Relationship between aboveground biomass and measures of structure and species diversity in tropical forests of Vietnam

Tropical forests play an important role in storing carbon through aboveground biomass (AGB) and are considered the highest biodiversity ecosystem on earth. However, the quantitative relationship between AGB and structure-species diversity is poorly understood. Twenty-eight 1-ha plots from old-growth tropical evergreen broadleaf forests and dry dipterocarp deciduous forests, distributed in six ecological regions throughout Vietnam, were used for large tree census (diameter at breast height ⩾ 10 cm). Measures of biodiversity (species richness, Shannon index, and evenness) and of structure-species diversity (biomass-species and abundance-biomass-species diversities) were used to determine the patterns and strengths of relationship between each measure and AGB. The linear, logarithmic, and exponential patterns were found, however the former dominated. Negative linear and exponential patterns represented relationship between evenness and AGB, while positive linear and logarithmic relationships were most suitable for others. In general, site - specific relationships (R2 > 0.6) were much stronger than inter - site relationships (R2 < 0.6). Meanwhile, relationships between measures of biodiversity and AGB (the lowest R2 = 0.14) were generally weaker than that between measures of structure-species diversity and AGB (the lowest R2 = 0.31). This finding indicates that structure-species diversity is a sound index representing the role of tropical forest in storing biomass and may suggest that uneven-aged and multistoried plantations should be encouraged for carbon sequestration.