Developing production models and analyzing timber production variation of Acacia hybrid plantations on different sites in Dong Nai province

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The objective of this study was to analyze the variation in timber production in Acacia hybrid plantations based on age and different sites. Data were collected from 50 standard plots (25 × 20 m) of different plantation ages ranging from 2 to 10 years. The site condition of Acacia hybrid plantations were assessed using 5 site indices from I to V. Site index functions were developed from the height of 50 dominant trees at the age of 10. Production functions at the average tree level were constructed using data from 50 trees at age 10. The research results showed that 5 site indices of Acacia hybrid plantations had values of 28, 25, 22, 19 & 16 m, respectively. Timber production of Acacia hybrid plantations has changed markedly with age and site indices. The age of 2 could be the time when diameter and height of Acacia hybrid plantations change from the fast growing stage to the slow growing stage. By the age of 5, the timber volume of Acacia hybrid plantations changes from the fast growing stage to the slow growing stage. The average timber productivity of 10 year old Acacia hybrid plantations on 5 site indices from I đến V was 38.8, 28.6, 20.2, 13.6, & 8.5 m3/ha per year, respectively. The age of quantitative maturity of Acacia hybrid plantations on 5 site indices was 9 years of age.