| Teak(Tectona grandis L.f.),as a large deciduous or semi-deciduous tree species of Tectona of Verbenaceae,is a world-famous timber species.It has the advantages of rapid growth,durability and excellent wood quality.The development of teak plantation in China is seriously hindered by high planting density,improper fertilization,long rotation and slow return of economic benefits.Therefore,in this study,dominant or average teak trees in a7-years-old plantation with density and fertilization experiments in Fengting Township,Luodian County,Guizhou Province were selected to investigate the growth characteristics,tree form quality and branch development of teak clones.The basal diameter,chord length,branch angle and azimuth angle of the branches of the sample plants were measured,and the branch development characteristics of teak clones under different densities,configurations and fertilization treatments were analyzed in order to reveal the formation characteristics of knot free timber of teak and provide reasonable management decisions for forest managers.The main results were as follows:(1)By studying the growth and stem form of teak clones with different densities and configuration,the results showed that density,configuration mode and the interaction of both showed significant differences on tree height,DBH,volume per plant,volume per hectare and crown width.Density,configuration mode and the interaction between density and configuration mode had no significant effect on stem form and quality.Combining both growth and form quality index,density C was the best,the second was density B,density A was the worst.The growth and form quality of teak clones with different configurations were in order of configuration 2,3 and 1.Combined with the data of height,DBH,volume per plant,volume of trees,height under live branches and crown width,the density distribution of better and worse growth of teak clones were C2 and B1,respectively.(2)The results showed that the average basal diameter of total branch,living branch and dead branch increased with the decrease of planting density,but the trend was not significant.The average basal diameter of live branches was significantly different between uniform and non-uniform planting modes,but not for the total branches and dead ones.The density of C2 with larger average chord length of total branches,live branches and dead branches was C2,and the smallest was B1.The average chord length of total branches,live branches and dead branches increased significantly with the decrease of density.The average chord length of total branches and live branches from large to small was non-uniform configuration 2(narrow plant and narrow row type),non-uniform configuration 3(narrow plant and wide row type)and uniform configuration 1(uniform density type).For the average chord length of dead branches,there was no significant difference among the three configurations。Different densities had no significant effect in the number of total branches and live branches of teak,but the number of dead branches in B and C treatments was significantly different.The number of total branches,the number of live branches and the number of dead branches of teak were not significantly affected by the configuration mode.Among the nine density configurations,B2 had the largest total number of branches,while B1 had the smallest number.There was no significant effect on the number of live branches of teak with different densities.The density configuration with higher dead branch number was A2,C1,C3,and B1 was the least.The average branch angles of total branches,live and dead branches under 8m of teak clones decreased with the decrease of density,and the trend was obvious.The average branch angles of total branches,live and dead branches were 62.5～63.5°,60.3～61.4°and 54.2～55.3°,respectively.The average branch angles of the total branches,live and dead branches of teak clones below 8m were significantly different with the different configurations,which showed that the average branch angles of configuration 1 were greater than that of non-uniform configuration 2 and less than that of non-uniform configuration 3,and the differences were significant.The average branch angles of the dead branches in different configurations were configuration 1,configuration 2 and configuration 3,and there were significant differences among them.Under different densities,different configurations and different densities configuration,the change of branch angle of total branch and living branch was consistent.This was because the number of dead branches obtained from investigation was less,so the average branch angle of living branch could largely represent the average branch angle of total branch of teak clone.(3)The results showed that there were significant differences in tree height,DBH,volume per plant,volume,height under live branches,crown width and shape quality scores among different fertilization treatments.According to the principles of tree height,breast diameter,individual plant volume,accumulation volume,crown width as large as possible and height of live branches and stem score as high as possible,the fertilization treatment with better growth and shape performance was selected 2,3,4.5 and fertilization treatment 10 with poor growth and shape performance.(4)The results showed that different fertilization treatments had no significant effect on the average basal diameter of dead branches of teak clones.The average basal diameter of total branches in fertilization treatment 9 was the largest,reaching 25.19 mm,and that of live branches in fertilization treatment 6 was the largest,reaching 27.69 mm.Fertilization treatment10 had the smallest average basal diameter of total branches and live branches,with an average basal diameter of 19.78 mm and 21.61 mm.The minimum average chord length of total branches,live branches and dead branches was treatment 10,and the corresponding chord lengths were 1.33 m,1.41 m and 0.96 m,respectively.Fertilization treatments with larger average chord length of total branches were 1,5,6 and 9,while fertilization treatment with larger average chord length of live branches was 6 with chord length of 2.05 m.Different fertilization treatments had no significant effect on the number of dead branches.The total number of branches,live branches and dead branches were about 30,22 and 8 respectively.The average branch angles of total branches,live branches and dead branches of teak clones were 57.38° to 62.81°,55.16° to 59.80° and 62.38° to 70.78°,respectively.The average branch angle of dead branches of teak clones with different fertilization treatments was higher than that of live branches.In the horizontal direction,the basal diameter,chord length and branch angle reach the maximum or larger values in the azimuth range of 0 ～ 90°.Except for fertilization treatments 3,8 and 10,the basal diameter of branches in other treatments first decreased and then increased with the increase of azimuth angle;except for fertilization treatment 2 and 8,the chord length of branches of other treatments decreased first and then increased with the increase of azimuth angle,and reached the minimum value in the range of 181～270° in the southwest.The change of branch angle with fertilization treatment was more complex,except for treatment 4,the branch angle of other treatments was significant.This was mainly related to the light conditions,the better was the azimuth range(0～90° and 91～180°),the worse was the azimuth range(181～270° and 271～360°).In the vertical direction,the change of basal diameter and chord length of branches with different fertilization treatments were more complex with the increase of vertical height,and the change of basal diameter and chord length of branches with vertical height were consistent.There was no significant difference in basal diameter and chord length of branches in 2,3,5,9 and 10 treatments,but significant differences were found in other treatments.There was no significant difference in branch angle between 5 and 9treatments with the increase of vertical height of teak clones,but significant differences were found in other treatments.Except for fertilization treatment 8,the branch angle of other treatments reached the maximum value within 0-2 m or 2.01-4 m,and the branch angle was between 61.04 and 72.45°;except fertilization treatment 4,the branch angle of other treatments decreased from 4.01 to 6 m or 6.01 to 8 m,and the branch angle was between 55.26 and65.10°.In summary,C2 combination with low density and non-uniform configuration can be selected.The growth of teak clones was better,but basal diameter,chord length and number of branches were larger,which was easy to form knots.Therefore,teak plantation can be pruned in time by combining pruning technology.In the work of pruning,selecting dominant wood for pruning can control the cost of pruning,which was conducive to the formation of large diameter without knots.Or choose the medium density and uniform distribution mode B1,the growth of teak clones was not good,the basal diameter,chord length and the number of branches were relatively small,and then through reasonable fertilization,improve the growth of teak.This was not only conducive to the cultivation of big-diameter timber,but also conducive to the formation of non-knot timber. |
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