Analyzing Root Competition with Dirichlet Tessellation for Wheat on Three Landscape Positions

Abstract

AbstractThe underlying mechanisms for root competition are not completely understood; yet, it is important to accurately define the zone of influence around individual roots for nutrient or water uptake, particularly when modeling nutrient uptake processes. The objectives of this study were to investigate the use of the Dirichlet tessellation for quantifying soil polygons around roots of spring wheat (Triticum aestivum L. cv. Katepwa) grown on three landscape positions and to quantify the root spatial patterns. Roots were exposed on a horizontal soil plane at 2‐, 5‐, and 10‐cm depths and mapped on acetate sheets at 21, 45, and 88 days after planting (DAP) for shoulder, backslope, and footslope positions. Tessellation of scanned root maps showed that soil polygons decreased in size during the sampling period; however, polygon areas increased with soil depth regardless of slope position and ranged from 0.08 to 52.77 cm2. Eccentricity averaged 0.74 ± 0.01, indicating that polygons were more circular than elliptical and root displacement averaged one‐third the distance from the polygon center to the polygon edge. Root spatial patterns using R‐index values, showed that roots on shoulder positions had clumped to random patterns while roots at the footslope had random to regular patterns. Root spatial patterns and displacement for wheat violated the assumptions used in nutrient uptake modeling and should be incorporated into future modeling efforts. Dirichlet tessellation is an effective procedure for analyzing root competition and has promise for multispecies competition if different root systems can be weighted by morphological or physiological characteristics.