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van der Zee, Jens Understanding crown shyness from a 3D perspective Poster
Jens van der Zee1, Alvaro Lau1 and Alexander Shenkin2
(1) Wageningen University, Netherlands(2) University of Oxford, UK

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 was positively correlated with tree slenderness, supporting the theory that physical contact between trees through collisions plays a role in the formation of crown shyness. This study aimed to expand the current set of models for crown shyness by quantifying the characteristic of surface complementarity between tree crowns displaying crown shyness, using terrestrial LiDAR data. Subsequently, the relationship between crown surface complementarity and tree slenderness was analyzed to verify whether previous models for crown shyness show agreement with the model developed in this study.

A metric that quantifies the surface complementarity ($S_c$) of a pair of docking protein molecules was adopted from Lawrence and Colman (1993) and applied to the point clouds of pairs of adjacent trees. Tree crown surfaces were generated from the point clouds by computing their alpha-shapes. Pairs that were visually determined to be overlapping scored significantly lower $S_c$ values than pairs that did not overlap ($n=14$, $p < 0.01$). Furthermore, average slenderness of a pair of trees correlated positively with their $S_c$-score ($R^2 = 0.49$, $p <0.01$), 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 tree pairs is necessary to confirm its usefulness.

References:

Lawrence, M. C. and P. M. Colman

1993. Shape Complementarity at Protein/Protein interfaces.