Growth and yield of Acacia mangium based on permanent sampling plots in a plantation

Acacia mangium is a very fast growing species belonging to the family fabaceae. It has been introduced in plantations in Sarawak, Malaysia for its rapid growth and wide range of adaptability. These plantations are anticipated to play the important roles in maintaining the commercial supply of logs thus reducing timber demand from the natural forests. Many plantations now used genetically improved material whose characters and properties have been improved through many years of research. Thus the study of growth and yield are crucial in order to have a more proper planning and management of this forest resource. This study assessed the growth and yield of the two acacias namely Acacia mangium superbulk or Acacia superbulk which is actually a second generation A. mangium and Acacia hybrid. The data obtained from permanent sampling plots (PSPs) of DAIKEN Plantation Sdn. Bhd. Bintulu were analysed to determine their mean annual increment (MAI) and periodic annual increment (PAI) in terms of diameter at breast height (DBH) and volume. Survival rate reduced as age of stand increased. Although DBH and height increased in size but the mean annual height and DBH increments decreased with age. The largest mean DBH recorded for Acacia superbulk and Acacia hybrid PSPs were 23.6 and 25.6 cm, respectively. Mean total height measured for Acacia superbulk and Acacia hybrid PSPs were 32.4 and 30.2 m, respectively. The highest volume mean annual increment was 27.4 m3 /ha/yr (6.9 years old) and 26.5 m3 /ha/yr (7.4 years old) for Acacia superbulk and Acacia hybrid, respectively. Initially growth in volume increased then began to decrease from seven years. Results of the four PSPs indicated that the maximum growth in volume per ha was attained at approximately seven years old stands