Aboveground tree biomass, carbon stocks and tree diversity in a mixed forest plantation in Northern Vietnam

Abstract

Tropical forests reserve a huge amount of carbon stocks and contribute to the amount of biomass accumulation above- and below-ground and the global carbon cycle. Forest plantations in the tropics have long been recognized as an effective solution in reducing the rate of increase in CO2 in the atmosphere. Moreover, the information on forest biomass and carbon content is necessary to support sustainable forest resource management in the world generally and in Vietnam particularly. Most of the forest plantations included only one tree species nevertheless, the use of two or more tree species during the planting phase and the plantation diversification are becoming more and more frequent. Within the framework of BioEcoN project, a Marteloscope, covered an area of 1 hectare, was set up in Hoa Lac Campus of Vietnam National University, Hanoi, Vietnam. Data collected from the Marteloscope include diameter at breast height (1,3 m above the ground), total height, species identity and position of 507 trees. Carbon stocks and above ground tree biomass by compartments were calculated using different biomass equations obtained from the relevant literature. The relationship between above ground tree biomass and species diversity were examined using regression analysis in which predictor variables are a set of parameters for the characterization of mixed stand structure include stand density and diversity, species intermingling, horizontal and vertical tree distribution pattern. The results show that the study area embraces 110.66 tons/ha of tree aboveground biomass and 55.33 tons/ha of carbon. Furthermore, results from the calculation of indices for characterizing species richness and diversity indicates high diversity and high evenness in the community. Although the study area is said to be a plantation, the results from a set of measures, indices, and methods for characterization of tree distribution patterns illustrate random distribution patterns. The sensitivity analysis of the optimum model fitted to explain the relationship between above ground tree biomass and species diversity indicates that above-ground biomass and carbon content decrease as the species diversity increase.