30 research outputs found
Prédiction de la sensibilité biogéochimique et écologique des écosystÚmes forestiers français aux dépÎts atmosphériques azotés dans un contexte de changement global
Depuis des dĂ©cennies, les dĂ©pĂŽts atmosphĂ©riques azotĂ©s sont connus pour agir de maniĂšre sĂ©vĂšre sur le fonctionnement des Ă©cosystĂšmes forestiers. Ils influent en effet la biogĂ©ochimie du sol, lâĂ©quilibre des Ă©lĂ©ments nutritifs et, en consĂ©quence, la croissance des espĂšces vĂ©gĂ©tales, la biodiversitĂ© vĂ©gĂ©tale de sous-Ă©tage et plus globalement la santĂ© des forĂȘts. Dans le cadre de la convention internationale de GenĂšve visant Ă limiter la pollution atmosphĂ©rique transfrontaliĂšre Ă longue distance, le concept de « Charges Critiques », dĂ©fini Ă la fin des annĂ©es 1980, a Ă©tĂ© retenu comme outil permettant dâĂ©valuer la sensibilitĂ© dâun Ă©cosystĂšme aux contaminants. Il permet dâestimer la quantitĂ© maximale de polluants atmosphĂ©riques acceptable par lâĂ©cosystĂšme avant apparition de consĂ©quences nĂ©fastes Ă son fonctionnement. De plus, en raison de lâimpact des changements globaux sur les processus biogĂ©ochimiques rĂ©gissant le fonctionnement des Ă©cosystĂšmes, lâinfluence des dĂ©pĂŽts atmosphĂ©riques et du changement climatique doit ĂȘtre considĂ©rĂ© de maniĂšre simultanĂ©e pour Ă©valuer lâĂ©volution de lâĂ©tat des Ă©cosystĂšmes au cours du temps. DĂšs lors lâenjeu majeur est de pouvoir prĂ©dire lâeffet combinĂ© de ces facteurs sur les Ă©cosystĂšmes forestiers français. Câest lâobjectif de ce travail de thĂšse. Des modĂšles dynamiques couplĂ©s biogĂ©ochimiques â Ă©cologiques, tels que les modĂšles ForSAFE-VEG ou PROPS, ou Ă©cologiques (basĂ©s sur la base de donnĂ©es EcoPlant) ont Ă©tĂ© dĂ©veloppĂ©s ou adaptĂ©s Ă ces fins, et appliquĂ©s Ă diffĂ©rentes Ă©chelles locale, rĂ©gionale et nationale, selon diffĂ©rents scĂ©narios de dĂ©pĂŽts et climatiques. Lâapplication et la calibration du modĂšle couplĂ© ForSAFE-VEG sur des placettes forestiĂšres permanentes du rĂ©seau RENECOFOR ont permis de prĂ©dire lâĂ©volution de la composition biogĂ©ochimique de la solution du sol et en cascade de la composition floristique de trois sites, sous diffĂ©rents scĂ©narios de dĂ©pĂŽts atmosphĂ©riques et de changement climatique. Les principales Ă©volutions des sites sont liĂ©es Ă leurs caractĂ©ristiques stationnelles. Si le changement climatique joue un rĂŽle prĂ©dominant sur la rĂ©ponse des espĂšces, les Ă©cosystĂšmes oligotrophes restent sensibles aux dĂ©pĂŽts de N. A court terme, lâeffet combinĂ© des dĂ©pĂŽts et du changement climatique sur le long terme est modulĂ© par les effets de la gestion forestiĂšre. Lâextrapolation du modĂšle couplĂ© Ă plus large Ă©chelle nĂ©cessite une continuitĂ© dans la disponibilitĂ© des donnĂ©es dâentrĂ©e et de calibration de la rĂ©ponse des espĂšces. Les donnĂ©es et scĂ©narios de changement climatiques ont Ă©tĂ© complĂ©tĂ©s et actualisĂ©s Ă lâaide du modĂšle SAFRAN et des nouveaux scĂ©narios RCP rĂ©gionalisĂ©s. La calibration de la rĂ©ponse des espĂšces vĂ©gĂ©tales Ă lâĂ©chelle de la France a Ă©tĂ© rĂ©alisĂ©e Ă partir des mesures de la base de donnĂ©es phytoĂ©cologiques EcoPlant, par le dĂ©veloppement de modĂšles de distribution dâespĂšces (SDM), en intĂ©grant simultanĂ©ment des variables climatiques, Ă©daphiques, dâĂ©nergie et de nutrition. Le couplage entre le modĂšle ForSAFE et les SDM assure une modĂ©lisation robuste Ă lâĂ©chelle du territoire de la rĂ©ponse des Ă©cosystĂšmes forestiers dans le temps, calibrĂ©e pour les conditions pĂ©doclimatiques