Leaf dispersion and light partitioning in three-dimensionally digitized tall fescue-white clover mixtures

Abstract

A three-dimensional digitizing method was used to assess the canopy structure of six Festuca arundinacea (FA)-Trifolium repens (TR) mixtures during the installation stage. Virtual canopy images were synthesized and used to derive light interception and partitioning between species. Computations from images were compared with a simple light model based on Beer's law, in order to analyse within- and between-species foliage dispersion. The total leaf area index of the mixtures ranged from 0.6 to 4.5. The fraction of FA foliage overtopping TR was 9-30%. The mean inclination of FA and TR was 66 and 57°, respectively. Within-species dispersion parameters of FA and TR were about 0.8 and 1.0, namely clumped and random foliage dispersion, respectively. Although FA was sown in rows, between-species dispersion was random. Lower leaf inclination and lesser clumping in TR compensated foliage overtopping by FA, so that light partitioning between FA and TR (about 80 and 20%, respectively) was similar to the species contribution to total canopy foliage. Since between-species dispersion was random, a simple two-layer light model based on Beer's law provided correct estimations of light partitioning (RMSE = 0.05), although light interception by FA was slightly overestimated because of its clumped dispersion.