Plant roots; Agrogeophysics; electrical signature of roots
Abstract :
[en] The application of geophysical methods to cropped fields has been increasing in recent years because of the limitations associated with the use of traditional methods (root excavation, monoliths and minirhizotron studies etc.) due to the spatiotemporal variability and dynamics within the root zone. Geophysical methods address these limitations by offering high resolution and non-invasive approaches to root investigation due to their ability to map properties and structures as well as flow and transport processes in the shallow subsurface. Among the available geophysical methods both electrical resistivity or impedance tomography (ERT/EIT) hold a promising future for root system and root water uptake characterization. Despite significant improvements in the past years, there is still a knowledge gap (1) at the segment scale regarding the electrical response of roots, which is essential to account for the effect of roots in the estimation of soil moisture content of rooted soils or to exploit geophysical methods to characterize certain root system traits, and (2) at the root system scale to account for the full root architecture in a heterogeneous soil when intending to estimate root water uptake. Here, we measured electrical properties of single root segments of different plants (Maize and Brachypodium) from 1 Hz -to 45 kHz using a specific sample holder designed for root segments. We then used these electrical properties in a numerical electrical model coupled with a plant-soil water flow model to investigate the impact of plant root growth and water uptake in a virtual ERT experiment. The roots were explicitly represented with their electrical properties for varying soil conditions. Modeling results indicate non-negligible, soil-type dependent anisotropy in bulk electrical conductivity induced by the given root distribution. When root-soil electrical conductivity contrasts are high, our virtual experiments show that disregarding the contribution of roots to the electrical resistivity at the segment scale can lead to inaccurate water content estimates at the root system scale.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Nguyen, Frédéric ; Université de Liège - ULiège > Département ArGEnCo > Géophysique appliquée
Rao, Sathyanarayan; Université Catholique de Louvain - UCL > ELI