Assessing the Effects of Sample Size on Parametrizing a Taper Curve Equation and the Resultant Stem-Volume Estimates

: Saarinen, Ninni; Kankare, Ville; Pyörälä, Jiri; Yrttimaa, Tuomas; Liang, Xinlian; Wulder, Michael A.; Holopainen, Markus; Hyyppä, Juha; Vastaranta, Mikko

Publisher: MDPI

: BASEL

: 2019

: Forests

: FORESTS

: 848

: 10

: 19

: 1999-4907

DOI: https://doi.org/10.3390/f10100848

Large and comprehensive datasets, traditionally based on destructive stem analysis or other labor-intensive approaches, are commonly considered as a necessity in developing stem-volume equations. The aim here was to investigate how a decreasing number of sample trees affects parametrizing an existing taper curve equation and resultant stem-volume estimates. Furthermore, the potential of terrestrial laser scanning (TLS) in producing taper curves was examined. A TLS-based taper curve was derived for 246 Scots pines (Pinus sylvestris L.) from southern Finland to parametrize an existing taper curve equation. To assess sensitivity of the parametrization regarding sample size, the number of Scots pines included in the parametrization varied between full census and 1 Scots pine at a time. Root mean square error of stem-volume estimates remained <= 20.9% and the mean absolute difference was relatively constant (<= 9.0%) between stem-volume estimates when the sample size included >= 46 Scots pines. Thus, it can be concluded that, with a rather small sample size, a taper curve equation can be re-parametrized for local conditions using point clouds from TLS to produce consistent stem-volume estimates.