Variabilité spatiale de la minéralisation de substrats carbonés (2,4-D, leucine, lysine) dans la matrice solide du sol

La matrice du sol, par l'intermédiaire de sa texture et de sa structure, est à l'origine d'une hétérogénéité spatiale de la matière organique et des microorganismes. Elle peut favoriser ou non la biodégradation en contrôlant d'une part l'accessibilité et la disponibilité des molécules carbonées pour les microorganismes et d'autre part les conditions environnementales locales (disponibilité en O2, H2O ). Toutefois, ces phénomènes sont mal connus, ce qui limite particulièrement la prévision de la dynamique des composés organiques dans les sols. La difficulté majeure vient de l'hétérogénéité des caractéristiques du sol à l'échelle des agrégats et tout particulièrement celle de l'activité des microorganismes dégradants à cette échelle, et de la grande diversité des paramètres impliqués (nature des matières organiques, texture, porosité ). L'objectif de ces travaux était donc d'étudier la variabilité spatiale de la minéralisation par les microorganismes dans la matrice solide du sol. Trois substrats carbonés ont été choisis, le 2,4-D, la leucine et la lysine, différents par la taille de leur microflore dégradante et leur propriété d'adsorption sur le sol. La minéralisation de ces substrats est d'autant plus hétérogène spatialement que l'échelle est fine (échelle millimétrique à décamétrique) et varie également en fonction des propriétés des substrats. Les coefficients de variation maximum de la minéralisation du 2,4-D entre agrégats individuels (échelle millimétrique) varient entre 40 et 70% (entre 10 et 30% pour les acides aminés) selon la classe de taille d'agrégats considérée (2-3.15, 3.15-5 ou 5-7 mm) alors qu'ils ne sont plus que de 20 à 30% à l'échelle métrique et de 15% à l'échelle décamétrique. En outre, à l'échelle millimétrique, l'hétérogénéité spatiale de la minéralisation s'explique par une distribution hétérogène des microorganismes dégradants et du C disponible et s'organise sous forme de hot spots centimétriques. Enfin, la localisation initiale du substrat peut affecter la minéralisation lorsque ce dernier est concentré sur un faible nombre d'agrégats (les différences maximales entre un apport du substrat le plus concentré et un apport du substrat homogène étant de 6.5% du 14C apporté dans le cas du 2,4-D et de 10% du 14C apporté pour les acides aminés), probablement à cause d'un rapport substrat / microorganismes plus élevé localement plutôt qu'à des problèmes d'accessibilité du substrat pour les microorganismesLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Variability of pesticide mineralization in individual soil aggregates of millimeter size

International audienc

Heterogeneity of pesticide mineralisation among individual soil aggregates of millimetre size

*INRA Science du Sol 78026 Versailles (FRA) Diffusion du document : INRA Science du Sol 78026 Versailles (FRA)International audienc

BD : Pourquoi mettre des fermes dans les villes ?

https://theconversation.com/bd-pourquoi-mettre-des-fermes-dans-les-villes-142107Objet de recherche récent pour les scientifiques, les microfermes urbaines sont aujourd’hui en plein essor, portées par un mouvement associatif, citoyen, entrepreneurial et politique relativement important.Ces lieux associent différentes activités : projets éducatifs, production alimentaire, loisirs, etc. Ils constituent au cœur des villes des espaces végétalisés d’un nouveau type, susceptibles de fournir de multiples services écosystémiques (soit les avantages que la nature apporte à la société).Mais le manque de connaissances actuel ne permet pas d’appréhender précisément l’importance de ces services.Dans notre reportage BD, vous découvrirez cette forme étonnante d’agriculture en suivant les travaux du programme de recherche « SEMOIRS » qui a étudié deux années durant les services écosystémiques rendus par six microfermes dans Paris et sa petite couronne

Soilμ3d project: emergent properties of soil microbial functions from 3d modelling and spatial descriptors of pore scale heterogeneity

