Résumé
Eutrophication has been a major stressor in lakes during the last century, with important implications for fish populations and thus fisheries. We summarised the Arctic charr (Salvelinus alpinus) fishery data available in Lake Geneva between 1887 and 2011 to describe contemporary catches in a broad perspective in relationship to the trophic status and the stocking history. Actual catches are low, but such levels had already been reached before the period of eutrophication. In addition, the high catch levels during the 1990s appeared to be artificially boosted by intense stocking and therefore cannot be used as a reference point. Thus, fishery data only do not allow for population functionality inference. Subsequently, we evaluated the contemporary contribution of stocking to catches and to the spawners by marking all of the fingerlings stocked in 2007 (n = 993,300 individuals) with a mass marking otolith technique using alizarine Red S. Multiple markings allowed us to distinguish between three stocking practices and to compare their relative efficiency. From 2009 to 2011, 1929 charr were sampled in recreational catches, commercial catches, and in spawners. More than 51% (980) of the total sample set corresponded to the 2007 cohort. The total contribution of stocked fish was 84% at stage 2+, 72% at stage 3+, and 44% at stage 4+. The results were similar to prior values obtained during the 1980s. Differences in the contributions between the types of samples (commercial catches, recreational catches, and spawners) were found. The results highlighted the fact that the current stocking effectiveness was 4 to 5 times lower compared to the effectiveness during the 1980s. Consequently, the current concern about the Arctic charr population, and the fishery in Lake Geneva, is two-fold: first, the long process of reoligotrophication does not allow for the restoration of self-sustaining Arctic charr populations; second, the stocking effectiveness decreased strongly over the last 30 years. Even if stocking greatly contributes to catches, it still does not ensure a sustainable fishery at a high level.
Auteurs, date et publication :
Auteurs Arnaud Caudron , Emilien Lasne , Christian Gillet , Jean Guillard , Alexis Champigneulle
Publication : Fisheries Research
Date : 2025
Volume : 154
Pages : 165-171
Catégorie(s)
#INRAE #OLARésumé
Double-stranded DNA viruses infecting eukaryotic algae (e.g., phycodnaviruses) and cyanobacteria (e.g., cyanophages) are now recognized as widespread and ubiquitous in aquatic environments. However, both the diversity and functional roles of these viruses in fresh waters are still poorly understood. We conducted a yearlong study in 2011 of the community structure of planktonic virus groups in the upper lit layer of two important freshwater natural ecosystems in France, Lake Annecy (oligotrophic) and Lake Bourget (oligo-mesotrophic). Using PCR-DGGE to target a number of different structural and functional signature genes, i.e.,g20, g23, psbA, polB, and mcp, the phytoplankton viruses were shown to display temporal and spatial variability. There were marked seasonal changes in community structure for all viral groups in Lake Bourget, but only for T4-like myoviruses and psbA-containing cyanophages in Lake Annecy. The multivariate statistical analyses revealed that (1) various environmental factors can directly or indirectly explain the community structure observed for each phytoplankton viral group, and (2) temporal patterns of T4like myovirus community structure were similar between the two lakes. In general, our results (1) suggest that the observed algal virus patterns were associated with significant shifts in phytoplankton biomass and/or structure, which in turn were shaped by the abiotic environment, and (2) support the Bank model proposed by Breitbart and Rohwer (Trends Microbiol 13:278–284, 2005). This study provides new evidence that freshwater lakes contain a significant diversity of algal viruses, and that the distribution of these viruses strongly mirrors that of their hosts.
Auteurs, date et publication :
Auteurs X. Zhong , F. Rimet , S. Jacquet
Publication : Ecological Research
Date : 2025
Volume : 29
Issue : 2
Pages : 271-287
Catégorie(s)
#INRAE #OLAAuteurs, date et publication :
Auteurs Yannick Bayona , Ana Roucaute , Marc Roucaute , Caroline Gorzerino , Kevin Cailleaud , Laurent Lagadic , Anne Bassères , Thierry Caquet
Publication : Environmental Toxicology and Chemistry
Date : 2014
Pages : n/a-n/a
Catégorie(s)
#INRAE #PEARLRésumé
To determine the role of earthworms in regenerating compacted zones, it is essential to consider their capacity to colonise these zones. This study aimed to determine the short-term (3-4 years) response of earthworm populations to heavy traffic in two forest soils, at Azerailles (AZ) and Clermont-en-Argonne (CA) in north-eastern France. Earthworm populations were recorded immediately and for 3-4 years after heavy traffic by a 8-wheel drive forwarder with a load of about 23 Mg at AZ and 17 Mg at CA. To test the capacity of earthworms to recolonise traffic plot from the edges, an extra sampling was performed at the border of the traffic plots at AZ. Heavy traffic had a detrimental impact on the density and biomass of three earthworm functional groups. At AZ, earthworm populations, dominated by endogeic species, followed by anecic and epigeic species, had not fully recovered four years after compaction. The absence of statistically significant colonisation by the three functional groups from control to traffic plots indicated that the soil habitat was not yet favourable. At CA, earthworm populations, represented exclusively by epigeic species, had fully recovered three years after compaction, suggesting that the soil habitat was already suitable for them. This strong dependence on soil habitat quality is discussed and may be one reason for variation in the recovery rate of earthworms after compaction reported in the literature. In conclusion, this study did not support the hypothesis that earthworms play a role in regenerating soil structure the first few years following forest-soil compaction. (C) 2013 Elsevier B.V. All rights reserved.
