Auteurs, date et publication :
Auteurs Alicia Ledo , Keryn I. Paul , David F. R. P. Burslem , John J. Ewel , Craig Barton , Michael Battaglia , Kim Brooksbank , Jennifer Carter , Tron Haakon Eid , Jacqueline R. England , Anthony Fitzgerald , Justin Jonson , Maurizio Mencuccini , Kelvin D. Montagu , Gregorio Montero , Wilson Ancelm Mugasha , Elizabeth Pinkard , Stephen Roxburgh , Casey M. Ryan , Ricardo Ruiz-Peinado
Publication : NEW PHYTOLOGIST
Date : 2018
Volume : 217
Issue : 1
Pages : 8-11
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
The main goal of this paper is to derive a method for a daily gross primary production (GPP) product over Europe and Africa taking the full advantage of the SEVIRI/MSG satellite products from the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) sensors delivered from the Satellite Application Facility for Land Surface Analysis (LSA SAF) system. Special attention is paid to model the daily GPP response from an optimized Montheith's light use efficiency model under dry conditions by controlling water shortage limitations from the actual evapotranspiration and the potential evapotranspiration (PET). The PET was parameterized using the mean daily air temperature at 2m (Ta) from ERA-Interim data. The GPP product (MSG GPP) was produced for 2012 and assessed by direct site-level comparison with GPP from eddy covariance data (EC GPP). MSG GPP presents relative bias errors lower than 40% for the most forest vegetation types with a high agreement (r>0.7) when compared with EC GPP. For drylands, MSG GPP reproduces the seasonal variations related to water limitation in a good agreement with site level GPP estimates (RMSE=2.11gm−2day−1; MBE=−0.63gm−2day−1), especially for the dry season. A consistency analysis against other GPP satellite products (MOD17A2 and FLUXCOM) reveals a high consistency among products (RMSD3.0gm−2day−1) and over dry biomes with MSG GPP estimates lower than FLUXCOM (MBD up to −3.0gm−2day−1). This newly derived product has the potential for analysing spatial patterns and temporal dynamics of GPP at the MSG spatial resolutions on a daily basis allowing to better capture the GPP dynamics and magnitude.
Auteurs, date et publication :
Auteurs B. Martínez , S. Sanchez-Ruiz , M. A. Gilabert , A. Moreno , M. Campos-Taberner , F. J. García-Haro , I. F. Trigo , M. Aurela , C. Brümmer , A. Carrara , A. De Ligne , D. Gianelle , T. Grünwald , J. M. Limousin , A. Lohila , I. Mammarella , M. Sottocornola , R. Steinbrecher , T. Tagesson
Publication : International Journal of Applied Earth Observation and Geoinformation
Date : 2018
Volume : 65
Pages : 124-136
Catégorie(s)
#CNRS #FORET PuechabonRésumé
The "PLAteforme expérimentale Nationale d'écologie
AQUAtique" is a multi-scale experimental infrastructure created in 2011
to make possible the analysis of human disturbance on aquatic
biodiversity, community structure, and ecosystem functioning. It is
funded by the "Investissements d'avenir Equipex" program and is partner
of the ANAEE-France research infrastructure. PLANAQUA provides the
scientific community with access to experimental highly instrumented
platforms available year round through calls for projects open to all
researchers around the world. It includes: 1) Microcosms (1-6 L),
developed for studying plankton ecology and physiology under highly
controlled environmental conditions in the dedicated laboratory or in
the climatic rooms of the Ecotron IleDeFrance. Organisms and ecosystems
activity and dynamics are precisely monitored by a series of dedicated
sensors and instruments. 2) Mesocosms (1-15 m3), have a high degree of
replication. They are installed outdoors and can house complex
communities of organisms. Among them a series of twelve is equipped with
beaters that generate waves, making possible to control the physical
structure of the water column thus to study the link between physical
constraints and functioning of aquatic systems. 3) Macrocosms, sixteen
artificial lakes (650 m3) dedicated to understand the functioning of
complex natural communities with heterogeneous spatial distributions;
they will allow ascertaining the consequences of anthropogenic pressures
on biodiversity, up to the top of the food chains. They are equipped
with automated sensors and data loggers for high-frequency data
collection of the main physical-chemical parameters. PLANAQUA is located
at the CEREEP research center (CNRS-ENS, UMS 3194) near Paris.
