at diagnosis (synchronous) or during follow-up (metachronous). To date, there have been no reports comparing primary ccRCC of patients with synchronous and metachronous metastases, who are different in terms of prognosis. Determining whether there is a phenotypic difference between these 2 groups could have important clinical implications.
PATIENTS AND METHODS: In a retrospective consecutive cohort of 98 patients with ccRCC, 48 patients had metastases, including 28 synchronous and 20 metachronous presentations, with a follow-up of 10 years. For each primary tumor in these metastatic patients, pathologic criteria, expression of vascular endothelial growth factor, partitioning-defective 3, CAIX, and programmed death ligand 1 as detected by immunohistochemistry, and complete VHL status were analyzed. Univariate analysis was performed, and survival was assessed using Kaplan-Meier curves compared by log-rank test.
RESULTS: Compared with primary ccRCC in patients with metachronous metastases, primary ccRCC in patients with synchronous metastases were significantly associated with a poorer Eastern Cooperative Oncology Group performance (P = .045), higher pT status (P = .038), non-inactivated VHL gene (P = .01), sarcomatoid component (P = .007), expression of partitioning-defective 3 (P = .007), and overexpressions of vascular endothelial growth factor (> 50%) (P = .017) and programmed death ligand 1 (P = .019). Patients with synchronous metastases had a worse cancer-specific survival than patients with metachronous metastases even from metastatic diagnosis (median survival, 16 months vs. 46 months, respectively; P = .01).
CONCLUSION: This long-term study is the first to support the notion that synchronous m-ccRCC has a distinct phenotype. This is probably linked to the occurrence of oncogenic events that could explain the worse prognosis. These particular patients with metastases could benefit from specific therapy.
Auteurs, date et publication :
Auteurs Solene-Florence Kammerer-Jacquet , Angelique Brunot , Adelaide Pladys , Guillaume Bouzille , Julien Dagher , Sarah Medane , Benoit Peyronnet , Romain Mathieu , Gregory Verhoest , Karim Bensalah , Julien Edeline , Brigitte Laguerre , Alexandra Lespagnol , Jean Mosser , Frederic Dugay , Marc-Antoine Belaud-Rotureau , Nathalie Rioux-Leclercq
Publication : Clinical Genitourinary Cancer
Date : 2017
Volume : 15
Issue : 1
Pages : e1-e7
Catégorie(s)
#CNRS #EcoGenO #Université de RennesAuteurs, date et publication :
Auteurs Talie Musavi , Mirco Migliavacca , Markus Reichstein , Jens Kattge , Christian Wirth , T. Andrew Black , Ivan Janssens , Alexander Knohl , Denis Loustau , Olivier Roupsard , Andrej Varlagin , Serge Rambal , Alessandro Cescatti , Damiano Gianelle , Hiroaki Kondo , Rijan Tamrakar , Miguel D. Mahecha
Publication : Nature Ecology & Evolution
Date : 2017
Volume : 1
Issue : 2
Pages : 0048