Conclusions
Structural diversity at different scales can be linked to biodiversity and carbon uptake as well as attractiveness of landscapes and recreational activities. Possibilities for forest management in considering these more varied objectives are acknowledged but objective measures of structural diversity have been lacking as 3D information on structure of forests and trees has practically been unavailable before various laser scanning sensors. This study provides an example how structural complexity of individual trees can be quantitatively assessed and how it is affected by forest management. We demonstrated the use of so-called box dimension in characterizing structural complexity of individual Scots pine trees in managed plots. Thinning intensity affected structural complexity and intensive thinning resulted in increased structural complexity. Increasing crown size (i.e. width, surface area and volume) and tree growth also increased structural complexity but there was no relationship between structural complexity and benefit-to-cost ratio (i.e. relationship between crown surface area and stem volume) or light availability (i.e. competition). More research is required to better understand the specific drivers behind structural complexity of different tree species. For example, how regeneration and growth of other than traditional attributes (e.g. DBH and height) affect the structural complexity. It can be concluded that thinning had an effect on structural complexity of individual Scots pine trees and stem, crown, and growth attributes were identified as drivers for the structural complexity in managed boreal forests.