可搬型Scanning Lidarによるスギ林のバイオマス推定における誤差評価

概要

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In this study, forty 60-year-old Japanese Cedars (Cryptomeria japonica) at a study area of about 400 m2 were measured to estimate the tree position, the diameter at breast height (DBH) and the biomass using a portable scanning lidar with a high spatial resolution. As a result, 31 (78%) out of 40 trees were measured from one point, and the rest of tree positions were measured from 3 points including the first point mentioned. The DBH for each tree was estimated with a RMSE (Root Mean Square Error) of 6.1 mm when compared with ground-truth tape measurements. Then, the stem-biomass (carbon weight) was calculated by an existing quadratic equation (R2 = 0.843) using estimated DBH. The RMSE between the estimated stem-biomass and the stem-biomass evaluated based on a timber volume formula using the DBH was found to be 11.5 kgC/tree. Then the whole biomass (carbon weight including stems, branches, foliage and roots) of each tree was estimated by using existing quadratic equations (R2 = 0.843 for stem and R2 = 0.792 for branch, leaf and root) based on the relationship between the DBH and the biomass. Furthermore, estimation reliability according to the number of measured trees was examined by choosing trees by changing the degrees of the lidar. Results showed that the biomass per square meter was estimated with an error of about 12%, 5% and 3% in the case of 10 (25%), 20 (50%) and 30 (75%) measured trees respectively.