Proposition of a Conceptual Density Based Model to Describe Fine Root Networks in Tree Root Systems

Describing tree root systems development, i.e. spatiotemporal variation of topological, geometrical or functional parameters, is necessary in many application fields. In particular rooting data as Root Area Ratio (RAR) or root length density have to be considered in eco-engineering models that aim in quantifying the influence of vegetation on the increase in soil cohesion and prevention of soil erosion and landslides. It is usually distinguished between coarse roots that play a mechanical role in plant anchorage and fine roots that play a role in water and nutrient uptake. This paper proposes a new mixed modelling approach dedicated to the simulation of tree root growth and considering these two root types. Whereas the coarse root structure is assumed to be known, fine roots are simulated using a density based model expressed under the form of partial differential equations and based on Bastian et al. model. This last aggregated model integrates morphological and functional traits, e.g. branching and elongation functions. Numerical results and analysis of the model parameters are shown considering one fine root source and then a simple root structure with two fine root sources competing each other for space.