Forest Canopy Leaf Area Density Estimation Based on Airborne and Terrestrial Lidar Data

Abstract

The leaf area density (LAD) plays an important role in describing the vertical canopy structure. Light Detection and Ranging (LiDAR) is an active remote-sensing technology that has already been applied to canopy measurements. In this paper, the vertical profiles of the LAD of three different size plots $(15 \mathrm{x} 15 \mathrm{m}, 10 \mathrm{x} 10\mathrm{m}$ , and $5 \mathrm{x} 5 \mathrm{m})$ of forest canopy were estimated and compared based on a voxel-based model using airborne LiDAR data and terrestrial LiDAR data, respectively. The LAD profiles retrieved from airborne LiDAR data were different from those obtained by terrestrial LiDAR data. The height of the maximum LAD estimated from the airborne LiDAR data was significantly higher than that estimated from the terrestrial LiDAR data. In addition, the middle and lower parts of the forest canopy LAD were underestimated by airborne LiDAR while the upper part of the forest canopy LAD were underestimated by terrestrial LiDAR compared with the actual canopy vertical structure.