Estimating PAR transmittance of individual trees using multi-return airborne LiDAR and radiative transfer simulation

In this study we demonstrate a method for estimating the photosynthetically active radiation (PAR) transmittance of individual trees in an urban district. The leaf area density (LAD) distribution, derived from airborne light detection and ranging (LiDAR) data using a method proposed by our previous study, is applied to radiative transfer simulation of vegetation. Estimation accuracy of the PAR transmittance is verified using a single broad-leaved tree. The PAR distribution under a Zelkova tree is measured by a device that consists of 1 m probe, in which 64 PAR sensors are distributed. The estimated transmittance is then compared with the measured one. We conclude that when the derived LAD distribution is used, PAR transmittance is estimated within an error of 0.06, regardless of solar altitude. The influence of airborne LiDAR observation specification and method for deriving LAD distribution on the estimation accuracy of PAR transmittance is also examined.