Seeking stable traits to characterize the root system architecture. Study on 60 species located at two sites in natura.

Abstract

In several disciplines, identifying relevant root traits to characterize the root system architecture of species or genotypes is a crucial step. To address this question, we analysed the inter-specific variations of root architectural traits in two contrasting environments. We sampled 60 species in natura, at two sites, each presenting homogeneous soil conditions. We estimated for each species and site a set of five traits used for the modelling of the root system architecture: extreme tip diameters (Dmin and Dmax), relative diameter range (Drange), mean inter-branch distance (IBD) and dominance slope between the diameters of parent and lateral roots (DlDm). The five traits presented a highly significant species effect, explaining between 77 and 98 % of the total variation. Dmin, Dmax and Drange were particularly determined by the species, while DlDm and IBD exhibited a higher percentage of environmental variations. These traits make it possible to confirm two main axes of variation: 'fineness-density' (defined by Dmin and IBD) and 'dominance-heterorhizy' (DlDm and Drange), that together accounted for 84 % of the variations observed. We confirmed the interest of these traits in the characterization of the root system architecture in ecology and genetics, and suggest using them to enrich the 'root economic spectrum'.