françaises. La modĂ©lisation des charges critiques dâaciditĂ©, dâeutrophisation et de biodiversitĂ© sur lâensemble des sites RENECOFOR et la totalitĂ© des Ă©cosystĂšmes forestiers français montre des sensibilitĂ©s variĂ©es aux dĂ©pĂŽts de soufre et dâazote en fonction des Ă©cosystĂšmes, avec parmi les plus sensibles les Landes, la Sologne et le Massif Central. Des indices de qualitĂ© des habitats (HSi) ont Ă©tĂ© calculĂ©s Ă lâĂ©chelle de tous les Ă©cosystĂšmes par le modĂšle PROPS et les SDM. La sĂ©lection des espĂšces reprĂ©sentatives reste primordiale car elle conditionne la valeur finale de HSi. Ce paramĂštre est lâun des plus sensibles Ă prendre en compte dans la modĂ©lisation. Il est Ă mettre en relation avec les objectifs de protection des Ă©cosystĂšmes voulus par les gestionnaires
Combined effect of atmospheric nitrogen deposition and climate change on temperate forest soil biogeochemistry: A modeling approach
International audienceAtmospheric N deposition is known to severely impact forest ecosystem functioning by influencing soil biogeochemistry and nutrient balance, and consequently tree growth and overall forest health and biodiversity. Moreover, because climate greatly influences soil processes, climate change and atmospheric N deposition must both be taken into account when analysing the evolution of forest ecosystem status over time. Dynamic biogeochemical models have been developed to test different climate and atmospheric N deposition scenarios and their potential interactions in the long term. In this study, the ForSAFE model was used to predict the combined effect of atmospheric N deposition and climate change on two temperate forest ecosystems in France dominated by oak and spruce, and more precisely on forest soil biogeochemistry, from today to 2100. After a calibration step and following a careful statistical validation process, two atmospheric N deposition scenarios were tested: the current legislation in Europe (CLE) and the maximum feasible reduction (MFR) scenarios. They were combined with three climate scenarios: current climate scenario, worst-case climate scenario (A2) and best-case climate scenario (B1). The changes in base saturation and inorganic N concentration in the soil solution were compared across all scenario combinations, with the aim of forecasting the state of acidification, eutrophication and forest ecosystem recovery up to the year 2100. Simulations highlighted that climate had a stronger impact on soil base saturation, whereas atmospheric deposition had a comparative effect or a higher effect than climate on N concentration in the soil solution. Although deposition remains the main factor determining the evolution of N concentration in soil solution, increased temperature had a significant effect. Results also highlighted the necessity of considering the joint effect of both climate and atmospheric N deposition on soil biogeochemistry
Impact of safety-related dose reductions or discontinuations on sustained virologic response in HCV-infected patients: Results from the GUARD-C Cohort
BACKGROUND:
Despite the introduction of direct-acting antiviral agents for chronic hepatitis C virus (HCV) infection, peginterferon alfa/ribavirin remains relevant in many resource-constrained settings. The non-randomized GUARD-C cohort investigated baseline predictors of safety-related dose reductions or discontinuations (sr-RD) and their impact on sustained virologic response (SVR) in patients receiving peginterferon alfa/ribavirin in routine practice.
