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Biomass and Carbon Sequestration Prediction Models for Acacia mangium Willd Plantations in Thai Nguyen Province, Vietnam
Dissertation Abstract:
The study developed a model to estimate current biomass and carbon stocks as well as predict future biomass and carbon sequestration potential for forest plantations of Acacia mangium Willd in Thai Nguyen Province, Vietnam. Specifically, the study: 1) characterized the Acacia mangium Willd plantation in Thai Nguyen Province, Vietnam; 2) estimated the current biomass and carbon stocks of tree and stand for Acacia mangium Willd plantations; 3) developed a biomass and carbon models for tree of Acacia mangium Willd; 4) determined the future conditions of plantation based on the programs and policies of the government; and 5) recommended appropriate management strategies to improve the forest plantation development and management.
A total of 126 plots representing various ages of plantations were established at the bottom, hillside, and hilltop of the plantation. Data collected from each plot included age of plantation, spacing, density, diameter, total height, basal area, and volume. Estimates of the various plantation characteristics showed significantly higher values in the bottom compared with those in the other parts of the plantations sampled.
The data for biomass and carbon estimation and development of prediction model came from 54 destructive sampled trees of different diameter classes (big, medium, and small) of the different ages. Six candidate non-linear regression equations using variables as diameter, total height, and age of plantation were tested and assessed for statistical validity and accuracy in biomass and carbon prediction. Data analysis was carried out in Excel and STATA 14 PM software. The study showed that the major biomass and carbon of tree are boles, followed by branches and leaves. Biomass and carbon models were tested for separated ages (each age class was tested by the model), as well as all age levels from ages 2 to 7 Acacia mangium Willd plantation (all age classes from 2 to 7 were tested by the model). In terms of separated ages, the model with one variable as diameter (D) showed the better values than variable height (H) and two variables (D, H) combined due to the high correlation efficiency (R2), small standard error (SE), and higher F values. As for the models tested for all age levels combined with the addition of the variable age (A), there was no significant difference observed between single predictor and combined predictors. The accuracy of the values was tested by chi-square and residual analysis to compare between observed and predicted biomass and carbon.
The prediction equations were used to assess future biomass and carbon sequestration in the province. Scenarios of biomass and carbon change were assessed based on the programs and policy of the government.