By Jens van der Zee
Crown shyness describes the phenomenon in which tree crowns avoid growing into each other, producing an impressive puzzle-like pattern of complementary tree crowns in the canopy. Previous studies defined crown shyness in terms of canopy cover or intercrown distance and found that crown shyness is related to structural characteristics of the trees such as tree slenderness and size differences. This study aimed to expand the current set of models for crown shyness by quantifying the characteristic of surface complementarity among tree crowns displaying crown shyness using terrestrial LiDAR data. Subsequently, the relationship between crown surface complementarity and structural characteristics of the trees was analysed to verify whether previous models for crown shyness show agreement with the model developed in this study. A metric that quantifies the surface complementarity (Sc) of a pair of docking protein molecules is adopted from Lawrence and Colman (1993) and applied to the point clouds of pairs of adjacent trees. Three-dimensional tree crown surfaces were generated from the point clouds by computing their -shapes. Pairs that were visually determined to be overlapping scored significantly lower Sc values than pairs that did not overlap (n=14, p < 0:01). Furthermore, average slenderness of a pair of trees correlated positively with their Sc-score (R2 = 0:49, p < 0:01), showing accordance with previous studies on crown shyness. The results indicate that the 3D model for crown shyness developed in this study may contribute to future research on crown shyness. However, testing the model on a larger set of pairs is necessary to confirm its usefulness.
Keywords: crown shyness; complementarity; alphashapes; terrestrial LiDAR; forest canopy; tree slenderness