Calculation of Forest Carbon Stock

 Forest carbon stock refers to the process by which forests absorb carbon dioxide (CO₂) through photosynthesis and store the carbon in plant bodies, soil and forest products, thereby reducing the concentration of greenhouse gases in the atmosphere. Forest carbon stocks are usually categorized into the following carbon pools: above-ground biomass (AGB), below-ground biomass (BGB), soil organic carbon (SOC), dead wood and litter, which the carbon stock of trees is the sum of above-ground biomass and below-ground biomass.
To calculate the carbon storage of a tree, its diameter at breast height (DBH) and height (H) must first be measured, and the volume calculation formula is applied to determine the trunk volume. Then, using the wood density (D) of the tree species and the biomass expansion factor (BEF) or biomass conversion and expansion factor (BCEF), the biomass of the crown and branches are estimated, which gives the aboveground biomass. Next, the belowground biomass is estimated using the root-to-shoot ratio (R), and the total biomass is the sum of the aboveground and belowground biomass. Finally, the total biomass is converted into total carbon storage using the carbon factor (CF) and further converted to carbon dioxide to provide the final carbon sink estimate.

V＝（DBH）² ×0.79 ×H×F

V: tree volume (m³);

DBH: diameter at breast height (m);

H: tree height (m);

F: form factor, 0.5 for conifers, 0.45 for broad-leaved trees.

T_CO2= V × BCEF × (1+R) × CF × 44/12

T_CO2: carbon stock (tons of CO₂);

V: tree volume (m³);

BCEF: biomass conversion and expansion factor;

R: root-to-shoot ratio;

CF: carbon factor.

BCEF＝BEF×D

BEF：biomass expansion factor；

 D：wood density (ton/m³)。