A comparative assessment of the vertical distribution of forest components using full-waveform airborne, discrete airborne and discrete terrestrial laser scanning data

•The reliability of vegetation density estimates is determined by signal occlusion.•Vertical profiles from full-waveform ALS are more similar to those from TLS.•Full-waveform ALS determines understory density more accurately than discrete ALS.•Discrete ALS may be used to determine understory vegetation density at plot-level.•Gini index determines understory vegetation density from ALS vertical profiles.