Keywords: Aquatic ecosystems functioning and dynamics, plankton
eco-physiology, biodiversity, environmental changes, experimental
platform, multi-scale studies, instruments and sensors
Auteurs, date et publication :
Auteurs Sarah Fiorini , Alexis Millot , Simon Chollet , Florent Massot , Jean-François Le Galliard , Emma Rochelle-Newall , Gerard Lacroix
Date : 2018
Volume : 20
Pages : 9724
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENS #PLANAQUARésumé
Although the impacts of eutrophication on freshwater biodiversity are
relatively well known, how eutrophication impacts the quality of
dissolved organic carbon (DOC) is less known, despite its importance for
microbial nutrition. Chromophoric dissolved organic matter (CDOM) is the
fraction of the bulk DOC pool that absorbs light and shifts in the
absorption and fluorescence of this component indicate an alteration in
the quality of the DOC present. Here we looked at the impact of small
phosphorus additions on CDOM absorption and fluorescence in a series of
16, newly constructed and filled, experimental lakes (Plateforme
Planaqua, UMS CEREEP, France). Eight of the lakes received small
additions (+ 100 µM) of phosphorus during late spring and summer
2015. We show that there was a distinct seasonal pattern to DOC and to
all measured CDOM parameters, regardless of nutrient status. We also
show that despite a lack of significant difference between the lakes in
terms of DOC concentrations, there were striking differences in the
carbon-normalised CDOM parameters. For example, we observed a
significant increase in the carbon normalized absorption at 254 nm
(SUVA254) in the lakes with addition of P, this was also the case for
fluorescence (ex350/em450) normalized to carbon concentration. These
changes were also accompanied by shifts in the relative intensities of
the components in the fluorescence excitation-emission matrices (EEM).
We propose that even small shifts in phosphorus availability can induce
strong shifts in carbon quality and that this may well have
repercussions up the food web should this more aromatic CDOM prove to be
less bioavailable. These results also imply that the brownification
observed in lakes in northern Europe may also be partially due to small
shifts in nutrient concentrations combined with increased carbon and
suspended solids imports from the surrounding catchments.
Auteurs, date et publication :
Auteurs Emma Rochelle-Newall , Lydie Blottière , Colombe Consortium
Date : 2018
Volume : 20
Pages : 9464
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
A trophic radiation in the South-American annual killifish genus Austrolebias has led to the evolution of large specialized piscivores from small generalized carnivores. It has been proposed that this occurred in a single series of vicariant speciation events. An alternative hypothesis is denoted giant-dwarf speciation: piscivores would have evolved in sympatry by character displacement and cannibalism. We test the plausibility of both scenarios using size measures combined with distributional data and new phylogenetic trees based on mitochondrial and nuclear molecular markers. Our analysis uses historical biogeography models and Ornstein-Uehlenbeck processes describing trait evolution across the posterior distributions of phylogenetic trees. Large species most likely evolved three times from small ones. For the clade containing A. elongatus, we argue that vicariance was not involved in the origin of these large and specialized piscivores. They experience stabilizing selection with an optimum shifted towards larger bodies and longer jaws. The branch leading to this clade has the fastest evolving jaw lengths across the phylogeny, in agreement with expectations for giant-dwarf speciation. For A. wolterstorffi, the support for giant-dwarf speciation is weaker. When the species is placed at the root of Austrolebias, ancestral reconstructions are unreliable and vicariance cannot be ruled out. For the remaining large species, we can reject vicariance and giant dwarf speciation. Our results give rise to two new additional scenarios for the evolution of specialized piscivores. In the first, two successive speciation events in sympatry or parapatry produced large and piscivorous species. In the second, the immigration of a different annual killifish genus (Cynopoecilus) in the Patos area of endemism has contributed to in-situ diversification of Austrolebias species.
Auteurs, date et publication :
Auteurs Tom Van Dooren , Henri A. Thomassen , Femmie Smit , Andrew J. Helmstetter , Vincent Savolainen
Publication : bioRxiv
Date : 2018
Pages : 121806
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
In the context of increasing population and decreasing acreages, the reduction in crop yields induced by tropospheric ozone should be better evaluated. Therefore, ozone-resistant and ˗sensitive tobacco (cv. Bel-B and Bel-W3), barley and rapeseed plants were submitted to ozone-enriched air, during pre-flowering period. Six ozone concentrations (ranging from 30 to 130 ppb for six hours during the photoperiod) and two treatment durations (1 or 2 weeks) were applied. These treatments correspond to low, moderate and high exposure levels that occurs in France. Several leaf parameters were measured: necrosis development, chlorophyll content, chlorophyll fluorescence (Fv/Fm, ΦPSII), gas exchange (carbon assimilation and leaf conductance), seed yield, and fatty acid composition in cell membranes. The fatty acid composition was used to calculate the "Omega-3 index", a biomarker based on stress-induced changes in leaf 18:3 content, developed to assess soil quality. To estimate the oxidative load in leaf tissues, quantification of targets of oxidative stress (such as intracellular proteins carbonylation) was rather used instead poorly reproductible ROS quantification. Results show that ozone treatments decrease chlorophyll content and omega-3 index. The extent of the declines and the threshold levels of ozone exposure triggering the declines observed in the different plant species studied will be discussed. Direct continuation of this study, will involve a water stress applied to the plants subsequent to the ozone treatments. The same physiological approach will then be used to characterize the plant responses to the combined stress treatments, to assess their resilience to drought after an ozone pollution episode.
