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Soil water drainage is the main source of groundwater recharge and river flow. It is therefore a key process for water resource management. In this study, we evaluate the soil hydrology and the soil water drainage, simulated by the interactions between soil–biosphere–atmosphere (ISBA) land surface model currently used for hydrological applications from the watershed scale to the global scale, where parameters are generally not calibrated. This evaluation is done using seven lysimeters from two long-term model approach sites measuring hourly water dynamics between 2009 and 2019 in northeastern France. These 2 m depth lysimeters are filled with different soil types and are either maintained as bare soil or covered with vegetation. Four closed-form equations describing soil water retention and hydraulic conductivity functions are tested, namely the commonly used equations from Brooks and Corey (1966) and van Genuchten (1980), a combination of the van Genuchten (1980) soil water retention function with the Brooks and Corey (1966) unsaturated hydraulic conductivity function, and, for the very first time in a land surface model (LSM), a modified version of the van Genuchten (1980) equations, with a new hydraulic conductivity curve proposed by Iden et al. (2015). The results indicate good performance by ISBA with the different closure equations in terms of soil volumetric water content and water mass. The drained flow at the bottom of the lysimeter is well simulated, using Brooks and Corey (1966), while some weaknesses appear with van Genuchten (1980) due to the abrupt shape near the saturation of its hydraulic conductivity function. The mixed form or the new van Genuchten (1980) hydraulic conductivity function from Iden et al. (2015) allows the solving of this problem and even improves the simulation of the drainage dynamic, especially for intense drainage events. The study also highlights the importance of the vertical heterogeneity of the soil hydrodynamic parameters to correctly simulate the drainage dynamic, in addition to the primary influence of the parameters characterizing the shape of the soil water retention function.

International audience; Minerals excavated during industrial activities are stored on the soil surface, exposed to weathering, which leads to the initial development of soil. Plants contribute to soil mineral weathering, mainly by producing acidic or complexing root exudates. In addition, many plants produce antioxidant compounds and phenolic substances that could also contribute to mineral transformation processes, but have rarely been considered in relation to mineral weathering. An incubation experiment was carried out for 2 months under controlled conditions to assess the effects of antioxidant plant metabolites on the weathering processes of a clay mineral. A freshly excavated, sulphur‐rich Callovo‐Oxfordian argillite (COx) sample was artificially leached with three concentrations of three antioxidant compounds (linalool, thymol and carvacrol) or water as a control. The weathering of COx was followed by the analysis of amounts of anions and cations in the leachates. Chlorine, sulphate, nitrate, phosphate, calcium, magnesium and potassium were found in the leachates, whereas iron and aluminium were close to the detection limits. Sulphate leaching reflected oxidation of the pyritic matter contained in COx (mainly fine pyrite particles) by air. Water alone was enough to cause notable leaching of elements such as S and P, but the percentage of leached sulphate increased in the presence of two antioxidant compounds, carvacrol and thymol, and increased to 38% with thymol at 2 mg l−1 compared with the antioxidant‐free control. Thus, antioxidant compounds could contribute to the leaching of elements from COx, depending on their nature and concentration.

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International audience; The physicochemical properties of forest soils affect every aspect of soil fertility and productivity. Soil properties notably determine the availability of nutrients and water, and the ease of their absorption by trees, the ease of root penetration, and the degree to which solution moves both laterally and vertically through the soil. In consequence, soil properties can strongly influence tree nutrition and forest productivity. However, trees have at their disposal several mechanisms to improve nutrient availability in low-nutrient environments, i.e., modification of root architecture and exudation, association with microorganisms... This work aims at determining the impact of soil properties and root distribution on forest current productivity. In this view, the forest of Montiers (North East of France) was chosen to support the study because it presents a great diversity of soils representative of the French temperate forest on which rests a mature beech forest stand (50 year-old). In june 2009, 27 soil profiles were sampled in the rendisol, in the calci-brunisol and in the alocrisol for a total of 81 soil profiles. The physico-chemical properties and the root density were measured in these profiles. In addition, the trunk circumferences at breast level and the height were measured in 2009 and 2013 on about 2500 trees distributed on the three soils. By way of modeling, the biomass in the different tree compartments (0 to 4, 4 to 7 and > 7 cm diameter branches, trunk bark and wood) was determined for both dates. This work will present for the three soils (i) the soil physico-chemical properties, i.e., pH, base saturation, particle size distribution, soil water holding capacity and C, N and nutrient stocks, (ii) the evolution of the tree biomass, and (iii) the root density in the different soil horizons. The relations between soil fertility, forest productivity and soil root colonization are discussed.

International audience; Forests provide many benefits and services to society, including clean water, recreation, wildlife habitat, carbon storage, and a variety of forest products. Because nutrient availability is a major driver of forest stability, intensification of wood exportation and notably small woods (nutrient-rich organs) for bio-energy, threatens forest soil fertility and in consequence ecosystem functioning. Maintaining the management of forests in a sustainable way, while adapting to global change is a big challenge. Here, we use field and modeling studies to assess the relative sensitivity of different types of soils face to increase of biomass exportation in a beech mature forest of the North East of France. The study site with a surface area of 252 km2 is characterized by a great diversity of soils representative of the region, i.e., rendosol, rendisol, calcisol, brunisols, and alocrisols. To achieve this objective, we used a combination of field measurements of soil properties and a mass balance modeling of nutrient dynamics in soils. In this study, we clearly demonstrated that intensification of biomass exportation (wood-energy practice) may drastically reduce soil mineral fertility, even in soils reputed to be nutrient-rich, leading in term to nutrient deficiencies (mainly phosphorus and potassium), and to stand decline for most of the studied soils. In consequence, the choice of forest management (level of biomass exportation, species...) must be reasoned in adequacy with the available soil resources in nutrients, which depends on soil properties. These strategies appear to be more important in a context of global change.