International audienceThe reduction of greenhouse gas emissions by improving the efficiency of agricultural systems through robust ecologically-based management practices represents the most important challenge facing agriculture. Models are needed to evaluate the effects of soil properties, climate, and agricultural management practices on soil carbon and on the nitrogen transformations responsible for GHG emissions. Models of Carbon and nitrogen cycles in soils need improvements so they can provide more accurate and robust predictions. They use empirical functions which account for the different environmental factors that affect microbial functions. However, these types of function have limitations because they don’t consider the micro heterogeneity of soil at the scale of microorganisms and they cannot describe processes that are connected to each other by complex interactions linked to soil structure. Mechanistic representation of small-scale processes was identified in literature as one of the priorities to improve these global soil organic matter dynamics models.Our previous project showed the importance of the habitat of soil microorganisms, and especially how physical characteristics (pore sizes, connectivity) control the decomposition of organic substrates via experimental microcosm. We have developed a suite of methods and models to visualize in 2D or 3D soil heterogeneity at scales relevant for microorganisms. It has also contributed to the development of three very complementary 3D models able to simulate for the first time the microbial degradation of organic matter at the scale of microhabitats in soil using real 3D images of soils. The goal of this Soilµ3D project is now to go further by using the 3D models resulting from MEPSOM to upscale heterogeneities identified at the scale of microhabitats to the soil profile scale. The aims of the project are to: develop new descriptors of the pore scale 3D soil heterogeneity that explain the fluxes measured at the core scale, use our 3D models to connect the µ-scale heterogeneity and the measured macroscale fluxes, develop new simple models describing the soil micro-heterogeneity and integrating these micro-features into field-scale models.Several improvements have been made to 3D models, such as: i) model parallelization, ii) more compact representation of pore space by ellipsoids as geometric primitives, iii) coupling with Individual based models. Two Literature reviews were written concerning technics of 3D images at small scale (Baveye et al, 2018) and the 3D modelling of soil pores microscopic architecture (Pot et al., 2020) .Modeling scenarios from 3D soil images has shown the importance of the connectivity of water-filled pores in carbon mineralization. The number of clusters of pores filled with water appears to be a relevant indicator of CO2 emissions. This modeling shows that the diffusion of the 3D substrate controls the contact between µorganisms and organic matter and therefore the rates of decomposition. A threshold effect is observed with an increase in the decomposition of organic matter when low substrate concentrations are associated with a high number of bacterial cells compared to a population model

Soilμ3d project: emergent properties of soil microbial functions from 3d modelling and spatial descriptors of pore scale heterogeneity

International audienceThe reduction of greenhouse gas emissions by improving the efficiency of agricultural systems through robust ecologically-based management practices represents the most important challenge facing agriculture. Models are needed to evaluate the effects of soil properties, climate, and agricultural management practices on soil carbon and on the nitrogen transformations responsible for GHG emissions. Models of Carbon and nitrogen cycles in soils need improvements so they can provide more accurate and robust predictions. They use empirical functions which account for the different environmental factors that affect microbial functions. However, these types of function have limitations because they don’t consider the micro heterogeneity of soil at the scale of microorganisms and they cannot describe processes that are connected to each other by complex interactions linked to soil structure. Mechanistic representation of small-scale processes was identified in literature as one of the priorities to improve these global soil organic matter dynamics models.Our previous project showed the importance of the habitat of soil microorganisms, and especially how physical characteristics (pore sizes, connectivity) control the decomposition of organic substrates via experimental microcosm. We have developed a suite of methods and models to visualize in 2D or 3D soil heterogeneity at scales relevant for microorganisms. It has also contributed to the development of three very complementary 3D models able to simulate for the first time the microbial degradation of organic matter at the scale of microhabitats in soil using real 3D images of soils. The goal of this Soilµ3D project is now to go further by using the 3D models resulting from MEPSOM to upscale heterogeneities identified at the scale of microhabitats to the soil profile scale. The aims of the project are to: develop new descriptors of the pore scale 3D soil heterogeneity that explain the fluxes measured at the core scale, use our 3D models to connect the µ-scale heterogeneity and the measured macroscale fluxes, develop new simple models describing the soil micro-heterogeneity and integrating these micro-features into field-scale models.Several improvements have been made to 3D models, such as: i) model parallelization, ii) more compact representation of pore space by ellipsoids as geometric primitives, iii) coupling with Individual based models. Two Literature reviews were written concerning technics of 3D images at small scale (Baveye et al, 2018) and the 3D modelling of soil pores microscopic architecture (Pot et al., 2020) .Modeling scenarios from 3D soil images has shown the importance of the connectivity of water-filled pores in carbon mineralization. The number of clusters of pores filled with water appears to be a relevant indicator of CO2 emissions. This modeling shows that the diffusion of the 3D substrate controls the contact between µorganisms and organic matter and therefore the rates of decomposition. A threshold effect is observed with an increase in the decomposition of organic matter when low substrate concentrations are associated with a high number of bacterial cells compared to a population model

Soilμ3d project: emergent properties of soil microbial functions from 3d modelling and spatial descriptors of pore scale heterogeneity

