Stand Structure and Growth Drivers of Aboveground Biomass and Carbon in Acacia Plantations

Background and Objective: Understanding growth dynamics and carbon storage in plantation forests is essential for assessing their role in climate change mitigation. The main objective of this study is to quantify the aboveground biomass and carbon stocks in Acacia plantations and to identify the key stand structure and growth factors that influence biomass accumulation and carbon sequestration. Materials and Methods: This study examined tree growth, stand structure, and biomass allocation in Acacia plantations (11-15 years old) in Cambodia using descriptive statistics, ANOVA, correlation, and Principal Component Analysis (PCA). Results: The stands were relatively even-aged, with DBH averaging 19.3 cm and height averaging 18.8 m, but exhibited substantial variability in basal area, volume, and biomass. ANOVA revealed significant differences among age groups for height, bole height, and stand volume (p<0.01), while DBH, aboveground biomass (AGB), and carbon stock showed no significant variation. Correlation analysis highlighted DBH as the strongest predictor of biomass and carbon (r = 0.98), followed by tree height (r = 0.76). PCA further indicated that the first two components explained nearly 90% of the variance, with PC1 representing tree size and biomass (DBH, height, AGB, carbon) and PC2 representing stand structure (basal area, volume). Nonlinear modeling confirmed that the logarithmic height-diameter relationship provided the best fit (R² = 0.75, lowest AIC and RMSE). Conclusion: Overall, the findings demonstrate that carbon storage in Acacia plantations is strongly controlled by DBH and a few dominant trees, while stand density influences structural development. These insights highlight the importance of managing tree size and stand density to optimize biomass production and carbon sequestration in Acacia plantations of Cambodia.