92 research outputs found
Apport de la cartographie numĂ©rique des sols pour prĂ©dire lâhydromorphie et lâextension des zones humides potentielles Ă lâĂ©chelle rĂ©gionale
Les outils de la Cartographie NumĂ©rique des Sols (CNS) permettent de prĂ©dire des propriĂ©tĂ©s pĂ©dologiques sur de vastes Ă©tendues Ă partir dâinformations limitĂ©es sur les sols et de variables exhaustives traduisant les facteurs de formation des sols. Lâobjectif de cette Ă©tude Ă©tait dâĂ©tablir, Ă lâĂ©chelle de la rĂ©gion Bretagne, des cartes de prĂ©diction de lâhydromorphie et des zones humides par apprentissage automatique, et de les valider avec des donnĂ©es indĂ©pendantes. La premiĂšre Ă©tape a consistĂ© Ă Ă©tablir un modĂšle basĂ© sur les relationssol-environnement physique pour prĂ©dire lâhydromorphie selon 4 classes. La mĂ©thode appliquĂ©e est une classification supervisĂ©e par arbre stochastique optimisĂ©e (algorithme AdaBoost-SAMME implĂ©mentĂ© dans la boĂźte Ă outil âadabagâ du logiciel R). Le modĂšle a Ă©tĂ© calibrĂ© Ă partir de 1652 points oĂč lâhydromorphie Ă©tait connue et de 14 variables environnementales exhaustives sur la rĂ©gion, puis extrapolĂ© Ă lâensemble de la zone dâĂ©tude (27 360 kmÂČ). Dans une seconde Ă©tape, lâextension des zones humides potentielles a Ă©tĂ© dĂ©rivĂ©e de celle de lâhydromorphie par reclassement des valeurs prĂ©dites selon les critĂšres pĂ©dologiques de lâarrĂȘtĂ© du 1er octobre 2009 relatif Ă lâidentification et Ă la dĂ©limitation des zones humides. Les prĂ©dictions ont Ă©tĂ© validĂ©es Ă partir dâinformations pĂ©dologiques (donnĂ©es ponctuelles, cartes pĂ©dologiques prĂ©cises numĂ©risĂ©es et rĂ©fĂ©rentiel rĂ©gional pĂ©dologique de Bretagne Ă 1/250 000) et dâinventaires de zones humides considĂ©rĂ©s comme fiables disponibles dans le FinistĂšre.Les variables qui contribuent le plus au modĂšle de prĂ©diction de lâhydromorphie sont lâoccupation du sol, le matĂ©riau parental et la pluviomĂ©trie, suivies de la courbure verticale et de la dĂ©nivelĂ©e au cours dâeau. La prĂ©cision interne du modĂšle est satisfaisante : le taux de prĂ©dictions correctes calculĂ© Ă partir des donnĂ©es de calibration est de 77 %, lâindice de Kappa de 70 % et les 4 classes dâhydromorphie sont correctement prĂ©dites. La distribution spatiale des sols hydromorphes et des zones humides est trĂšs cohĂ©rente avec les connaissances prĂ©existantes bien que lâhydromorphie et les zones humides semblent surestimĂ©es. Cette surestimation est confirmĂ©e par la validation des rĂ©sultats du modĂšle par comparaison aux observations ponctuelles indĂ©pendantes (n =3 348) et aux cartes des sols prĂ©cises : les taux de prĂ©dictions correctes sont de 55 et 36 % respectivement, et les sols non hydromorphes sont sous-estimĂ©s.Cette Ă©tude a permis dâĂ©tablir une procĂ©dure complĂšte de prĂ©diction de lâhydromorphie et de lâextension spatiale des zones humides potentielles Ă lâĂ©chelle dâune rĂ©gion, Ă une rĂ©solution fine et assortie une incertitude. La procĂ©dure est rĂ©pĂ©table et adaptable, ce qui permet dâenvisager dâamĂ©liorer les performances du modĂšle, voire de la transposer Ă dâautres secteurs qui disposeraient de suffisamment de donnĂ©es pĂ©dologiques et de variables prĂ©dictives exhaustives
Landscape design for soil conservation under land use and climate change
International audienceSoils and landscapes evolve simultaneously. Soil evolution is controlled by redistribution and transformation processes influenced by topographic and climatic parameters, with also a major contribution of management strategies. The perennial landscape features have a strong influence on soil spatial distribution (geometry) and soil genesis. Building landscapes which enhance soil resilience to degradation processes and increase soil services appears as a promising way to adapt to forthcoming climatic and land use evolutions. The presentation aims to synthetize major results from a research program nicknamed Landsoil which focused on the evolution of agricultural soils over medium time scales (decades to centuries) in relation to changing conditions of land use and climate. Precise study of the soil 3D organization in three contrasted landscapes (Brittany, Touraine, Languedoc-Roussillon) enabled to link soil redistribution in space to landscape components (field geometry, hedges or ditches network) and their past evolution. A dynamic and high resolution spatial modeling approach was developed coupling erosion processes and soil organic matter evolution and was calibrated over past evolution using dating techniques (Cs137, C14, OSL). The resulting Landsoil model was afterwards applied in a prospective manner under different scenarios of land use and climate change over the 21th century. Indicators of soil vulnerability and soil resilience were defined and tested by the comparison of several prospective scenarios applied on a same landscape and by comparison of the contrasted landscapes
COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study
Background:
The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms.
