Shading Characteristics Of Different Fruit Tree Shapes And Configuration Modes In Fruit-Agricultural Intercropping System In Western Shanxi Loess Region

At present,the research on interspecific relationship in fruit-farming system is mainly about the competition between water and fertilizer,but there are few studies on interspecific competition between light in this system,especially on the spatial and temporal changes and spatial distribution of canopy shading.In this study,two apple tree types(free fusiform and evacuation stratification)and different row spacing patterns(4m×5m and 5m×5m)were widely used in the loess region of Western Shanxi Province.Based on the law of solar apparent motion and the theory of parallel projection,theoretical shading models of different tree shapes were established,and different stages of soybean growing season and different times of the day(8:00-17:00)were taken as the research objects.The theoretical model of shading was validated and revised by the shading range measured on the spot.The temporal and spatial dynamic distribution of tree shading range in fruit farming intercropping system with different tree shape and row spacing was analyzed.The purpose of this study is to guide the selection of tree shape in the fruit-farming intercropping system in the study area,and to provide theoretical support for the definition of the intercropping area in the intercropping system,so as to promote the efficient utilization of resources in the local fruit-farming intercropping system and enhance economic benefits.The results show that:(1)Construction and accuracy evaluation of theoretical model of fruit tree shading:According to the measured basic eigenvalues of fruit trees,two different theoretical models of tree crown shading were established in this study.The boundary and area of shading image were verified on the spot,and the fitting accuracy of the model was higher:the actual value and rationality of the boundary of shading area of fruit tree under two kinds of tree-shaped fruit trees(free fusiform trees and evacuation stratified trees)The correlation coefficients of theoretical values were greater than 0.896(p>0.01);the regression coefficients of measured and theoretical values of shaded area were 0.993(R2=0.983)and 0.995(R2=0.990);the coincidence rate of theoretical shading and measured shading of two fruit tree crowns was over 93.76%.(2)Spatial and temporal distribution of shading for individual trees with different tree shapes:shading area,shading overlap area and cumulative shading time of free fusiform trees are less than those of evacuation stratified trees;With the development of crop phenology,the range of crown shading and overlapping shading increased gradually,and the length of shading became shorter;with the passage of time in a day,the range of crown shading and overlapping shading decreased first and then increased;the shading range in the north side of fruit trees was larger than that in the South side.Therefore,it is unreasonable to cultivate fruit trees with equal spacing on both sides of the north and South in the east-west direction of the study area,and the spacing between the north side of the tree row and the crops should be larger than that of the South side.(3)Spatial-temporal distribution characteristics and differences of shading of fruit trees under different plant-row spacing patterns:the overlapping shading area of adjacent trees with 4mx5m row spacing was larger than that with 5m×5m row spacing;under the same plant-row spacing,light competition of free fusiform trees was weaker,so the research area should give priority to the shape of free fusiform trees;during the phenological period of intercropping crops,with the date the shading zone between rows of fruit trees gradually shifted northward,and the shading overlap area of adjacent fruit trees became larger and larger.According to the length of shading time,the shading areas of 4mx5m and 5m×5m tree-shaped fruit trees were divided into non-shading areas(A),light shading areas(B1,B2)and heavy shading areas(C).Accordingly,the suitable planting areas in fruit-farming system under different plant-row spacing were proposed:For free spindle trees with row spacing of 4m X 5m,it is suitable to intercrop in the range of 1.16～4.33 m in the north and 0.67～2.86 m in the south,1.75～3.88 m in the north and 1.69～3.28m in the south,and 1.16～4.28 m in the north and 0.72～2.72m in the south of free spindle fruit trees with row spacing of 5m×5m.Intercropping was suitable in the range of 1.25～3.28m in the south.