# Is the net amount of CO2 sequestered by trees from the atmosphere simply related to the mass of new growth?

My simplistic model for the carbon cycle was that plants (or trees in particular) photosynthesise and transpire. The former takes up $$\small\mathsf{CO_2}$$ and $$\small\mathsf{H_2O}$$ and the latter does the reverse but obviously not netting out. The carbon for the cellular material (in particular wood) comes entirely from atmospheric $$\small\mathsf{CO_2}$$ (?).

The mass of trees comes mainly from cellulose which is roughly 50% carbon. Therefore the mass of sequestered $$\small\mathsf{CO_2}$$ is simply related to the mass of trees, with the proportion equal to the ratio of the molecular masses of cellulose and $$\small\mathsf{CO_2}$$ with balanced carbon content. Wiki says cellulose is some sort of sugar type thing $$\small\mathsf{(C_6H_{10}O_5)n}$$ and carbon dioxide is obviously $$\small\mathsf{CO_2}$$ so the ratio is something like: for each kilo of tree/wood grows 1.62 kg of $$\small\mathsf{CO_2}$$ is sequestered?

Is this completely wide of the mark?

• For a given species of tree or plant, then yes, the mass of sequestered CO2 should be roughly proportional to the mass of the tree. I think there's some variation between species. – Semidiurnal Simon Aug 2 '19 at 0:40
• A lot of the mass of a living plant is actually water, and that's going to vary a lot between species, and even different parts of the tree. (Consider the weight difference between green wood and seasoned firewood, for instance.) But if you can get dry weight, then I think it should be close. – jamesqf Aug 2 '19 at 17:46