Résumé
Atmospheric dioxygen (O2) concentration and isotopic composition are closely linked to the carbon cycle through anthropic carbon dioxide (CO2) emissions and biological processes such as photosynthesis and respiration. The measurement of the isotopic ratio of O2, trapped in ice core bubbles, brings information about past variation in the hydrological cycle at low latitudes, as well as past productivity. Currently, the interpretation of those variations could be drastically improved with a better (i.e., quantitative) knowledge of the oxygen isotopic fractionation that occurs during photosynthesis and respiration processes. This could be achieved, for example, during experiments using closed biological chambers. In order to estimate the isotopic fractionation coefficient with good precision, one of the principal limitations is the need for high-frequency online measurements of isotopic composition of O2, expressed as δ18O of O2 (δ18O(O2)) and O2 concentration. To address this issue, we developed a new instrument, based on the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, enabling high-temporal-resolution and continuous measurements of O2 concentration as well as δ18O(O2), both simultaneously. The minimum Allan deviation occurred between 10 and 20 min, while precision reached 0.002 % for the O2 concentration and 0.06 ‰ for δ18O(O2), which correspond to the optimal integration time and analytical precision before instrumental drift started degrading the measurements. Instrument accuracy was in good agreement with dual-inlet isotope ratio mass spectrometry (IRMS). Measured values were slightly affected by humidity, and we decided to measure δ18O(O2) and O2 concentration after drying the gas. On the other hand, a 1 % increase in O2 concentration increased the δ18O(O2) by 0.53 ‰. To ensure the good quality of O2 concentration and δ18O(O2) measurements we eventually proposed to measure the calibration standard every 20 min.
Auteurs, date et publication :
Auteurs Clément Piel , Daniele Romanini , Morgane Farradèche , Justin Chaillot , Clémence Paul , Nicolas Bienville , Thomas Lauwers , Joana Sauze , Kévin Jaulin , Frédéric Prié , Amaëlle Landais
Publication : Atmospheric Measurement Techniques
Date : 2024
Volume : 17
Issue : 22
Pages : 6647-6658
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Global warming is changing plant communities due to the arrival of new species from warmer regions and declining abundance of cold-adapted species. However, experimentally testing predictions about trajectories and rates of community change is challenging because we normally lack an expectation for future community composition, and most warming experiments fail to incorporate colonization by novel species. To address these issues, we analyzed data from 44 whole-community transplant experiments along 22 elevational gradients across the Northern Hemisphere. In these experiments, high-elevation communities were transplanted to lower elevations to simulate warming, while also removing dispersal barriers for lower-elevation species to establish. We quantified the extent and pace at which warmed high-elevation communities shifted towards the taxonomic composition of lower elevation communities. High-elevation plant communities converged towards the composition of low-elevation communities, with higher rates under stronger experimental warming. Strong community shifts occurred in the first year after transplantation then slowed over time, such that communities remained distinct from both origin and destination control by the end of the experimental periods (3-9 years). Changes were driven to a similar extent by both new species colonization and abundance shifts of high-elevation species, but with substantial variation across experiments that could be partly explained by the magnitude and duration of experimental warming, plot size and functional traits. Our macroecological approach reveals that while warmed high-elevation communities increasingly resemble communities at lower elevations today, the slow pace of taxonomic shifts implies considerable colonization and extinction lags, where a novel taxonomic composition of both low- and high-elevation species could coexist for long periods of time. The important contribution of the colonizing species to community change also indicates that once dispersal barriers are overcome, warmed high-elevation communities are vulnerable to encroachment from lower elevation species.
Auteurs, date et publication :
Auteurs Billur Bektaş , Chelsea Chisholm , Dagmar Egelkraut , Joshua Lynn , Sebastián Block , Thomas Deola , Fanny Dommanget , Brian J. Enquist , Deborah E. Goldberg , Sylvia Haider , Aud H. Halbritter , Yongtao He , Renaud Jaunatre , Anke Jentsch , Kari Klanderud , Paul Kardol , Susanne Lachmuth , Gregory Loucougaray , Tamara Münkemüller , Georg Niedrist
Publication : Ecography
Date : 1970
Volume : n/a
Issue : n/a
Pages : e07378
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Erik H Poelman , Marcel Dicke
Publication : Journal of Herpetology
Date : 2025
Volume : 42
Issue : 2
Pages : 270-278
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Margaret R Metz , Liza S Comita , Yu-Yun Chen , Natalia Norden , Richard Condit , Stephen P Hubbell , I-Fang Sun , Nur Supardi bin Md Noor , S Joseph Wright
Publication : Journal of Tropical Ecology
Date : 2025
Volume : 24
Issue : 1
Pages : 9
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Patrick A Jansen , Peter J Van der Meer , Frans Bongers
Publication : Ecology
Date : 2025
Volume : 89
Issue : 12
Pages : 3490-3502
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs S Pouvelle , F Feer , JF Ponge
Publication : Pedosphere
Date : 2025
Volume : 18
Pages : 691-698
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Sandrine Pouvelle , Sylvie Jouard , François Feer , Thomas Tully , Jean-François Ponge
Publication : Journal of Tropical Ecology
Date : 2025
Volume : 25
Issue : 3
Pages : 239
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Sarah Groc , Jerome Orivel , Alain Dejean , JEAN‐MICHEL MARTIN , MARIE‐PIERRE ETIENNE , Bruno Corbara , Jacques HC Delabie
Publication : Insect Conservation and Diversity
Date : 2025
Volume : 2
Issue : 3
Pages : 183-193
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Brice P Noonan , Aaron A Comeault
Publication : Biology Letters
Date : 2025
Volume : 5
Issue : 1
Pages : 51-54
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Max Ringler , Eva Ursprung , Walter Hödl
Publication : Behavioral Ecology and Sociobiology
Date : 2025
Volume : 63
Issue : 9
Pages : 1281-1293