Evaluating forest biometrics obtained from ground lidar in complex riparian forests

Terrestrial laser scanning is a technique that has been used increasingly in extracting forest biometrics such as trunk diameter and tree heights. Its potential, however, has not been fully explored in complex forested ecosystems, especially in riparian forests, considered among the most dynamic and complex portions of the Earth's biosphere. In this study, forest inventory data and multiple ground scans were obtained in a sparse managed and dense natural riparian forest on the immediate banks of the mid-lower portion of the Garonne River in Southern France, dominated by black poplar (Populus nigra) and commercial hybrid poplars (Populus × euramericana). Overall, the ground-based laser-scanning analysis successfully estimated trunk diameters, tree heights and crown radii from both managed and natural riparian forests. However, the ground scanner analysis was not as successful in identifying all of the trunks in the dense natural riparian forest, with only 141 trunks identified from a total of 234. This also results in allometric scaling exponents for ground scanning, which are significantly different from field-derived exponents. This study thus shows that there may be a limit to the number of trees detected in higher density forests, even with multiple scans.