METHODS:
A total of 3181 HCV-mono-infected treatment-naive patients were assigned to 24 or 48 weeks of peginterferon alfa/ribavirin by their physician. Patients were categorized by time-to-first sr-RD (Week 4/12). Detailed analyses of the impact of sr-RD on SVR24 (HCV RNA <50 IU/mL) were conducted in 951 Caucasian, noncirrhotic genotype (G)1 patients assigned to peginterferon alfa-2a/ribavirin for 48 weeks. The probability of SVR24 was identified by a baseline scoring system (range: 0-9 points) on which scores of 5 to 9 and <5 represent high and low probability of SVR24, respectively.
RESULTS:
SVR24 rates were 46.1% (754/1634), 77.1% (279/362), 68.0% (514/756), and 51.3% (203/396), respectively, in G1, 2, 3, and 4 patients. Overall, 16.9% and 21.8% patients experienced 651 sr-RD for peginterferon alfa and ribavirin, respectively. Among Caucasian noncirrhotic G1 patients: female sex, lower body mass index, pre-existing cardiovascular/pulmonary disease, and low hematological indices were prognostic factors of sr-RD; SVR24 was lower in patients with 651 vs. no sr-RD by Week 4 (37.9% vs. 54.4%; P = 0.0046) and Week 12 (41.7% vs. 55.3%; P = 0.0016); sr-RD by Week 4/12 significantly reduced SVR24 in patients with scores <5 but not 655.
CONCLUSIONS:
In conclusion, sr-RD to peginterferon alfa-2a/ribavirin significantly impacts on SVR24 rates in treatment-naive G1 noncirrhotic Caucasian patients. Baseline characteristics can help select patients with a high probability of SVR24 and a low probability of sr-RD with peginterferon alfa-2a/ribavirin
Impact of Safety-Related Dose Reductions or Discontinuations on Sustained Virologic Response in HCV-Infected Patients: Results from the GUARD-C Cohort.
BACKGROUND: Despite the introduction of direct-acting antiviral agents for chronic hepatitis C virus (HCV) infection, peginterferon alfa/ribavirin remains relevant in many resource-constrained settings. The non-randomized GUARD-C cohort investigated baseline predictors of safety-related dose reductions or discontinuations (sr-RD) and their impact on sustained virologic response (SVR) in patients receiving peginterferon alfa/ribavirin in routine practice. METHODS: A total of 3181 HCV-mono-infected treatment-naive patients were assigned to 24 or 48 weeks of peginterferon alfa/ribavirin by their physician. Patients were categorized by time-to-first sr-RD (Week 4/12). Detailed analyses of the impact of sr-RD on SVR24 (HCV RNA <50 IU/mL) were conducted in 951 Caucasian, noncirrhotic genotype (G)1 patients assigned to peginterferon alfa-2a/ribavirin for 48 weeks. The probability of SVR24 was identified by a baseline scoring system (range: 0-9 points) on which scores of 5 to 9 and <5 represent high and low probability of SVR24, respectively. RESULTS: SVR24 rates were 46.1% (754/1634), 77.1% (279/362), 68.0% (514/756), and 51.3% (203/396), respectively, in G1, 2, 3, and 4 patients. Overall, 16.9% and 21.8% patients experienced â„1 sr-RD for peginterferon alfa and ribavirin, respectively. Among Caucasian noncirrhotic G1 patients: female sex, lower body mass index, pre-existing cardiovascular/pulmonary disease, and low hematological indices were prognostic factors of sr-RD; SVR24 was lower in patients with â„1 vs. no sr-RD by Week 4 (37.9% vs. 54.4%; P = 0.0046) and Week 12 (41.7% vs. 55.3%; P = 0.0016); sr-RD by Week 4/12 significantly reduced SVR24 in patients with scores <5 but not â„5. CONCLUSIONS: In conclusion, sr-RD to peginterferon alfa-2a/ribavirin significantly impacts on SVR24 rates in treatment-naive G1 noncirrhotic Caucasian patients. Baseline characteristics can help select patients with a high probability of SVR24 and a low probability of sr-RD with peginterferon alfa-2a/ribavirin.This study was sponsored by F. Hoffmann-La Roche Ltd, Basel, Switzerland. Support for third-party writing
