My simplistic model for the carbon cycle was that plants (or trees in particular) photosynthesise and transpire. The former takes up CO2 and H2O and the latter does the reverse but obviously not netting out. The carbon for the cellular material (in particular wood) comes entirely from atmospheric CO2 (?).
The mass of trees comes mainly from cellulose which is roughly 50% carbon. Therefore the mass of sequestered CO2 is simply related to the mass of trees, with the proportion equal to the ratio of the molecular masses of cellulose and CO2 with balanced carbon content. Wiki says cellulose is some sort of sugar type thing (C6H10O5)n and carbon dioxide is obviously CO2 so the ratio is something like: for each kilo of tree/wood grows 1.62 kg of CO2 is sequestered?
Is this completely wide of the mark?