Evaluation Of Canopy Structure Of Tall-spindle Apple Trees With Different Tree Ages Based On Three-dimensional Model

The rationality of the light distribution in the apple tree canopy is the basis for the high yield of the fruit tree,but the evaluation of the light distribution in the canopy has always been a difficult topic for fruit tree researchers.The three-dimensional digital technology can accurately describe the canopy structure.Therefore,in this study,in order to accurately evaluate the canopy structure of the high-spindle Fuji apple tree and clarify the growth rule of the high-spindle tree canopy,the M26 interstock short-branch Fuji was used as the test material,and the fruit trees of 4,8,and 12 years of age were selected as the three treatments.Manual measurement and statistics of the basic information of the canopy and branch group structure of each age,to construct the virtual tree model of the fruit trees of three tree ages,to compare the actual tree photos and the virtual tree,and to calculate total leaf area,projected leaf area,silhouette to total leaf area ratio STAR value,leaf area index and other indicators of the fruit tree based on the constructed three-dimensional model.To establish three virtual orchards of tree age,and calculate the light interception efficiency STAR value of a single fruit tree and the shading effect of the canopy,using a canopy analyzer LAI-2000measured the LAI of the canopy of each tree age,and compared and verified with the model calculation results,measured the fruit quality of the stratification,and studied the relationship between it and the STAR value of the light interception efficiency,and obtained the following main results:1.The basic indicators of the canopy of high-spindle apple tree stem height and crown amplitude increase significantly with the growth of tree age,and there is no significant difference between tree height and main branch amount;There was no significant difference in measurement statistics.2.Compared with the actual tree photo,the virtual tree image can show the actual growth of the tree as a whole;the average branch quantity,total branch length,and number of leaves of fruit tree canopy increase significantly with the growth of tree age,The total leaf area and projected leaf area of the canopy of fruit trees at 3 ages of the tree were 6.41m~2,11.60m~2,19.69m~2and 2.38m~2,3.88m~2,5.77m~2,respectively,which increased significantly with the growth of tree age.The silhouette to total leaf area ratio STAR values were 0.37,0.33 and 0.29,decreased with the growth of tree age,and there was no significant difference between them,LAI was 1.78,3.87 and 3.28,respectively;the STAR value of vegetative long branches,short branches of auxiliary shoots and fruit-bearing branches in the canopy of 4-year-old fruit trees was significant.greater than 8-and 12-year-old fruit trees,there was no significant difference between 8-and 12-year-old fruit trees.3.Under the condition that the STAR value of the light interception efficiency of a single fruit tree does not decrease significantly with the increase of the number of fruit trees in the orchard,the suitable number of fruit trees in the virtual orchard is 25.In the virtual orchard with the number of 25,the STAR values of 4-,8-,and 12-year-old fruit trees calculated by simulation were 0.30,0.18,and 0.19,respectively.There was no significant difference among fruit trees,and the canopy shading effects of the three tree ages were 0.19,0.45,and 0.34,respectively.4.The average light transmittance and canopy opening of fruit tree canopy decreased significantly with the increase of tree age,but there was no significant difference in leaf inclination angle.Using the canopy analyzer LAI-2000 to compare the measured leaf area index of all three-dimensional digitized tree canopies with the simulated value calculated by the three-dimensional model,the regression root mean square error(RMSE)value was0.171,indicating that the three-dimensional model of high accuracy.5.The single fruit weight,soluble solids,and chroma a*of the fruit increase with the height of the canopy in the heights of 0～150cm,0～250cm,and 100～250cm,respectively.The hardness and titratable acid are at 50,respectively.The height of～250cm and above100～250cm shows a continuous downward trend,and the fruit quality generally improves with the increase of canopy height;various indicators of fruit quality are related to the canopy STAR value,among which the single fruit weight and soluble solids The hardness decreased with increasing STAR value.To sum up,3D digital technology can establish a 3D model of the fruit tree canopy and use it for accurate evaluation of the canopy structure,and can analyze the lighting conditions of each part of the canopy and a single fruit tree in the virtual orchard.The silhouette to total leaf area ratio of the canopy is stronger in the saplings of the spindle-shaped short-branched Fuji fruit tree,and it will decrease with the increase of tree age.However,in the virtual orchard,the silhouette to total leaf area ratio of the fruit tree increases significantly with the increase of tree age.Pay attention to reducing the amount of light mutual shading in the canopy.