Résumé
Detailed studies of wind-driven interbasin exchange in lakes, focusing on the underlying driving forces and how they are affected by stratification, are presently lacking. We therefore investigated how stratification modifies wind-induced exchange between the Petit Lac (PL) (depth 75 m) and Grand Lac (GL) (depth 309 m) basins of Lake Geneva in winter, using field observations, 3D hydrodynamic modeling and particle tracking. Early, weakly-stratified (December) and late, fully-mixed (March) winter conditions in the PL were compared for a typical, strong along-axis wind forcing. During early winter, twolayer exchange develops between the basins, with downwind surface outflow into the GL balanced by intense bottom inflow of deep, cold hypolimnetic GL water into the PL which is enhanced by baroclinic pressure gradients caused by upwelling in the GL. Furthermore, the transversal water-level setup generates barotropic pressure gradients that balance Coriolis force acting on the outflow. This produces unidirectional along-wind epilimnion currents that strengthen interbasin exchange. In late winter, with the thermocline deeper than the PL bottom, upwelling in the GL does not reach the confluence and baroclinicity plays no role, resulting in weaker exchange currents with a depth-veering structure in the upper layers due to Coriolis force. In late winter, interbasin exchange decreases by 50 %, is more local, affects only waters near the confluence, and is more horizontal, with no deepwater upwelling from the GL. Our results suggest that prolonged winter stratification due to global warming will make wind-induced hypolimnetic interbasin-upwelling an increasingly important deepwater renewal process in large multi-depth basin lakes.
Auteurs, date et publication :
Auteurs Rafael Sebastian Reiss , Ulrich Lemmin , David Andrew Barry
Publication : Journal of Great Lakes Research
Date : 2025
Volume : 49
Issue : 2
Pages : 406-421
Catégorie(s)
#INRAE #OLARésumé
The European biodiversity and forest strategies rely on forest sustainable management (SFM) to conserve forest biodiversity. However, current sustainability assessments hardly account for direct biodiversity indicators. We focused on forest multi-taxon biodiversity to: i) gather and map the existing information; ii) identify knowledge and research gaps; iii) discuss its research potential. We established a research network to fit data on species, standing trees, lying deadwood and sampling unit description from 34 local datasets across 3591 sampling units. A total of 8724 species were represented, with the share of common and rare species varying across taxonomic classes: some included many species with several rare ones (e.g., Insecta); others (e.g., Bryopsida) were repre sented by few common species. Tree-related structural attributes were sampled in a subset of sampling units (2889; 2356; 2309 and 1388 respectively for diameter, height, deadwood and microhabitats). Overall, multitaxon studies are biased towards mature forests and may underrepresent the species related to other develop mental phases. European forest compositional categories were all represented, but beech forests were overrepresented as compared to thermophilous and boreal forests. Most sampling units (94%) were referred to a habitat type of conservation concern. Existing information may support European conservation and SFM stra tegies in: (i) methodological harmonization and coordinated monitoring; (ii) definition and testing of SFM in dicators and thresholds; (iii) data-driven assessment of the effects of environmental and management drivers on multi-taxon forest biological and functional diversity, (iv) multi-scale forest monitoring integrating in-situ and remotely sensed information.
Auteurs, date et publication :
Auteurs Sabina Burrascano , Francesco Chianucci , Giovanni Trentanovi , Sebastian Kepfer-Rojas , Tommaso Sitzia , Flóra Tinya , Inken Doerfler , Yoan Paillet , Thomas Andrew Nagel , Bozena Mitic , Lourdes Morillas , Silvana Munzi , Theo Van Der Sluis , Edoardo Alterio , Lorenzo Balducci , Rafael Barreto De Andrade , Christophe Bouget , Paolo Giordani , Thibault Lachat , Dinka Matosevic
Publication : Biological Conservation
Date : 2025
Volume : 284
Pages : 110176
Catégorie(s)
#FORET OPTMix #INRAERésumé
The stability of grazing-induced spatial patterns of vegetation was analyzed at two spatial scales (25m×20m areas and 1.6m×0.8m grids) in pastures of contrasting productivity (maximum standing biomass: 130–800gDM/m2). At both scales, the mosaic of grazed and ungrazed patches was modeled as a Boolean process, calculating cross-variograms to quantify the temporal stability of grazing patterns and its links with local floristic composition were tested. The scale at which stability of vegetation patterns took place in two successive years depended on pasture productivity. Inter-annual stability of large-scale patterns mainly occurred in extensively used fertile pastures grazed by cattle, and in pastures grazed by horses. Less-fertile grasslands were mainly characterized by a fine-scale stability of grazing patterns. Stable fine-scale patterns were often related to the local abundance of legumes and forbs. Stable large-scale patterns of grazing within lightly grazed productive grasslands could result in divergent local vegetation dynamics, which can be seen as an opportunity for restoring biodiversity in fertile grasslands.
