Measurement errors in forest inventories and comparison of biomass estimation methods

Abstract

Accurate quantification of above-ground biomass (AGB) in managed forests requires: consideration of inventory errors and the use of local or large-scale allometric models. In this study we focus on the measurement errors, data collection errors and we compared different methods to estimate AGB in managed tropical forest. The data were collected in 15 plots of 100 x 100 m. We evaluated the errors of the forest inventory of 8.898 trees. We used four methods to estimate AGB: three methods which use a pan-tropical equation, which depends on wood density data, with different ways of integrating the wood density data (obtained from dataset of the Brazilian Forest Service, Jari and Global Wood Density Database-GWDD); and one local equation. The main inventory errors were: problems with the same tree being identified as a different tree in consecutive measurements (16% of the trees). AGB estimates using each of the four methods were significantly different.

Influence of Scanner Position and Plot Size on the Accuracy of Tree Detection and Diameter Estimation Using Terrestrial Laser Scanning on Forest Inventory Plots

“…It was also interesting that the influence of the plot size varies depending on the scan variant. Those scan variants without a center scan (2,4,6,8) have a much lower detection rate up to a plot radius of 10 m than the comparable full variants. As was found in Kankare et al [81], the main problem of TLS data is that the point density decreases with the distance to the scanner.…”

“…The outer square had a side length of 14.1 m and the distance of each reference target to the center was 10 m. The inner square had a side length of 7.1 m and the distance of each reference target to the center was 5 m. In addition, the two squares were rotated by 45 • . In scan variants without a central scan (2,4,6,8), an extra reference target was placed at the center location.…”

“…The application of these traditional measurement techniques is time-consuming, cost-intensive, and prone to manifold measurement errors [5][6][7]. Recorded tree positions are often imprecise, as position, distance, and angle errors propagate, especially on rough terrain [8,9]. Trials to improve efficiency since the beginning of forest inventory have permanently enhanced techniques, instruments, and protocols [6].…”