Epidemics in Networks of Spatially Correlated Three-dimensional Root Branching Structures

TL;DR

This study investigates how the complex three-dimensional structures of plant roots influence the spread of soil-borne diseases, revealing that heterogeneity and anisotropy in root morphology affect epidemic invasion thresholds.

Contribution

It introduces a novel application of bond percolation models to spatially correlated root structures, demonstrating how morphological heterogeneity impacts disease transmission.

Findings

Heterogeneities in transmissibility reduce epidemic susceptibility.

Anisotropic root shapes increase resilience to invasion.

Branching complexity enhances epidemic spread.

Abstract

Using digitized images of the three-dimensional, branching structures for root systems of bean seedlings, together with analytical and numerical methods that map a common 'SIR' epidemiological model onto the bond percolation problem, we show how the spatially-correlated branching structures of plant roots affect transmission efficiencies, and hence the invasion criterion, for a soil-borne pathogen as it spreads through ensembles of morphologically complex hosts. We conclude that the inherent heterogeneities in transmissibilities arising from correlations in the degrees of overlap between neighbouring plants, render a population of root systems less susceptible to epidemic invasion than a corresponding homogeneous system. Several components of morphological complexity are analysed that contribute to disorder and heterogeneities in transmissibility of infection. Anisotropy in root shape is shown to increase resilience to epidemic invasion, while increasing the degree of branching enhances the spread of epidemics in the population of roots. Some extension of the methods for other epidemiological systems are discussed.