Auteurs, date et publication :
Auteurs N. Bottinelli , Y. Capowiez , J. Ranger
Publication : Applied Soil Ecology
Date : 2014
Volume : 73
Pages : 130-133
Catégorie(s)
#FORET Azerailles-Clermont #INRAEAuteurs, date et publication :
Auteurs François Martignac , Aurélie Daroux , Jean-Luc Bagliniere , Dominique Ombredane , Jean Guillard
Publication : Fish and Fisheries
Date : 2014
Pages : n/a-n/a
Catégorie(s)
#INRAE #PEARLRésumé
The Geoscience Laser Altimeter System (GLAS) has provided a useful dataset for estimating forest heights in many areas of the globe. Most of the studies on GLAS waveforms have focused on natural forests and only a few were conducted over forest plantations. This work set out to estimate the stand-scale dominant height and aboveground biomass of intensively managed Eucalyptus plantations in Brazil using the most commonly used models developed for natural forests. These forest plantations are valuable case studies, with large and numerous stands that are very uniform, in which field measurements are precise compared to natural forests. The height of planted Eucalyptus forest stands estimated from waveforms acquired by GLAS were compared with in situ measurements in order to determine the model that produced the best forest height estimates. For our slightly sloping study site (slope < 7 degrees), the direct method defined as the difference between the signal begin and the ground peak provided forest height estimates with an accuracy of 2.2 m. The use of statistical models based on waveform metrics and digital elevation models provided slightly better results (1.89 m accuracy) in comparison with the direct method and the most relevant metrics proved to be the trailing edge extent and the waveform extent. Moreover, a power law model was used to fit in situ aboveground biomass to in situ forest height. The results using this model with GLAS-derived heights showed an accuracy for biomass of 16.1 Mg/ha.
Auteurs, date et publication :
Auteurs N. Baghdadi , G. le Maire , I. Fayad , J.-S. Bailly , Y. Nouvellon , C. Lemos , R. Hakamada
Publication : IEEE Geoscience and Remote Sensing Letters
Date : 2014
Volume : 7
Issue : 1
Pages : 290-299
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
Using nutrient budgets, it has been proven that atmospheric deposition of Mg and Ca sustains the fertility of forest ecosystems on base-poor soils. However the fate of this nutrient input within the ecosystem was presently unknown. Our hypothesis is that the biological cycling of these nutrients is very rapid and conservative to prevent further Mg and Ca losses most especially in ecosystems on base-poor soils. Stable isotopes of magnesium and calcium (Mg-26 and Ca-44) were used to trace the dynamics of throughfall Mg and Ca in the forest soil of a 35-year-old beech stand. The aim of the present study was to (1) understand the processes and the velocity of the incorporation of tracers in the biogeochemical cycles and (2) compute Mg and Ca budgets for the ecosystem by isotope dilution. Rainfall Mg and Ca were strongly and rapidly retained mainly by ion exchange in the thin OL litter-layer. However, Ca was much more strongly retained in the litter-layer than Mg. As a result, 2 years after the application of tracers (2012), 92 % of Mg-26 and 67 % of Ca-44 was released and transferred to the soil or taken up by trees. The vertical transfer of Mg was very slow only 15 % of Mg-26 was found below 15 cm depth in 2012. Ca was slower than Mg-26 only 9 % of Ca-44 was found below 5 cm depth. Although matrix flow was the main vertical transfer process of Ca and Mg, preferential transfer in macropores occurred. Overall, Mg was more rapidly leached through the soil profile than Ca because the soil CEC was mainly composed of organic charges which affinity for Ca is much higher than for Mg. 27 % of Mg-26 and 20 % of Ca-44 was found in tree biomass and total tracer recovery was close to 100 %. These results suggest that no tracers were lost to drainage over the 2 years. Finally, applying the isotopic dilution theory to the whole-ecosystem enabled us to estimate Mg and Ca budgets -0.9 kg ha(-1) year(-1) for Mg, which was close to computed input-output budgets -0.8 and 0 kg ha(-1) year(-1) for Ca, which was very different from input-output budgets (-3.1 kg ha(-1) year(-1)). Our results suggest that a Ca source is underestimated or not taken into account. Over all, organic matter of the litter-layer and in the soil profile played an essential role in the retention of throughfall Mg and Ca and their cycling within the forest ecosystem.
