Trees store carbon through the process of photosynthesis. Using energy from the sun the trees change carbon dioxide and water into glucose and oxygen. The glucose is then used by the plants to make more complex carbohydrates such as cellulose which is an important component of plant cell walls. Wood is about 40% cellulose. Photosynthesis can be represented using the chemical equation 6CO2 + 6H2O → C6H12O6 + 6O2. Each Glucose molecule (C6H12O6) contains 6 carbon atoms and is the basic building block of many of the more complicated molecules found in trees. Very generally about 65% of a tree is dry biomass and 50% of this biomass is carbon. 20% of the tree’s biomass is below ground in the roots.
Leys, A. J. (n.d.). How carbon is stored in trees and wood products. Retrieved from Forest Learning Australia: https://forestlearning.edu.au/images/resources/How%20carbon%20is%20stored%20in%20trees%20and%20wood%20products.pdf