A model for the structural growth of young Scots pine crowns based on light interception by shoots

A model for the structural growth of the crown of a young Scots pine (Pinus sylvestris) is described. Each shoot produces new shoots, whose number and length are linearly related to the length of the parent shoot. The length of parent shoots is computed from the amount of direct and diffuse radiation intercepted by the parent shoot during the previous growing season. This procedure utilizes the spatial distribution of shoots (location, azimuth, inclination) produced by the growth process, and the structure of the shoots as determined in terms of the needle density, needle angle and length of needles with no need in advance to specify the statistical distribution of shoots in the crown space. The computations indicate that shoot structure could have only a negligible effect on the total light interception compared to the total needle area and its distribution within the crown. The modelling based on modular growth with a shoot as a basic computational unit seems to have great potential in describing the interaction between the tree crown and light conditions and the structural development of the crown system.