Relascope sampling for crown ratio estimation

• Main Authors: Schnell, Sebastian, Wikman, Jonas, Ståhl, Göran
• Format: Article in Journal/Newspaper
• Language: Swedish; English
• Published: 2013
• Subjects: Forest Science; Northern Sweden
• Online Access: https://pub.epsilon.slu.se/11091/; https://pub.epsilon.slu.se/11091/1/Schnell_et_al_140513.pdf

In this study, we apply vertical angle count sampling to estimate the crown ratio of trees in unthinned forest stands. The rationale is to be able to quickly assess the relative crown size of forest stands to support thinning decisions by simply counting trees. We provide estimators and discuss their precision based on pilot studies in Scots pine (Pinus sylvestris L.) plantations in northern Sweden. A separate study was conducted to investigate the amount of measurement errors, i.e., how many trees are wrongly selected or overlooked when using the method. Sampling errors for estimating crown ratio were found to be remarkably low, partly due to high correlation between crown length and tree height and partly due to low variability in the study sites. Measurement errors were in the range of what is commonly obtained with horizontal angle count sampling for basal area estimation.