Methods:
International, prospective observational study of 60â109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms.
Results:
âTypicalâ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (â€â18 years: 69, 48, 23; 85%), older adults (â„â70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each Pâ<â0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country.
Interpretation:
This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men
Evolution des sols Ă l'Ă©chelle du paysage sous des conditions de changements climatique et de structure du paysage.
Removal of phosphorous through roasting of oolitic iron ore with alkaline earth additives
peer reviewedThe present study is devoted to improvement of the leaching efficiency during phosphorous removal from high phosphorous gravity-magnetic concentrate. Before leaching the concentrate has been subjected to roasting with the addition of either Ca(OH)2 or CaO. The oolitic iron ore is roasted at 900°C for one hour. This reflects in reaction between alkaline earth additive and quartz, aluminosilicates, phosphorus, and some other minor components of the gangue minerals. The application of leaching, physical separation, and wash out of salts has resulted in the decrease of phosphorus from 0.7 to 0.15 % and it is established that the major influencing factor is the concentration of acid and to a less extent duration of the leaching process. About two third of the phosphorus can be removed by roasting with 3 % CaO to hematite, coarse grinding to d50 0.3 mm, dry high intensity magnetic separation and leaching of the magnetic fraction with hydro-chloric or nitric acid
Listening to earthworms burrowing and roots growing - acoustic signatures of soil biological activity
We report observations of acoustic emissions (AE) from growing plant roots and burrowing earthworms in soil, as a noninvasive method for monitoring biophysical processes that modify soil structure. AE emanating from earthworm and plants root activity were linked with time-lapse imaging in glass cells. Acoustic waveguides where installed in soil columns to monitor root growth in real time (mimicking field application). The cumulative AE events were in correlation with earthworm burrow lengths and with root growth. The number of AE events recorded from the soil columns with growing maize roots were several orders of magnitude larger than AE emanating from bare soil under similar conditions. The results suggest that AE monitoring may offer a window into largely unobservable dynamics of soil biomechanical processes such as root growth or patterns of earthworm activity - both important soil structure forming processes
RIS : RĂ©seau Imagerie des Sols
National audienceL'objectif du RĂ©seau Imagerie des Sols (RIS) est de rassembler la communautĂ© française (INRAE, mais aussi les autres instituts et universitĂ©s) travaillant sur l'imagerie des sols, quelle que soit la technique, afin dâĂ©changer sur la place que prennent aujourdâhui les travaux d'imagerie dans nos questions de recherche en science du sol. De nombreuses thĂ©matiques de recherche sont concernĂ©es : pĂ©dogĂ©nĂšse, biogĂ©ochimie dâĂ©lĂ©ments majeurs ou traces, transport dâeau et de solutĂ©s, Ă©cologie des microorganismes ou de la macrofaune, Ă©cophysiologie des racines, structure du sol, etc. Les techniques dâimagerie sont diverses (tomographie Ă rayons X ou Ă neutrons, NanoSIMS, MEB/MET, IRM, RMN 19F, ”XRF, scanner, stĂ©rĂ©omicroscopie, confocal, camĂ©ras, etc.), Ă©voluent vite, et permettent dâaccĂ©der Ă des Ă©chelles spatiales allant du nm Ă la dizaine de cm. Les images produites peuvent ĂȘtre en 2D ou en 3D, et des techniques de traitements avancĂ©es permettent aujourdâhui de corrĂ©ler des images produites par diffĂ©rents instruments pour Ă©tudier de maniĂšre intĂ©grĂ©e diffĂ©rents composants ou processus des sols. Lâimagerie permet Ă©galement dâaborder la dynamique temporelle des processus Ă©tudiĂ©s, parfois Ă des rĂ©solutions trĂšs fines grĂące Ă lâamĂ©lioration des techniques permettant des acquisitions rapides dâimages. LiĂ©es Ă lâutilisation de ces diffĂ©rentes technologies, les images acquises gĂ©nĂšrent beaucoup d'informations et des verrous scientifiques ont Ă©tĂ© identifiĂ©s pour chaque Ă©tape de la chaine dâimagerie, depuis la prĂ©paration des Ă©chantillons et l'acquisition des images, jusquâau traitement et l'exploitation de ces nombreuses donnĂ©es. FĂ©dĂ©rer les connaissances et compĂ©tences en Imagerie des Sols constitue donc un enjeu important pour une optimisation de l'utilisation de ces ressources pour tout utilisateur potentie
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