Auteurs, date et publication :
Auteurs Bertrand Dumont , Nicolas Rossignol , Grégory Loucougaray , Pascal Carrère , Joël Chadoeuf , Géraldine Fleurance , Anne Bonis , Anne Farruggia , Stéphanie Gaucherand , Cécile Ginane , Frédérique Louault , Benoit Marion , François Mesléard , Nicole Yavercovski
Publication : Agriculture, Ecosystems & Environment
Date : 2012
Volume : 153
Pages : 50-56
Catégorie(s)
#ACBB #ACBB Theix #INRAERésumé
Combining field measurements, 3-D numerical modeling, and Lagrangian particle tracking, we investigated wind-driven, Ekman-type coastal upwelling during the weakly stratified winter period 2017/2018 in Lake Geneva, Western Europe's largest lake (max. depth 309 m). Strong alongshore wind stress, persistent for more than 7 days, led to tilting and surfacing of the thermocline (initial depth 75-100 m). Observed nearshore temperatures dropped by 1 degrees C and remained low for 10 days, with the lowest temperatures corresponding to those of hypolimnetic waters originating from 200 m depth. Nearshore current measurements at 30 m depth revealed dominant alongshore currents in the entire water column (maximum current speed 25 cm s(-1)) with episodic upslope transport of cold hypolimnetic waters in the lowest 10 m mainly during the first 3 days. The observed upwelling dynamics were well reproduced by a 3-D hydrodynamic model (RMSE 0.2 degrees C), whose results indicated that upwelled waters spread over approximately 10% of the lake's main basin surface area. Model-based Lagrangian particle tracking confirmed that upwelled waters originated from far below the thermocline, that is, >150 m depth, and descended back to around 150-200 m depth over a wide area after wind stress ceased. Observational and particle tracking results suggest that wintertime coastal upwelling, which can occur several times during winter, is an overlooked transport process that is less sensitive to the effects of global warming than convective cooling. It can provide an effective but complex 3-D pathway for deepwater renewal in Lake Geneva, and other large, deep lakes with a sufficiently long wind fetch. Plain Language Summary Freshwater lakes are increasingly important as drinking water sources and for societal and economic activities. To maintain good water quality, deepwater renewal is essential for lake ecosystems. Traditionally, convectively driven vertical mixing during wintertime is considered as one of the main processes for deepwater renewal. In deep lakes, this mixing often cannot reach down to the deepest layers. Since this situation is expected to worsen due to climate change-induced warming, a good understanding of alternative deepwater renewal processes is crucial. We investigate wind-driven coastal upwelling of hypolimnetic water during the weakly stratified winter period. The study was carried out in monomictic Lake Geneva, a large, deep lake (depth 309 m), combining field observations, 3-D hydrodynamic modeling, and Lagrangian particle tracking, an effective combination for addressing the complex 3-D upwelling dynamics over a large area of the lake. We show that coastal upwelling can lift water masses from far below the thermocline up to the surface in the nearshore region, where they spend up to 5 days before descending back to the deeper layers. Our results demonstrate that wintertime coastal upwelling, an as yet overlooked transport process, can efficiently contribute to the renewal and aeration of the deepwater layer in deep lakes.