International audienceThe reduction of greenhouse gas emissions by improving the efficiency of agricultural systems through robust ecologically-based management practices represents the most important challenge facing agriculture. Models are needed to evaluate the effects of soil properties, climate, and agricultural management practices on soil carbon and on the nitrogen transformations responsible for GHG emissions. Models of Carbon and nitrogen cycles in soils need improvements so they can provide more accurate and robust predictions. They use empirical functions which account for the different environmental factors that affect microbial functions. However, these types of function have limitations because they don’t consider the micro heterogeneity of soil at the scale of microorganisms and they cannot describe processes that are connected to each other by complex interactions linked to soil structure. Mechanistic representation of small-scale processes was identified in literature as one of the priorities to improve these global soil organic matter dynamics models.Our previous project showed the importance of the habitat of soil microorganisms, and especially how physical characteristics (pore sizes, connectivity) control the decomposition of organic substrates via experimental microcosm. We have developed a suite of methods and models to visualize in 2D or 3D soil heterogeneity at scales relevant for microorganisms. It has also contributed to the development of three very complementary 3D models able to simulate for the first time the microbial degradation of organic matter at the scale of microhabitats in soil using real 3D images of soils. The goal of this Soilµ3D project is now to go further by using the 3D models resulting from MEPSOM to upscale heterogeneities identified at the scale of microhabitats to the soil profile scale. The aims of the project are to: develop new descriptors of the pore scale 3D soil heterogeneity that explain the fluxes measured at the core scale, use our 3D models to connect the µ-scale heterogeneity and the measured macroscale fluxes, develop new simple models describing the soil micro-heterogeneity and integrating these micro-features into field-scale models.Several improvements have been made to 3D models, such as: i) model parallelization, ii) more compact representation of pore space by ellipsoids as geometric primitives, iii) coupling with Individual based models. Two Literature reviews were written concerning technics of 3D images at small scale (Baveye et al, 2018) and the 3D modelling of soil pores microscopic architecture (Pot et al., 2020) .Modeling scenarios from 3D soil images has shown the importance of the connectivity of water-filled pores in carbon mineralization. The number of clusters of pores filled with water appears to be a relevant indicator of CO2 emissions. This modeling shows that the diffusion of the 3D substrate controls the contact between µorganisms and organic matter and therefore the rates of decomposition. A threshold effect is observed with an increase in the decomposition of organic matter when low substrate concentrations are associated with a high number of bacterial cells compared to a population model

Soilμ3d project: emergent properties of soil microbial functions from 3d modelling and spatial descriptors of pore scale heterogeneity

International audienceThe reduction of greenhouse gas emissions by improving the efficiency of agricultural systems through robust ecologically-based management practices represents the most important challenge facing agriculture. Models are needed to evaluate the effects of soil properties, climate, and agricultural management practices on soil carbon and on the nitrogen transformations responsible for GHG emissions. Models of Carbon and nitrogen cycles in soils need improvements so they can provide more accurate and robust predictions. They use empirical functions which account for the different environmental factors that affect microbial functions. However, these types of function have limitations because they don’t consider the micro heterogeneity of soil at the scale of microorganisms and they cannot describe processes that are connected to each other by complex interactions linked to soil structure. Mechanistic representation of small-scale processes was identified in literature as one of the priorities to improve these global soil organic matter dynamics models.Our previous project showed the importance of the habitat of soil microorganisms, and especially how physical characteristics (pore sizes, connectivity) control the decomposition of organic substrates via experimental microcosm. We have developed a suite of methods and models to visualize in 2D or 3D soil heterogeneity at scales relevant for microorganisms. It has also contributed to the development of three very complementary 3D models able to simulate for the first time the microbial degradation of organic matter at the scale of microhabitats in soil using real 3D images of soils. The goal of this Soilµ3D project is now to go further by using the 3D models resulting from MEPSOM to upscale heterogeneities identified at the scale of microhabitats to the soil profile scale. The aims of the project are to: develop new descriptors of the pore scale 3D soil heterogeneity that explain the fluxes measured at the core scale, use our 3D models to connect the µ-scale heterogeneity and the measured macroscale fluxes, develop new simple models describing the soil micro-heterogeneity and integrating these micro-features into field-scale models.Several improvements have been made to 3D models, such as: i) model parallelization, ii) more compact representation of pore space by ellipsoids as geometric primitives, iii) coupling with Individual based models. Two Literature reviews were written concerning technics of 3D images at small scale (Baveye et al, 2018) and the 3D modelling of soil pores microscopic architecture (Pot et al., 2020) .Modeling scenarios from 3D soil images has shown the importance of the connectivity of water-filled pores in carbon mineralization. The number of clusters of pores filled with water appears to be a relevant indicator of CO2 emissions. This modeling shows that the diffusion of the 3D substrate controls the contact between µorganisms and organic matter and therefore the rates of decomposition. A threshold effect is observed with an increase in the decomposition of organic matter when low substrate concentrations are associated with a high number of bacterial cells compared to a population model

Hétérogénéités spatiales générées par l'enfouissement de produits résiduaires organiques à l'échelle du profil cultural: impacts sur la dynamique des micropolluants organiques et minéraux

National audienc