Effect of Planting Density on Production of Acacia Plantations in Northeast Vietnam

Acacia plantations have been contributing to national economic and livelihood of millions people living in rural areas of Vietnam. It has been widely planted and accounted for nearly 50% areas of plantations in Vietnam. In this study, different planting densities including 1,110 trees ha-1 (3 × 3 m), 1,330 trees ha-1 (2.5 × 3 m), and 1,660 trees ha-1 (2.5 × 2.5 m) were tested for Acacia hybrid and Acacia auriculiformis. The growth parameters (diameter at breath height/DBH and stem height/H) were measured, and dry biomass was estimated for 4-year-old plantations. The results indicated that a 4-year-old plantation of A. hybrid had most massive DBH (11.3 cm) at planting density of 1,100 tree ha-1, while highest dry biomass (57.9 Mg ha-1) was observed in planting density of 1,660 trees ha-1. In case of a 4-year-old plantation of A. auriculiformis, highest DBH (10.0 cm) and highest dry biomass (50.4 Mg ha-1) at planting density of 1,330 trees ha-1 were recorded. At the planting densities of 1,110 trees ha-1 and 1,660 trees ha-1, a 4-year-old plantation of A. hybrid had significantly higher dry biomass as compared to that of a 4-year-old plantation of A. auriculiformis. However, the difference of dry biomass between 4-year-old plantations of two species at planting density of 1,330 trees ha-1 was not significant. This study concluded that to grow A. hybrid planting density of 1,660 trees ha-1 should be used, while density of 1,330 trees ha-1 is encouraged for planting A. auriculiformis for pulpwood production.