Auteurs, date et publication :
Auteurs Ruben Puga-Freitas , Matthieu Bagard , Luis Leitao , Elodie Merlier , Christophe Espinasse , Anne Repellin , Jean-Jacques Bessoule , Marina Le Guédard , Amandine Hansart , Simon Chollet , Juliette Leymarie
Date : 2018
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENSRésumé
Nitrogen is an essential nutrient for life on Earth, but in excess, it can lead to environmental issues (e.g., N saturation, loss of biodiversity, acidification of lakes, etc.). Understanding the nitrogen budget (i.e., inputs and outputs) is essential to evaluate the prospective decay of the ecosystem services (e.g., freshwater quality, erosion control, loss of high patrimonial-value plant species, etc.) that subalpine headwater catchments provide, especially as these ecosystems experience high atmospheric nitrogen deposition. Here, we use a multi-isotopic tracer (Δ17O, δ15N and δ18O) of nitrate in aerosols, snow, and streams to assess the fate of atmospherically deposited nitrate in the subalpine watershed of the Lautaret Pass (French Alps). We show that atmospheric N deposition contributes significantly to stream nitrate pool year-round, either by direct inputs (up to 35%) or by in situ nitrification of atmospheric ammonium (up to 35%). Snowmelt in particular leads to high exports of atmospheric nitrate, most likely fast enough to impede assimilation by surrounding ecosystems. Yet, in a context of climate change, with shorter snow seasons, and increasing nitrogen emissions, our results hint at possibly stronger ecological consequences of nitrogen atmospheric deposition in the close future.
Auteurs, date et publication :
Auteurs Ilann Bourgeois , Joël Savarino , Nicolas Caillon , Hélène Angot , Albane Barbero , Franck Delbart , Didier Voisin , Jean-Christophe Clément
Publication : Environmental Science & Technology
Date : 2018
Volume : 52
Issue : 10
Pages : 5561-5570
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Continental atmospheric relative humidity (RH) is a key climate-parameter. Combined with atmospheric temperature, it allows us to estimate the concentration of atmospheric water vapor which is one of the main components of the global water cycle and the most important gas contributing to the natural greenhouse effect. However, there is a lack of proxies suitable for reconstructing, in a quantitative way, past changes of continental atmospheric humidity. This reduces the possibility to make model-data comparisons necessary for the implementation of climate models. Over the past 10 years, analytical developments have enabled a few laboratories to reach sufficient precision for measuring the triple oxygen isotopes, expressed by the 17O-excess (17O-excess = ln (δ17O + 1) − 0.528 × ln (δ18O + 1)), in water, water vapor and minerals. The 17O-excess represents an alternative to deuterium-excess for investigating relative humidity conditions that prevail during water evaporation. Phytoliths are micrometric amorphous silica particles that form continuously in living plants. Phytolith morphological assemblages from soils and sediments are commonly used as past vegetation and hydrous stress indicators. In the present study, we examine whether changes in atmospheric RH imprint the 17O-excess of phytoliths in a measurable way and whether this imprint offers a potential for reconstructing past RH. For that purpose, we first monitored the 17O-excess evolution of soil water, grass leaf water and grass phytoliths in response to changes in RH (from 40 to 100 %) in a growth chamber experiment where transpiration reached a steady state. Decreasing RH decreases the 17O-excess of phytoliths by 4.1 per meg / % as a result of kinetic fractionation of the leaf water subject to evaporation. In order to model with accuracy the triple oxygen isotope fractionation in play in plant water and in phytoliths we recommend direct and continuous measurements of the triple isotope composition of water vapor. Then, we measured the 17O-excess of 57 phytolith assemblages collected from top soils along a RH and vegetation transect in inter-tropical West and Central Africa. Although scattered, the 17O-excess of phytoliths decreases with RH by 3.4 per meg / %. The similarity of the trends observed in the growth chamber and nature supports that RH is an important control of 17O-excess of phytoliths in the natural environment. However, other parameters such as changes in the triple isotope composition of the soil water or phytolith origin in the leaf tissue may come into play. Assessment of these parameters through additional growth chambers experiments and field campaigns will bring us closer to an accurate proxy of changes in relative humidity.