Auteurs, date et publication :
Auteurs Rafael S. Reiss , U. Lemmin , A. A. Cimatoribus , D. A. Barry
Publication : JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
Date : 2020
Volume : 125
Issue : 8
Catégorie(s)
#ANR-Citation #INRAE #OLARésumé
The effects of different anthropic activities (vineyard: phytosanitary protection; winery: pressing and sulfiting) on the fungal populations of grape berries were studied. The global diversity of fungal populations (moulds and yeasts) was performed by pyrosequencing. The anthropic activities studied modified fungal diversity. Thus, a decrease in biodiversity was measured for three successive vintages for the grapes of the plot cultivated with Organic protection compared to plots treated with Conventional and Ecophyto protections. The fungal populations were then considerably modified by the pressing-clarification step. The addition of sulfur dioxide also modified population dynamics and favoured the domination of the species Saccharomyces cerevisiae during fermentation. The non-targeted chemical analysis of musts and wines by FT-ICR-MS showed that the wines could be discriminated at the end of alcoholic fermentation as a function of adding SO2 or not, but also and above all as a function of phytosanitary protection, regardless of whether these fermentations took place in the presence of SO2 or not. Thus, the existence of signatures in wines of chemical diversity and microbiology linked to vineyard protection has been highlighted.
Auteurs, date et publication :
Auteurs Cédric Grangeteau , Chloé Roullier-Gall , Sandrine Rousseaux , Régis D. Gougeon , Philippe Schmitt-Kopplin , Hervé Alexandre , Michèle Guilloux-Benatier
Publication : Microbial Biotechnology
Date : 2016
Pages : n/a-n/a
Catégorie(s)
#Genosol #INRAERésumé
Combining field observations, 3D hydrodynamic modeling, and particle tracking, we investigated wind-induced interbasin exchange between the Petit Lac (PL) (depth 75 m) and Grand Lac (GL) (depth 309 m) basins of Lake Geneva in early winter. Following a strong 2.5-day wind event, a two-layer flow field developed, where the downwind surface drift into the GL was balanced by counterflowing hypolimnetic currents into the PL. Velocities in both layers exceeded 20 cm s −1, with the highest values (27 cm s −1) found near the bottom. For 3.5 days, hypolimnetic temperatures at the confluence decreased to values found in the deep GL hypolimnion at 180-m depth. Approximately 1.5 days after the wind event ceased, currents reversed and upwelled waters returned into the deep GL hypolimnion. The Coriolis force strongly modified the interbasin exchange dynamics, which were well represented by the model. Particle tracking revealed a “current loop,” that is, water from below 150-m depth first upwelled into the PL, intruded approximately 10 km (half its length), and then descended back into the GL hypolimnion. Model results showed that the PL hypolimnetic volume doubled during the upwelling. Low model-based gradient Richardson numbers and temperature inversions in CTD profiles indicated turbulent mixing between the upwelled GL and surrounding PL waters. Our findings demonstrate that hypolimnetic upwelling between the two basins frequently occurs during winter and could potentially be an important, but as yet overlooked mechanism for hypolimnetic-epilimnetic exchange and deepwater renewal in Lake Geneva, and probably in other multi-depth basin lakes under similar wind conditions.
Auteurs, date et publication :
Auteurs Rafael S. Reiss , U. Lemmin , D. A. Barry
Publication : Journal of Geophysical Research: Oceans
Date : 2025
Volume : 127
Issue : 6
Catégorie(s)
#INRAE #OLAAuteurs, date et publication :
Auteurs Stephen F. Jane , Gretchen J. A. Hansen , Benjamin M. Kraemer , Peter R. Leavitt , Joshua L. Mincer , Rebecca L. North , Rachel M. Pilla , Jonathan T. Stetler , Craig E. Williamson , R. Iestyn Woolway , Lauri Arvola , Sudeep Chandra , Curtis L. DeGasperi , Laura Diemer , Julita Dunalska , Oxana Erina , Giovanna Flaim , Hans-Peter Grossart , K. David Hambright , Catherine Hein
Publication : Nature
Date : 2021
Volume : 594
Issue : 7861
Pages : 66-70
Catégorie(s)
#INRAE #OLAAuteurs, date et publication :
Auteurs Dan Binkley , Jean-Paul Laclau , Hubert Sterba
Publication : Forest Ecology and Management
Date : 2025
Volume : 288
Pages : 1-4
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
DNA metabarcoding can be a promising alternative to microscopy for analysing phytoplankton, a key ecological indicator for freshwater ecosystems. The aim of this study was to evaluate the performance of different barcodes and associated primer pairs to assess microalgal diversity with DNA metabarcoding using a single barcode targeting all microalgae. We investigated barcodes in 16S and 23S rRNA genes, encoding for prokaryotic ribosomal sub-units, that are present in Cyanobacteria as well as in chloroplasts. In silico PCR tests were carried out on eight 16S and five 23S primer pairs using the Phytool reference library. Two and three pairs were selected for 16S and 23S, respectively, to perform an in vitro metabarcoding test based on a mock community made of DNA extracts of 10 microalgae strains. The 23S pairs enabled to detect all species, whereas 16S ones failed in the detection of some of them. One pair was selected for each genetic marker, based on its efficiency and specificity towards microalgae (e.g. not heterotrophic bacteria). Another mock community covering a larger diversity (18 microalgae strains) was used to test the efficiency of the selected pairs and their ability to estimate relative abundances. The 23S pair performed better than the 16S one for detecting target species with also more accuracy to assess their relative abundances. We conclude that the 23S primer pair ECLA23S_F1/ECLA23S_R1 appears as a good candidate to decipher freshwater phytoplankton communities. As a next step, it will be necessary to confirm these results on a large diversity of natural communities.
