| The apple yield and quality are closely related to light interception and utilization efficiency of group and individual canopies.Dwarf culture is the development direction of apple cultivation mode in the world,also is the development trend in China.The research about relationships between plant densities,tree forms and light interception and utilization in orchards with dwarf stocks has great theoretical significance and application value for guiding reasonable pruning and training,making full use of light energy,improving yield and quality and so on.According to the solar apparent motions and the spherical trigonometry,the differences in light interception and utilization efficiency of canopy in different attitude with different row spacing and tree forms were studied;theoretical and application models of light interception and utilization efficiency for tree canopies were established for modern apple orchards with dwarfing stocks.The spatial and temporal distribution of possible sunshine duration on the outer lowest point of canopy surface and relative radiant flux density in the center of canopy bottom in the whole growing season(from Apr.1st to Nov.30th)in 3 attitudes(30 °N,35°N and 40°N)with 4 kinds of row spacing(3.0 m,3.5 m,4.0 m and 4.5 m)and 3 kinds of tree forms(cone,truncated cone and cylindrical shapes)were calculated and systematically analyzed with C language programming.Based on the characteristics of light interception on the tree canopy surfaces and light propagation rule inside the tree canopies,the quantities of total branches and all kinds of shoots in orchards with high quality and high yield at different latitudes,different row spacings and different tree forms were profoundly expounded.According to temporal-spatial distribution data about solar radiation flux density and fruit tree biology measured and investigated in different training types of apple orchards,the established models were verified.The results are listed as follows:(1)According to the actual tree form,cross sections of tree rows were simulated into trapezoid,and distribution modes of leaves inside the canopy were assumed to be continuous uniform,the formulas to calculate the hour angles of sunrise and sunset at any point on the canopy surface in N-S row on flat areas were derived and possible sunshine duration(N)at the point in any day could be calculated.(2)Programming with C language,seasonal variation rules of possible sunshine duration at the outer lowest point of canopy surface during the whole growing season were found.Under the condition of the same latitude and canopy width,the possible sunshine duration decreases with the increase of height / row spacing.Under the condition of the same latitude and height / row spacing,the possible sunshine duration increases with the growth of canopy width,but it is not remarkable.Under the condition of the same latitude and canopy width,the possible sunshine duration of the canopy surface in the same height / row spacing presents the change rules of increasing during spring,getting maximums at the summer solstice day and then decreasing.In the whole growing season,light condition during spring is much better than that during autumn.(3)These optimized combinations of tree form,tree height,canopy width and row spacing which make group canopy obtain the largest light interception during the whole growing season in orchards on flat areas with 3 latitudes(30°N,35°N and 40°N),4 kinds of tree row spacing(3.0 m,3.5 m,4.0 m and 4.5 m)in N-S row and 3 kinds of tree form(cone,truncated cone shape and cylindrical shape)were calculated.If row spacing ranges from 3.0 m to 4.0 m,the suitable tree height / row spacing for the cone and truncated cone range from 0.70 to 0.85,while the ratio for the cylinder is 0.60 to 0.75.The less the row spacing is,the closer to the cylinder the optimized tree form is.(4)The distance formulas of sunshine radiant from incident point on canopy surface to the bottom center at any time in any day during a year was derived.The numerical relationship between relative radiant flux density on any point inside the canopies and row spacing,canopy width at different latitudes and row spacings was determined.Relationship between leaf area index and the relative radiant flux density of direct radiation and scattered radiation inside canopies during the whole growing season was explicated.Under the condition of the same tree form and extinction coefficient,the relative radiant flux density of direct radiation,scattered radiation and global radiation in the orchard rise with the increase of row spacing,and the relative radiant flux density of scattered radiation is bigger than that of direct radiation.All of the relative radiant flux density decrease with the increase of leaf area index.The larger the row spacing is,the more remarkable the decrease of the relative radiant flux density of direct radiation is.The seasonal variation of the relative radiant flux density of direct and scattered radiation is different.After the summer solstice day,the relative radiant flux density of direct radiation begins to decrease.The scattered radiation is less relative with seasons and reduces with the growth of leaf area index.(5)The relative light flux density at the group canopy bottom center was determined in NS row and 4 kinds of row spacing(3.0 m,3.5 m,4.0 m and 4.5 m)at flat areas around 3 latitudes(30°N,35°N and 40°N)during the spring-shoots-stop-growth period and the autumn-shootsstop-growth period respectively.Putting relative radiant flux density not lower than 30% in canopy bottom center,optimized leaf area index was calculated and optimized quantity of branches was obtained.In apple orchards around 30°N,the range of optimized branches quantities is from 7.22 × 105 to 9.64 × 105·hm-2 for 3.0 m row spacing,from 7.48 × 105 to 9.98 × 105·hm-2 for 3.5 m row spacing,from 7.79 × 105 to 1.04 × 106·hm-2 for 4.0 m row spacing and from 8.05 × 105 to 1.07 × 106·hm-2 for 4.5 m row spacing.In apple orchards around 35°N,the range of optimized branches quantities is from 6.97 ×105 to 9.27 × 105·hm-2 for 3.0 m row spacing,from 7.28 × 105 to 9.73 × 105·hm-2 for 3.5 m row spacing,from 7.62 × 105 to 1.02 × 106·hm-2 for 4.0 m row spacing and from 7.85 × 105 to 1.05 × 106·hm-2 for 4.5 m row spacing.In apple orchards around 40°N,the range of optimized branches quantities is from 6.77 × 105 to 9.04 × 105·hm-2 for 3.0 m row spacing,from 7.08 × 105 to 9.44 × 105·hm-2 for 3.5 m row spacing,from 7.37 × 105 to 9.84 × 105·hm-2 for 4.0 m row spacing and from 7.57 × 105 to 1.01 × 106·hm-2 for 4.5 m row spacing.(6)The canopy light inception and efficiency in the spring-shoots-stop-growth period is lower than that in the autumn-shoots-stop-growth period.To gain optimized interception and utilization efficiency of light,the decrement of total branches and all kinds of shoots in the autumn-shoots-stop-growth period is from 5% to 10% around 30°N;9% to 11% around 35°N and 11% to 15% around 40°N.(7)From 2015 to 2017,investigations on tree growth,sunshine distribution inside canopy,fruit yield and quality were carried out for trees planted at 2011 in different planting spacing(0.75 m,1.00 m,1.25 m and 1.50 m)and row spacing(3.0 m and 4.0 m)in Beijing(40.14°N,116.85°E),and the models were verified.The investigation showed that among the existing cultivation patterns in Beijing,the tree structure parameter and total shoot of the planting density of 4.0 m row spacing and 1.00 m – 1.25 m planting spacing are the closest to the optimal parameter of 4.0 m row spacing calculated by the model.The other tree parameters are far from the optimal parameter.The spur shoot proportion,relative radiant flux density inside canopy,fruit mass,soluble solid content and yield with 4.0 m row spacing and 1.0 m – 1.25 m planting spacing are higher than other planting patterns.These showed that the models of light interception and light utilization in apple orchards with dwarf stocks are relatively reliable. |
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