The hardware and bandwidth for this mirror is donated by METANET, the Webhosting and Full Service-Cloud Provider.
If you wish to report a bug, or if you are interested in having us mirror your free-software or open-source project, please feel free to contact us at mirror[@]metanet.ch.
Taper models for spruce, pine and birch in Norway and helper functions
The taper models are based on Endre Hansen, Johannes Rahlf, Rasmus Astrup & Terje Gobakken (2023) Taper, volume, and bark thickness models for spruce, pine, and birch in Norway, Scandinavian Journal of Forest Research, DOI: 10.1080/02827581.2023.2243821 (https://www.tandfonline.com/doi/full/10.1080/02827581.2023.2243821?scroll=top&needAccess=true&role=tab) and correction, DOI: 10.1080/02827581.2024.2358467 (https://www.tandfonline.com/doi/full/10.1080/02827581.2024.2358467).
Taper models, which describe the shape of tree stems, are central to estimating stem volume. Literature provides both taper- and volume models for the three main species in Norway, Norway spruce, Scots pine, and birch. These models, however, were mainly developed using approaches established over 50 years ago, and without consistency between taper and volume. We tested eleven equations for taper and six equations for bark thickness. The models were fitted and evaluated using a large dataset covering all forested regions in Norway. The selected models were converted into volume functions using numerical integration, providing both with- and without-bark volumes and compared to the volume functions in operational use. Taper models resulted in root mean squared error (RMSE) of 7.2, 7.9, and 9.0 mm for spruce, pine, and birch respectively. Bark thickness models resulted in RMSE of 2.5, 6.1, and 4.1 mm, for spruce, pine, and birch respectively. Validation of volume models with bark resulted in RMSE of 12.7%, 13.0%, and 19.7% for spruce, pine, and birch respectively. Additional variables, tree age, site index, elevation, and live crown proportion, were tested without resulting in any strong increase in predictive power.
devtools::install_git("https://github.com/SmartForest-no/taperNOR")These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.