Impact of geometrical traits on light interception in conifers: Analysis using an FSPM for Scots pine

The main principle in functional-structural plant models (FSPMs) is the interaction between plant structure and eco-physiology. One aspect where the structure is of special importance is the complex calculation of light distribution in a plant which is in many models the basis for photosynthesis calculation. In this work we try to quantify the importance of geometrical traits for light absorption in conifers, using the LIGNUM model for Scots pine, and a method of global sensitivity analysis for selected geometrical parameters at needle (angle, length) and shoot (branching and bending angles, radius to length ratio) scale. While all the simulations were executed on GroIMP, sensitivity analysis was performed in PYGMALION. A new interface was created to enable the communication between GroIMP and PYGMALION software using a black-box approach, with the overall workflow controlled by PYGMALION. First results of sensitivity analysis showed that needle length had the highest impact on light interception during the whole studied period of 10 years, followed by needle angle during the first 7 years. The sensitivity to both parameters had a decreasing tendency. Impact of radius to length ratio was very similar to branching angle of the higher order branches; very low during the first years of the simulation, with increasing tendency. After the first 7 years, it was higher than the one of needle angle. There was no impact of branching angle for branches connected to the trunk and of bending angle during the studied time period.