Ground-based laser imaging for assessing three-dimensional forest canopy structure

Improved understanding of the role of forests in carbon, nutrient and water cycling can be facilitated with improved assessments of canopy structure, better linking leaf-level Processes to canopy structure and forest growth. We examined the use of high-resolution, ground-based laser imaging for the spatially explicit assessment of forest canopies. Multiple range images were obtained and aligned during both leaf-off and leaf-on conditions on a 20 m X 40 m plot. The plot location was within a mixed species broadleaved deciduous forest in western North Carolina. Digital terrain and canopy height models were created for a 0.25 m square grid. Horizontal, vertical, and three-dimensional distributions of plant area index, created using gap-fraction based estimation, had 0.5 m resolution for a cubic lattice. Individual tree measurements, including tree positions and diameter at breast height, were made from the scanner data with positions, on average, within 0.43 m and diameters within 5 cm of independent measurements, respectively. Our methods and results confirm that applications of ground-based laser scanning provide high-resolution, spatially-explicit measures of plot-level forest canopy structure.