Auteurs, date et publication :
Auteurs Gregory van der Heijden , Arnaud Legout , Benoit Pollier , Jacques Ranger , Etienne Dambrine
Publication : Biogeochemistry
Date : 2014
Volume : 118
Issue : 1-3
Pages : 413-442
Catégorie(s)
#FORET Breuil #INRAERésumé
As wood harvests are expected to increase to satisfy the need for bio-energy in Europe, quantifying atmospheric nutrient inputs in forest ecosystems is essential for forest management. Current atmospheric measurements only take into account the 0.45μm fraction of atmospheric deposition, below the canopy, to study the influence of the canopy on APD, and to determine the influence of APD below canopy to nutrient input–output budgets with a focus on base cations calcium, magnesium and potassium, and phosphorus. APD was sampled every four weeks by passive collectors. We divided APD into an organic and a mineral fraction, respectively POM and MDD. MDD was divided into a soluble and a hardly soluble fraction in hydrogen peroxide, referred to as S-MDD and H-MDD, respectively. In order to better understand the influence of the canopy on APD, we studied APD in three pathways below the canopy (litterfall, stemflow and throughfall), and in open field. Our results indicated that APD in throughfall (123±64kgha−1year−1) was significantly higher and synchronic with that in open field (33±9kgha−1year−1) in the two study sites. This concerned both POM and MDD, suggesting a large interception of APD by foliar surfaces, which is rapidly washed off by rain within four weeks. Throughfall H-MDD was the main pathway with an average of 16±2kgha−1year−1. Stemflow and litterfall were neglected. In one study site, canopy intercepted about 8kgha−1year−1 of S-MDD. Although base cations and phosphorus inputs by APD are lower than those of <0.45μm deposition, they contributed from 5 to 32% to atmospheric deposition and improved the nutrient budget in one of the study sites.
Auteurs, date et publication :
Auteurs Emeline Lequy , Christophe Calvaruso , Sébastien Conil , Marie-Pierre Turpault
Publication : Science of The Total Environment
Date : 2014
Volume : 487
Pages : 206-215
Catégorie(s)
#FORET Breuil #FORET Montiers #INRAERésumé
Spatial scaling of microorganisms has been demonstrated over the last decade. However, the processes and environmental filters shaping soil microbial community structure on a broad spatial scale still need to be refined and ranked. Here, we compared bacterial and fungal community composition turnovers through a biogeographical approach on the same soil sampling design at a broad spatial scale (area range: 13300 to 31000 km2): i) to examine their spatial structuring; ii) to investigate the relative importance of environmental selection and spatial autocorrelation in determining their community composition turnover; and iii) to identify and rank the relevant environmental filters and scales involved in their spatial variations. Molecular fingerprinting of soil bacterial and fungal communities was performed on 413 soils from four French regions of contrasting environmental heterogeneity (Landes<Burgundy≤Brittany<<South-East) using the systematic grid of French Soil Quality Monitoring Network to evaluate the communities’ composition turnovers. The relative importance of processes and filters was assessed by distance-based redundancy analysis. This study demonstrates significant community composition turnover rates for soil bacteria and fungi, which were dependent on the region. Bacterial and fungal community composition turnovers were mainly driven by environmental selection explaining from 10% to 20% of community composition variations, but spatial variables also explained 3% to 9% of total variance. These variables highlighted significant spatial autocorrelation of both communities unexplained by the environmental variables measured and could partly be explained by dispersal limitations. Although the identified filters and their hierarchy were dependent on the region and organism, selection was systematically based on a common group of environmental variables: pH, trophic resources, texture and land use. Spatial autocorrelation was also important at coarse (80 to 120 km radius) and/or medium (40 to 65 km radius) spatial scales, suggesting dispersal limitations at these scales.
Auteurs, date et publication :
Auteurs Nicolas Chemidlin Prévost-Bouré , Samuel Dequiedt , Jean Thioulouse , Mélanie Lelièvre , Nicolas P. A. Saby , Claudy Jolivet , Dominique Arrouays , Pierre Plassart , Philippe Lemanceau , Lionel Ranjard
Publication : Plos One
Date : 2014
Volume : 9
Issue : 11
Pages : e111667
Catégorie(s)
#ANR-Citation #Genosol #INRAEAuteurs, date et publication :
Auteurs Sylvie Nazaret , Rustam Aminov
Publication : Frontiers in Microbiology
Date : 2014
Volume : 5