Simulating water uptake in the root zone with a microscopic-scale model of root extraction

Abstract

Root water uptake is a key element for analysing the evolution of soil water content, which regulates crop transpiration. Our objective was to design a model taking into account the vertical water redistribution and the root water uptake in order to assess the regulation of plant transpiration induced by the effective soil water availability. To do so, the root water uptake is described with a microscopic-scale model integrated within a classical model of vertical water redistribution. For root water uptake, the root water potential, leading the water transfer from soil to roots, is calculated in order to satisfy the climatic demand... By coupling the microscopic and macroscopic approaches to soil water transfer, the regulation of transpiration can be directly linked to soil hydraulic properties and to effective soil water availability: the numerical model is applied to simulate soil water movement with root water uptake, and simulation results are compared with a series of findings on plant functioning obtained by previous work. Qualitatively, simulated transpiration in response to the soil water content is reasonably consistent with the description of crop behaviour in drying soils and in soil with vertical water heterogeneity. The results are also compared with experimental results in order to evaluate the usefulness of this model: with conventional measurements under field conditions, the prediction of water balance evolution is rather consistent with experimental results. model / root water uptake / soil-root transfer / transpiration / water Résumé-Simulation du prélèvement racinaire sur l'ensemble du système racinaire. Le prélèvement racinaire d'eau par les plantes est le point-clé pour l'analyse de l'évolution du contenu en eau du sol, lequel régule la transpiration des cultures. Notre objectif est de concevoir un modèle qui prenne en compte à la fois la redistribution verticale de l'eau dans le sol et à la fois le prélèvement racinaire pour évaluer les régulations de la plante induites par la disponibilité de l'eau du sol. Pour cela, le prélèvement racinaire qui est évalué par un modèle d'extraction racinaire décrivant les transferts sol-racine à l'échelle microscopique est couplé à un modèle de redistribution verticale de l'eau dans le sol. Grâce à ce couplage entre une approche microscopique et une approche macroscopique, la régulation de la transpiration est directement reliée aux propriétés de transfert d'eau du sol et à la disponibilité effective de l'eau pour le système racinaire. Les résultats des simulations sont mis en parallèle avec un ensemble de résultats expérimentaux caractérisant les réponses des plantes à une phase de dessèchement du sol. Qualitativement, les comportements de la plante vus sous l'angle de l'eau sont reproduits de manière satisfaisante pour un sol s'asséchant et pour un sol ayant un profl vertical d'humidité hétérogène. Les résultats du modèle sont également comparés avec des résultats expérimentaux obtenus dans les conditions naturelles. A partir de mesures classiques réal...

Impact of active transport and transpiration on nickel and cadmium accumulation in the leaves of the Ni-hyperaccumulator Leptoplax emarginata: a biophysical approach

“…Similarly, the gradient of ψ around roots is small in the case of soils with large K(θ), such as potting composts, sand or vermiculite (Jones and Tardieu 1998;Personne et al 2003). Moreover, similarly to this study, Carminati et al (2010) recently found no gradients of water content in the lupin-sandy soil rhizosphere after a drying period (but an increase of θ towards the roots after soil rewetting), water content distributions being recorded by non-destructive neutron radiography.…”

An optimality-based model of the coupled soil moisture and root dynamics

“…The latter corresponds to previous approaches to modelling HR (e.g. Amenu and Kumar, 2007;Personne et al, 2003), while modelling drought-avoiding roots in a hydrological model has not been done before to our knowledge. The better reproduction of observations by the optimisation-based model suggests that drought-avoiding roots dominate in the investigated savanna, but it does not allow conclusions about the generality of such a strategy.…”

Mechanisms of vegetation uprooting by flow in alluvial non-cohesive sediment

“…The latter has recently been modelled (Laio, 2006) using a stochastic approach to describe the water balance of a horizontal soil layer of infinitesimal thickness (e.g., Lai and Katul, 2000) in the presence of a vertical density distribution of roots and relating root uptake to evapotranspiration rate. The latter choice for water and nutrients uptake by roots is in accordance with some of the most common uptake models existing in literature (e.g., Feddes et al, 2001;Sperry et al, 2002), although more detailed approaches are available (Itoh and Barber, 1983;Personne et al, 2003;Roose and Fowler, 2004). On that basis a first step towards describing the root and soil moisture inter-adjustments (i.e., hydrotropism) has been proposed by Schenk (2005) and Laio (2006).…”

“…More recently, the active role of vegetation has been considered (e.g. see Gurnell and Petts, 2002;Gurnell et at, 2001;Steiger et al, 2003;Perona et al, 2008Perona et al, , 2009b) and coupled to the equations of morphodynamics in order to better explain the role that riparian vegetation play when colonizing point bars (Perucca et al, 2007) as well as the reciprocal interactions with river hydrology as a Markov process with dichotomic noise at both the transect and corridor scales (Perona et al, 2009a;Muneepeerakul et al, 2007). Gran and Paola (2001) used Alfalfa grass to study the effect of vegetation on a braided stream under steady flow conditions.…”