Optical Diffraction Analysis for Estimating Foliage Angle Distribution in Grassland Canopies

Abstract

A non-destructive, rapid technique utilizing horizontal in situ ground photographs for estimating foliage angle distributions is discussed. Optical diffraction patterns generated from orthogonal photographs are analysed for angular bias by wedge sampling. Probability distributions for planar projections of foliage orientations are derived from these measurements and mathematically convo- luted to determine the actual three-space probability distribution function for foliage angles. The method is particularly appropriate for dense canopies which are difficult to measure by other tech- niques. The diffraction technique is evaluated for abstract canopies and for a canopy of Western wheat grass (Agropyron smithii). It also yields physically consistent interpretations for the phenolo- gical development of domestic Satanta wheat (Triticum aestivum).