Fractal characteristics of two-dimensional images of 'Fuji' apple trees trained to two tree configurations after their winter pruning

The structural diagrams of apple trees are the comprehensive reflection of the effects of their training and pruning as well as their physiological and ecological characteristics and yield. However, there have been few research reports on the characteristics of the structural diagrams of apple trees. The study investigated the fractal dimension numbers and fractal characteristics of the two-dimensional images of 5-year-old and 10-year-old 'Fuji' apple trees trained to the tall spindle configuration and the open-center configuration employing box-counting in combination with the image processing technology of the Photoshop. The two-dimensional images of apple trees with the different configurations differed and varied with their ages. The fractal dimension numbers of the two-dimensional images of the 10-year-old apple trees with the tall spindle configuration and with the open-center configuration were 1.6625 and 1.6531 respectively while the fractal dimension numbers of the two-dimensional images of the 5-year-old apple trees with the tall spindle configuration and with the open-center configuration were 1.6429 and 1.6377 respectively. As the age of the apple trees increased, the spatial quantities and distributions of trunks and branches got slightly intensified, and the fractal dimension numbers of their two-dimensional images and the apple yield increased correspondingly. The comparison of the fractal characteristics of the apple trees with the same age, which were trained to the different configurations, revealed that under the same age, the branch quantities and the apple yield of the apple trees with the tall spindle configuration were higher than those with the open-center configuration, so that under the same age the fractal dimension numbers with the tall spindle configuration were higher than those with the open-center configuration. These results showed that the fractal dimension number of the two-dimensional images of apple trees depended upon their trunk and bough distribution and at the same time it increased with their apple yield as well. Therefore, the fractal dimension numbers of the two-dimensional images of apple trees could be employed as an indicator for assessing training and pruning effects on apple trees and their fruit yield. (C) 2011 Elsevier B.V. All rights reserved.