Auteurs, date et publication :
Auteurs Anne Alexandre , Amarelle Landais , Christine Vallet-Coulomb , Clément Piel , Sébastien Devidal , Sandrine Pauchet , Corinne Sonzogni , Martine Couapel , Marine Pasturel , Pauline Cornuault , Jingming Xin , Jean-Charles Mazur , Frédéric Prié , Ilhem Bentaleb , Elizabeth Webb , Françoise Chalié , Jacques Roy
Publication : Biogeosciences Discussions
Date : 2025
Volume : 15
Pages : 3223–3241
Catégorie(s)
#CNRS #Ecotron de MontpellierRésumé
Abstract. At a local level, biogenic isoprene emissions can greatly affect the air quality of urban areas surrounded by large vegetation sources, such as in the Mediterranean region. The impacts of future warmer and drier conditions on isoprene emissions from Mediterranean emitters are still under debate. Seasonal variations of Quercus pubescens gas exchange and isoprene emission rates (ER) were studied from June 2012 to June 2013 at the O3HP site (French Mediterranean) under natural (ND) and amplified (AD, 32%) drought. While AD significantly reduced stomatal conductance to water vapour throughout the research period excluding August, it did not significantly preclude CO2 net assimilation, which was lowest in summer (µmolm−2s−1). ER followed a significant seasonal pattern regardless of drought intensity, with mean ER maxima of 78.5 and 104.8µgCgh−1 in July (ND) and August (AD) respectively and minima of 6 and <2µgCgh−1 in October and April respectively. The isoprene emission factor increased significantly by a factor of 2 in August and September under AD (137.8 and 74.3µgCgh−1) compared with ND (75.3 and 40.21µgCgh−1), but no significant changes occurred on ER. Aside from the June 2012 and 2013 measurements, the MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model was able to assess the observed ER variability only when its soil moisture activity factor γSM was not operating and regardless of the drought intensity; in this case more than 80% and 50% of ER seasonal variability was assessed in the ND and AD respectively. We suggest that a specific formulation of γSM be developed for the drought-adapted isoprene emitter, according to that obtained for Q. pubescens in this study (γSM=0.192e51.93 SW with SW the soil water content). An isoprene algorithm (G14) was developed using an optimised artificial neural network (ANN) trained on our experimental dataset (ER+O3HP climatic and edaphic parameters cumulated over 0 to 21 days prior to the measurements). G14 assessed more than 80% of the observed ER seasonal variations, regardless of the drought intensity. ERG14 was more sensitive to higher (0 to −7 days) frequency environmental changes under AD in comparison to ND. Using IPCC RCP2.6 and RCP8.5 climate scenarios, and SW and temperature as calculated by the ORCHIDEE land surface model, ERG14 was found to be mostly sensitive to future temperature and nearly insensitive to precipitation decrease (an annual increase of up to 240% and at the most 10% respectively in the most severe scenario). The main impact of future drier conditions in the Mediterranean was found to be an enhancement (+40%) of isoprene emissions sensitivity to thermal stress.
Auteurs, date et publication :
Auteurs Anne-Cyrielle Genard-Zielinski , Christophe Boissard , Elena Ormeño , Juliette Lathière , Ilja M. Reiter , Henri Wortham , Jean-Philippe Orts , Brice Temime-Roussel , Bertrand Guenet , Svenja Bartsch , Thierry Gauquelin , Catherine Fernandez
Publication : Biogeosciences
Date : 2018
Volume : 15
Issue : 15
Pages : 4711-4730
Catégorie(s)
#CNRS #FORET O3HPRésumé
Genome duplication is essential for cell proliferation, and the mechanisms regulating its execution are highly conserved. These processes give rise to a spatiotemporal organization of replication initiation across the genome, referred to as the replication program. Despite the identification of such programs in diverse eukaryotic organisms, their biological importance for cellular physiology remains largely unexplored. We address this fundamental question in the context of genome maintenance, taking advantage of the inappropriate origin firing that occurs when fission yeast cells lacking the Rad3/ATR checkpoint kinase are subjected to replication stress. Using this model, we demonstrate that the replication program quantitatively dictates the extent of origin de-regulation and the clustered localization of these events. Furthermore, our results uncover an accumulation of abnormal levels of single-stranded DNA (ssDNA) and the Rad52 repair protein at de-regulated origins. We show that these loci constitute a defining source of the overall ssDNA and Rad52 hotspots in the genome, generating a signature pattern of instability along the chromosomes. We then induce a genome-wide reprogramming of origin usage and evaluate its consequences in our experimental system. This leads to a complete redistribution of the sites of both inappropriate initiation and associated Rad52 recruitment. We therefore conclude that the organization of genome duplication governs the checkpoint control of origin-associated hotspots of instability and plays an integral role in shaping the landscape of genome maintenance.
Auteurs, date et publication :
Auteurs Blanca Gómez-Escoda , Pei-Yun Jenny Wu
Publication : Genome Research
Date : 2018
Volume : 28
Issue : 8
Pages : 1179-1192