A fractal root model applied for estimating the root biomass and architecture in two tropical legume tree species

Abstract

A fractal root model with parameter estimation based on pipe model theory was applied for studying root architecture of Erythrina lanceolata and Gliricidia sepium associated with crops in agroforestry. The results were compared with a theoretical volume-filling fractal model on scaling of plant vascular system. Scaling of root diameter at bifurcation followed same parameter values over the whole root system. The parameter values were approximately equal in both species. Length between two bifurcations could not be estimated according to volume-filling fractal principles, but an empirical regression was used. An empirical model was also applied for estimating bifurcation angles. These characteristics seem to respond strongly to local root environment, and their modelling calls for studying root-soil interactions. Agronomic applications of this study indicate the usefulness of an architectural approach for the study of belowground interactions in agroforestry systems.