Comparison of Terrestrial and Airborne LiDAR in Describing Stand Structure of a Thinned lodgepole Pine Forest

Airborne LiDAR (ALS) has been widely used for measuring canopy structure, but much of the woody components of the canopy are not directly visible with this system. Terrestrial LiDAR (TLS) data may help fill this gap by helping to understand the relationship between above- and below-canopy architecture. In this study, we report on the potential for combining TLS and ALS, thereby focusing on forest inventory and wood quality related characteristics (such as number and dimension of branches). Our results show that both TLS and ALS were able to describe stand height using the top 10% of LiDAR returns at a high level of precision; however, TLS measurements were negatively biased by approximately 1 m (R-2 = 0.96 and 0.86 for ALS and TLS, respectively; P < 0.05). The distribution of foliage measured by ALS and TLS was strongly related to basal area (R-2 = 0.63 and 0.91 for ALS and TLS, respectively) and stand density (R-2 = 0.89 and 0.72 for ALS and TLS, respectively). Tree-level attributes were more accurately described by TLS (R-2 = 0.63) compared with ALS (R-2 = 0.37) for crown depth and a similar result applied to dbh with R-2 = 0.63 for TLS versus R-2 = 0.43 for ALS.