Research On The Fractal Dimension And Three-Dimensional Digitized Modeling And STAR Value Of ’Fuji’ Apple Trees Trained To Tall Spindle Shape

The structure of a tree directly affects its canopy light interception, leaf function and fruitquality. The main purposes of pruning and training is to establish a reasonable and highphotosynthetic efficiency tree structure, but in the actual production lack of simple, accurateassessment methods for the tree structure and light interception in the canopy. This paperintroduced fractal theory and digitized method to study the ‘Fuji’ apple trees trained to tallspindle shapes (Malus domestica Borkh cv. Fuji). We used2-year-old trees of tall spindle shapeas materials, and the characteristics of growth potential of six cultivars were assessed usingfractal dimension.13-year-old tall spindle trees were digitized, and the three dimensionalstructure models of the large, middle and small canopies were reconstructed. The lightinterception of different types shoots and fruit in different position were assessed, and the fruitquality of fruits in different position were analysed. The purpose of this research was to findfeasibility indicators to assess canopy structure and light interception and provide theoryreference for the research on the training and pruning and canopy structures of fruit trees. Themain conclusions obtained were as follows:1、The fractal dimension of trees at the larger plant spacing could be used as an indicatorto assess the tree structureThe sorted order of shoot length and general fractal dimension of six cultivars of ‘Fuji’apple trees trained to tall spindle at1.5m plant spacing were ‘Li Gala’>‘YuhuaZaofu’>‘Honggailu’>‘Yanfu6’>‘Fuhong Zaoga’>‘Nagafu2’. The sorted order of fractaldimension of front-view, side-view and general2-D images were identical at1.5m plantspacing, while there was great difference at1.2m plant spacing. Shoot length was one offactors that influenced fractal dimension, which also depended on plant spacing. The fractaldimension of trees at1.5m plant spacing was greater than that of at1.2m. At1.2m plantspacing, the fractal dimension of trees belongs to ‘Gala’ series was greater than that of ‘Fuji’. It was not identical that the difference between fractal dimension of front-view and side-viewimages of trees for different cultivars at two plant spacing. It showed that the branchingpattern was different for different cultivars at different plant spacing, and the six cultivars at1.5m plant spacing showed consistent growth and branching mode.2、Fractal dimension can be used to guide the training and pruning of young treesExcept ‘Yuhua Zaofu’ and ‘Honggailu’, the fractal dimension of front-view images of theother four cultivars was greater than their side-view images. If there was enough space for‘Yuhua Zaofu’, they would born more branches and have better growth vigor. On the basis ofthe branching pattern of fruit trees, how many branches should be left can be determined by thevalue of fractal dimension, and the training and pruning extent of the adjacent fruit trees can bedetermined by the growth potential of cultivars under different plant spacing. Fractal dimensioncan characterize the effect of training and pruning. In other words, the advantage anddisadvantage of the tree structure and branching feature can be assessed by fractal dimensionand then further guide the training and pruning. The standard of evaluating tree structure isthrough the comparison between the most excellent tree structures, the degree of the studiedstructure can be identified through the proximity between the excellent fractal dimension andthe fractal dimension after training and pruning.3、The model of actual apple trees can be reconstructed based on the3D digitizerThe digitized shoots number was equal to the actual shoots number. Significant t testshowed there was no significant difference between artificial statistics and digital results in theshoots number. There was no significant difference between light transmittance measured bylight quantum sensors and computed based on the model. The measured value was the averagevalue of the light transmittance of the east, west, north and south directions under trunk base.Stratified the tree model and the measured results of fruit quality indicators of each layershowed that the single-fruit mass, firmness and soluble solid content on the top canopy werehigher than in the lower canopy, while the titratable acidity at the bottom were higher than atthe top; the luminance of fruit was highest at the lay of50cm to100cm in vertical direction;the three-dimensional distribution chart of fruits can be drawn according to the positioncoordinates.4、STAR value can be used as an indictor to assess light interceptionThe STAR of large, middle and small canopy increased successively. The ranking orderof the STAR value of different shoot types within large, middle and small canopy wasVL>BL>VS>BS>BF (BA). The STAR of fruits, bourse and short vegetative shoots showedvery significant differences and the STAR of fruits, long vegetative shoots and short bourse shoots showed significant differences. The STAR value increased along with the crownheight and had an extremely significant difference with soluble solid content and a*and positively related.The STAR value had an significant difference with the titratable acidity and L*and negatively related, andthe difference was significant and very significant respectively. Herein, the laws reflected by STAR wereconsistent with that of by PAR.