International audience

Accumulation of trace metals, such as cadmium (Cd), in soils and their transfer to plants are serious environmental problems because of their acute toxicity. Metal mobility in soil depends on various abiotic and biotic factors. Among them, arbuscular mycorrhizal (AM) fungi are known to influence metal transfer by transporting metals to roots and also by improving plant growth. However, diverging results were reported and the global role of AM fungi thus needed more investigation. The influence of an AM fungus (Glomus intraradices) on Cd uptake and transfer to leachates was studied with Medicago truncatula as a host plant. Experiments were performed in pot cultures and in compartmented devices. The dynamic of Cd in the soil-plant system was indirectly influenced by the fungus via a strong increase of plant biomass, in interaction with nodulating rhizobacteria, leading to a higher total quantity of Cd transferred to shoots although Cd plant concentration was lower than in non mycorrhizal plants. This fungal influence was complex, and was variable according to soil conditions and to the fungal isolate studied. The AM fungus also contributed directly to Cd transfer thanks to its sorption capacity and its ability to transport soluble-exchangeable Cd via the extraradical mycelium, but this direct contribution seemed to be low as compared to the influence of roots.; L'accumulation d'éléments en traces métalliques (ETM), dont le cadmium (Cd), dans les sols et leur transfert aux plantes sont problématiques à cause de leur toxicité. Les champignons mycorhiziens à arbuscules (MA), symbiontes des plantes, peuvent influencer le transfert des ETM de manière directe en les transportant jusqu'aux racines et de manière indirecte en favorisant la croissance de la plante. Des résultats divergents ont néanmoins été reportés et leur rôle global doit donc être éclairci. En prenant comme plante modèle la luzerne Medicago truncatula, l'effet d'un champignon MA (Glomus intraradices) sur le bilan de Cd dans la plante, le sol et les percolats a été étudié. La contribution du champignon au transfert de Cd a été évaluée dans des cultures en pot et des dispositifs à compartiment. Le champignon a principalement influencé la dynamique de Cd dans le système sol-plante de manière indirecte en améliorant fortement la croissance de la plante sur sol contaminé, conduisant à une quantité plus importante de Cd exporté dans les parties aériennes de la plante, bien que leur concentration en Cd soit plus faible que dans les plantes non mycorhizées. Cette forte augmentation de croissance de la luzerne par ce champignon est associée à la stimulation de bactéries formant des nodules. Cette influence mycorhizienne est néanmoins complexe, elle est variable selon les conditions édaphiques et selon l'isolat du champignon étudié. Le champignon MA contribue aussi directement au transfert de Cd en sorbant et en transportant le Cd soluble-échangeable par son mycélium extraracinaire, mais cette contribution directe semble être faible en comparaison de l'effet des racines.

Accumulation of trace metals, such as cadmium (Cd), in soils and their transfer to plants are serious environmental problems because of their acute toxicity. Metal mobility in soil depends on various abiotic and biotic factors. Among them, arbuscular mycorrhizal (AM) fungi are known to influence metal transfer by transporting metals to roots and also by improving plant growth. However, diverging results were reported and the global role of AM fungi thus needed more investigation. The influence of an AM fungus (Glomus intraradices) on Cd uptake and transfer to leachates was studied with Medicago truncatula as a host plant. Experiments were performed in pot cultures and in compartmented devices. The dynamic of Cd in the soil-plant system was indirectly influenced by the fungus via a strong increase of plant biomass, in interaction with nodulating rhizobacteria, leading to a higher total quantity of Cd transferred to shoots although Cd plant concentration was lower than in non mycorrhizal plants. This fungal influence was complex, and was variable according to soil conditions and to the fungal isolate studied. The AM fungus also contributed directly to Cd transfer thanks to its sorption capacity and its ability to transport soluble-exchangeable Cd via the extraradical mycelium, but this direct contribution seemed to be low as compared to the influence of roots.; L'accumulation d'éléments en traces métalliques (ETM), dont le cadmium (Cd), dans les sols et leur transfert aux plantes sont problématiques à cause de leur toxicité. Les champignons mycorhiziens à arbuscules (MA), symbiontes des plantes, peuvent influencer le transfert des ETM de manière directe en les transportant jusqu'aux racines et de manière indirecte en favorisant la croissance de la plante. Des résultats divergents ont néanmoins été reportés et leur rôle global doit donc être éclairci. En prenant comme plante modèle la luzerne Medicago truncatula, l'effet d'un champignon MA (Glomus intraradices) sur le bilan de Cd dans la plante, le sol et les percolats a été étudié. La contribution du champignon au transfert de Cd a été évaluée dans des cultures en pot et des dispositifs à compartiment. Le champignon a principalement influencé la dynamique de Cd dans le système sol-plante de manière indirecte en améliorant fortement la croissance de la plante sur sol contaminé, conduisant à une quantité plus importante de Cd exporté dans les parties aériennes de la plante, bien que leur concentration en Cd soit plus faible que dans les plantes non mycorhizées. Cette forte augmentation de croissance de la luzerne par ce champignon est associée à la stimulation de bactéries formant des nodules. Cette influence mycorhizienne est néanmoins complexe, elle est variable selon les conditions édaphiques et selon l'isolat du champignon étudié. Le champignon MA contribue aussi directement au transfert de Cd en sorbant et en transportant le Cd soluble-échangeable par son mycélium extraracinaire, mais cette contribution directe semble être faible en comparaison de l'effet des racines.