Auteurs, date et publication :
Auteurs Alexis Canino , Clarisse Lemonnier , Benjamin Alric , Agnès Bouchez , Isabelle Domaizon , Christophe Laplace-Treyture , Frédéric Rimet
Publication : International Journal of Limnology
Date : 2025
Volume : 59
Pages : 8
Catégorie(s)
#INRAE #OLARésumé
Heterogeneity of structure can increase mechanical stability, stress resistance and resilience, biodiversity and many other functions and services of forest stands. That is why many silvicultural measures aim at enhancing structural diversity. However, the effectiveness and potential of structuring may depend on the site conditions. Here, we revealed how the stand structure is determined by site quality and results from site-dependent partitioning of growth and mortality among the trees. We based our study on 90 mature, even-aged, fully stocked monocultures of Scots pine (Pinus sylvestris L.) sampled in 21 countries along a productivity gradient across Europe. A mini-simulation study further analyzed the site-dependency of the interplay between growth and mortality and the resulting stand structure. The overarching hypothesis was that the stand structure changes with site quality and results from the site-dependent asymmetry of competition and mortality. First, we show that Scots pine stands structure across Europe become more homogeneous with increasing site quality. The coefficient of variation and Gini coefficient of stem diameter and tree height continuously decreased, whereas Stand Density Index and stand basal area increased with site index. Second, we reveal a site-dependency of the growth distribution among the trees and the mortality. With increasing site index, the asymmetry of both competition and growth distribution increased and suggested, at first glance, an increase in stand heterogeneity. However, with increasing site index, mortality eliminates mainly small instead of all-sized trees, cancels the size variation and reduces the structural heterogeneity. Third, we modelled the site-dependent interplay between growth partitioning and mortality. By scenario runs for different site conditions, we can show how the site-dependent structure at the stand level emerges from the asymmetric competition and mortality at the tree level and how the interplay changes with increasing site quality across Europe. Our most interesting finding was that the growth partitioning became more asymmetric and structuring with increasing site quality, but that the mortality eliminated predominantly small trees, reduced their size variation and thus reversed the impact of site quality on the structure. Finally, the reverse effects of mode of growth partitioning and mortality on the stand structure resulted in the highest size variation on poor sites and decreased structural heterogeneity with increasing site quality. Since our results indicate where heterogeneous structures need silviculture interventions and where they emerge naturally, we conclude that these findings may improve system understanding and modelling and guide forest management aiming at structurally rich forests.
Auteurs, date et publication :
Auteurs Hans Pretzsch , Andrés Bravo-Oviedo , Torben Hilmers , Ricardo Ruiz-Peinado , Lluís Coll , Magnus Löf , Shamim Ahmed , Jorge Aldea , Christian Ammer , Admir Avdagić , Ignacio Barbeito , Kamil Bielak , Felipe Bravo , Gediminas Brazaitis , Jakub Cerný , Catherine Collet , Lars Drössler , Marek Fabrika , Michael Heym , Stig-Olof Holm
Publication : Forest Ecology and Management
Date : 2022
Volume : 520
Pages : 120365