Estimation of leaf area index and covered ground from airborne laser scanner (Lidar) in two contrasting forests

Two canopy properties, leaf area index (LAI) and covered ground (CoverGnd), were estimated using hemispherical photography of three oak (Quercus pyrenaica) and eight pine (Pinus sylvestris) forest plots in Sierra de Guadarrama (central Spain). Pulses from airborne laser scanner (Lidar) that hit the surface on the exact location (within centimeter resolution) of the photographs were analyzed and separated by different radius size (from 0.5 to 20 m). The correlation between Lidar and hemispherical photography estimates of canopy properties was highly significant, but was affected by the type of forest and the radius size. CoverGnd was better estimated using a small radius size (2.5 m, equivalent to one fourth of canopy height), while LAI was better estimated using a larger radius size (7.5–12.5 m, equivalent to the entire canopy height). In general, the smaller the tree, the shorter the radius was that must be used to select Lidar data, and the best Lidar estimator of canopy properties was the percentage of canopy hits. Overall oak canopies showed better results than pine forest. The poorer estimation in pine forest plots was probably due to the larger foliage and branch clumping of pine versus oak canopies. Lidar data could be used to produce high-resolution regional maps of the canopy properties studied.