assistance for this manuscript, furnished by Blair Jarvis MSc, ELS, of Health Interactions, was provided by F. Hoffmann-La Roche Ltd, Basel, Switzerland
Impact of safety-related dose reductions or discontinuations on sustained virologic response in HCV-infected patients: Results from the GUARD-C Cohort
Background: Despite the introduction of direct-acting antiviral agents for chronic hepatitis C virus (HCV) infection, peginterferon alfa/ribavirin remains relevant in many resource-constrained settings. The non-randomized GUARD-C cohort investigated baseline predictors of safety-related dose reductions or discontinuations (sr-RD) and their impact on sustained virologic response (SVR) in patients receiving peginterferon alfa/ribavirin in routine practice. Methods: A total of 3181 HCV-mono-infected treatment-naive patients were assigned to 24 or 48 weeks of peginterferon alfa/ribavirin by their physician. Patients were categorized by time-to-first sr-RD (Week 4/12). Detailed analyses of the impact of sr-RD on SVR24 (HCV RNA <50 IU/mL) were conducted in 951 Caucasian, noncirrhotic genotype (G)1 patients assigned to peginterferon alfa-2a/ribavirin for 48 weeks. The probability of SVR24 was identified by a baseline scoring system (range: 0-9 points) on which scores of 5 to 9 and <5 represent high and low probability of SVR24, respectively. Results: SVR24 rates were 46.1 % (754/1634), 77.1% (279/362), 68.0% (514/756), and 51.3% (203/396), respectively, in G1,2, 3, and 4 patients. Overall, 16.9% and 21.8% patients experienced 651 sr-RD for peginterferon alfa and ribavirin, respectively. Among Caucasian noncirrhotic G1 patients: female sex, lower body mass index, pre-existing cardiovascular/pulmonary disease, and low hematological indices were prognostic factors of sr-RD; SVR24 was lower in patients with 651 vs. no sr-RD by Week 4 (37.9% vs. 54.4%; P = 0.0046) and Week 12 (41.7% vs. 55.3%; P = 0.0016); sr-RD by Week 4/12 significantly reduced SVR24 in patients with scores <5 but not 655. Conclusions: In conclusion, sr-RD to peginterferon alfa-2a/ribavirin significantly impacts on SVR24 rates in treatment-naive G1 noncirrhotic Caucasian patients. Baseline characteristics can help select patients with a high probability of SVR24 and a low probability of sr-RD with peginter-feron alfa-2a/ribavirin
Predicting french forest ecosystems biogeochemical and ecological sensitivity to atmospheric nitrogen deposition in a context of global change
Depuis des dĂ©cennies, les dĂ©pĂŽts atmosphĂ©riques azotĂ©s sont connus pour agir de maniĂšre sĂ©vĂšre sur le fonctionnement des Ă©cosystĂšmes forestiers. Ils influent en effet la biogĂ©ochimie du sol, lâĂ©quilibre des Ă©lĂ©ments nutritifs et, en consĂ©quence, la croissance des espĂšces vĂ©gĂ©tales, la biodiversitĂ© vĂ©gĂ©tale de sous-Ă©tage et plus globalement la santĂ© des forĂȘts. Dans le cadre de la convention internationale de GenĂšve visant Ă limiter la pollution atmosphĂ©rique transfrontaliĂšre Ă longue distance, le concept de « Charges Critiques », dĂ©fini Ă la fin des annĂ©es 1980, a Ă©tĂ© retenu comme outil permettant dâĂ©valuer la sensibilitĂ© dâun Ă©cosystĂšme aux contaminants. Il permet dâestimer la quantitĂ© maximale de polluants atmosphĂ©riques acceptable par lâĂ©cosystĂšme avant apparition de consĂ©quences nĂ©fastes Ă son fonctionnement. De plus, en raison de lâimpact