Taper, volume, and bark thickness models for spruce, pine, and birch in Norway

Taper models, which describe the shape of tree stems, are central to estimating stem volume. Literature provides both taper- and volume models for three main species in Norway, Norway spruce, Scots pine, birch. These however, were mainly developed using approaches established over 50 years ago, without consistency between taper We tested eleven equations six bark thickness. The fitted evaluated a large dataset covering all forested regions Norway. selected converted into functions numerical integration, providing with- without-bark volumes compared operational use. resulted root mean squared error (RMSE) 7.2, 7.9, 9.0 mm birch respectively. Bark thickness RMSE 2.5, 6.1, 4.1 mm, Validation with 12.7%, 13.0%, 19.7% Additional variables, age, site index, elevation, live crown proportion, resulting any strong increase predictive power.