Bài 7
Keywords:
Sawlog,, Acacia hybrids,, silviculture techniques, Quang TriAbstract
This paper introduces the results of studying the effects of silviculture techniques to improve the productivity and quality of Acacia hybrids plantation for sawlog in Quang Tri province. After 4.5 years of age, the experimental
models had a survival rate of 86.67 - 92.5%, MAI (Mean Annual Increment) was reached 28.68 m3/ha/year. The formulas cutting and hashing vegetation on site and comprehensive clearance and clearing vegetation were have the best growth in the group with Diameter at Breast Height (DHB) was from 12.68 -12.81 cm, Height (H) from 14.24 - 14.39 m, Canopy Diameter (CD) from 3.55 -3.64 m. On the site condition of after logging, it was recommended to use the method of comprehensive clearance and clearing vegetation or comprehensive
clearance and even organic materials spread on the ground. Digging holes by machine 50 50 50 cm has the best growth with DBH 12.93 cm, H 14.72 m and CD 3.66 m. The growth ability of Acacia hybrids at different planting
densities was significantly different, DBH was gradually decreasing in the direction of increasing density and the largest DBH is 13.40 cm with density of 1,110 trees/ha. H was gradually decreasing in the decreasing direction of density and the highest average Height reached 14.14 m with the density of 1,660 trees/ha. The highest average CD reached 4.04 m with the density of 1,110 trees/ha and the smallest CD is 3.56 m with density of 1,660 trees/ha. The
initial planting density of 1,110 - 1,330 trees/ha are suitable for growing sawlog forests. Fertilizing 200g NPK (5: 10: 3)/tree give the best growth with DBH reached 12.69 cm, H reached 14.35 m and CD reached 3.76 m. The thinning intensity has a marked effect on the growth and stock of the experiment. At 6.5-years old, the formula of 1,300 trees/ha and 1,100 trees/ha had the best average standing volume of 170.04 m3/ha and 166.74 m3 /ha, MAI reached 26.16 and 25.65 m3/ha/year. The percentages of number of trees (DBH > 18 cm) was accounts for only 6% of the formula T900 (Nht 820 trees/ha). The highest percentages of number of trees - 18 cm) in T900 was 86.0% and the lowest in T1500 was 12.0%.
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