Estimating merchantable timber volume of aspen and spruce stands of the boreal forest using airborne scanning laser altimetry

摘要

Pre-harvest estimations of merchantable timber volume are crucial for successful operational forestry but constitute a difficult task, as ground surveys are expensive, and remote sensing methods give inaccurate results. In the last fifteen years, a few experiments demonstrated the potential of laser altimetry for various forest measurements, including timber volume. Progress in inertial systems, GPS, and lidar technology now allows accurate high density coverages of the forest to be produced by laser altimetry. We flew Optech's ALTM1020 lidar over aspen and white spruce stands of the boreal forest of the Abitibi region, Quebec. Thirty-eight 400 m~2 plots located In these stands were measured to provide accurate ground estimates of their merchantable timber volume. The first and last lidar returns were independently interpolated to produce DTMs for the canopy and ground respectively. The difference between the DTMs yields a canopy height model on which different measures were performed. The ground estimates were first correlated to the lidar measurements. A timber volume prediction model was then constructed based on the best correlated parameters. The best model comprised a lidar based canopy volume estimate and a percent cover estimate. The R~2 for this model reached 0.81 in the case of aspen stands, despite being evaluated over a narrow range of volumes.