des changements globaux sur les processus biogĂ©ochimiques rĂ©gissant le fonctionnement des Ă©cosystĂšmes, lâinfluence des dĂ©pĂŽts atmosphĂ©riques et du changement climatique doit ĂȘtre considĂ©rĂ© de maniĂšre simultanĂ©e pour Ă©valuer lâĂ©volution de lâĂ©tat des Ă©cosystĂšmes au cours du temps. DĂšs lors lâenjeu majeur est de pouvoir prĂ©dire lâeffet combinĂ© de ces facteurs sur les Ă©cosystĂšmes forestiers français. Câest lâobjectif de ce travail de thĂšse. Des modĂšles dynamiques couplĂ©s biogĂ©ochimiques â Ă©cologiques, tels que les modĂšles ForSAFE-VEG ou PROPS, ou Ă©cologiques (basĂ©s sur la base de donnĂ©es EcoPlant) ont Ă©tĂ© dĂ©veloppĂ©s ou adaptĂ©s Ă ces fins, et appliquĂ©s Ă diffĂ©rentes Ă©chelles locale, rĂ©gionale et nationale, selon diffĂ©rents scĂ©narios de dĂ©pĂŽts et climatiques. Lâapplication et la calibration du modĂšle couplĂ© ForSAFE-VEG sur des placettes forestiĂšres permanentes du rĂ©seau RENECOFOR ont permis de prĂ©dire lâĂ©volution de la composition biogĂ©ochimique de la solution du sol et en cascade de la composition floristique de trois sites, sous diffĂ©rents scĂ©narios de dĂ©pĂŽts atmosphĂ©riques et de changement climatique. Les principales Ă©volutions des sites sont liĂ©es Ă leurs caractĂ©ristiques stationnelles. Si le changement climatique joue un rĂŽle prĂ©dominant sur la rĂ©ponse des espĂšces, les Ă©cosystĂšmes oligotrophes restent sensibles aux dĂ©pĂŽts de N. A court terme, lâeffet combinĂ© des dĂ©pĂŽts et du changement climatique sur le long terme est modulĂ© par les effets de la gestion forestiĂšre. Lâextrapolation du modĂšle couplĂ© Ă plus large Ă©chelle nĂ©cessite une continuitĂ© dans la disponibilitĂ© des donnĂ©es dâentrĂ©e et de calibration de la rĂ©ponse des espĂšces. Les donnĂ©es et scĂ©narios de changement climatiques ont Ă©tĂ© complĂ©tĂ©s et actualisĂ©s Ă lâaide du modĂšle SAFRAN et des nouveaux scĂ©narios RCP rĂ©gionalisĂ©s. La calibration de la rĂ©ponse des espĂšces vĂ©gĂ©tales Ă lâĂ©chelle de la France a Ă©tĂ© rĂ©alisĂ©e Ă partir des mesures de la base de donnĂ©es phytoĂ©cologiques EcoPlant, par le dĂ©veloppement de modĂšles de distribution dâespĂšces (SDM), en intĂ©grant simultanĂ©ment des variables climatiques, Ă©daphiques, dâĂ©nergie et de nutrition. Le couplage entre le modĂšle ForSAFE et les SDM assure une modĂ©lisation robuste Ă lâĂ©chelle du territoire de la rĂ©ponse des Ă©cosystĂšmes forestiers dans le temps, calibrĂ©e pour les conditions pĂ©doclimatiques françaises. La modĂ©lisation des charges critiques dâaciditĂ©, dâeutrophisation et de biodiversitĂ© sur lâensemble des sites RENECOFOR et la totalitĂ© des Ă©cosystĂšmes forestiers français montre des sensibilitĂ©s variĂ©es aux dĂ©pĂŽts de soufre et dâazote en fonction des Ă©cosystĂšmes, avec parmi les plus sensibles les Landes, la Sologne et le Massif Central. Des indices de qualitĂ© des habitats (HSi) ont Ă©tĂ© calculĂ©s Ă lâĂ©chelle de tous les Ă©cosystĂšmes par le modĂšle PROPS et les SDM. La sĂ©lection des espĂšces reprĂ©sentatives reste primordiale car elle conditionne la valeur finale de HSi. Ce paramĂštre est lâun des plus sensibles Ă prendre en compte dans la modĂ©lisation. Il est Ă mettre en relation avec les objectifs de protection des Ă©cosystĂšmes voulus par les gestionnaires.For decades, it has been known that atmospheric nitrogen depositions have a severe impact on the operations of forest ecosystems. Indeed, they affect the soil biogeochemistry, the balance of the nutritive elements and consequently the plant species growth, the biodiversity of the understory vegetation and more globally the forest health. As part of