Functions for Predicting Crown Height of Pinus sylvestris and Picea abies in Sweden

The aim of the study was to establish single-tree functions to predict crown height, defined as the height from the ground to the attachment of the lowest living branch to the trunk. Data from the Swedish National Forest Inventory 1983-1992 were used to construct country-wide functions for Scots pine (Pinus sylvestris L.) and for Norway spruce (Picea abies (L.) Karst.). The model derived was based on the assumption that crown recession in closed forests is caused primarily by lack of light. A crown height function and a relative crown height (crown height/total tree height) function were calculated for each species and were found to predict crown height fairly accurately. Crown height was generally predicted more accurately for Scots pine than for Norway spruce. The crown height functions developed here can be used as an input for predicting the quality of timber. The functions are meant to form part of a system for the long-term forecasting of timber yields, but they can also be used in calculations of the timber quality of a stand.