the Geneva Agreement to limit the long-range transboundary air pollution, the concept of "critical loads", defined towards the end of the 1980s, was adopted as a tool to enable the assessment of the sensitivity of the ecosystems to contaminants. It can be used to estimate the maximal amount of atmospheric contaminants which can be accepted by the ecosystem before significant harmful effects on specified sensitive biological indicators appear. In addition, because of the impact of global warming on biogeochemical processes regulating the functioning of ecosystems, the influence of atmospheric depositions and climate change must be considered simultaneously to evaluate the evolution of ecosystem conditions over time. Since then, the major issue has been to be able to predict the combined effect of these factors on the French forest ecosystems. This is the aim of this PhD work. Coupled dynamic biochemical-ecological models, such as ForSAFE-VEG or PROPS models, or ecological (based on EcoPlant database) were developed or adapted for this purpose and applied to different local, regional and national scales against different deposition and climatic scenarios. The application and calibration of the coupled model ForSAFE-VEG on permanent forest plots from the RENECOFOR network enabled prediction of the evolution of the soil solution biogeochemical composition, as well as monitoring of the floristic composition of three sites, under different scenarios of atmospheric deposition and climate change. The principal site evolutions are related to their stational characteristics. If the climate change plays a primary role on a speciesâ response, the oligotrophic ecosystems remain sensitive to nitrogen depositions. On a short term basis, the combined effect of the deposits and long term climate change is modulated by forest management. The extrapolation of the coupled model on a larger scale requires continuity in the availability of input data and calibration of the speciesâ response. The data and climate changes scenarios were completed and updated with the SAFRAN model and new regionalised RCP scenarios. The calibration of the response of plant species throughout France was carried out using measurements of the phytoecological database EcoPlant, via development of species distribution models (SDM). The coupling between ForSAFE and the SDM ensures a robust global modelling of the forest ecosystemsâ response over time, calibrated for the French pedoclimatic conditions. The modelling of the acidic, eutrophication and biodiversity critical loads, on all the RENECOFOR sites and French forest ecosystems, shows the various sensitivities to sulphur and nitrogen depositions depending on the ecosystem. Ecosystems located in the Landes, Sologne and Massif Central appear to be amongst the most sensitive ones. The Habitats Suitability Index (HSI) was calculated throughout all the ecosystems via PROPS models and the SDM. The selection of representative species remains pivotal as the final HSI value is conditional, depending on this factor. This parameter is one of the most sensitive factors to take into account with the model. It must be linked with forest managers' objectives for the protection of the ecosystems
How to couple ecological database to geochemical dynamic model to predict the impact of atmospheric nitrogen deposition and climate change on French forest ecosystems at the national scale?
International audienc
Atmospheric deposition measurements in France from EMEP and ICP Forest programs : Assessment of trends and ecosystem impacts
International audienc