Not really, unless the resulting carbon somehow gets stored underground (e.g. trees become coal). Even carbon from soil eventually gets released (by bacteria) or reused (by other plants).
Really, the only question is the biomass of trees. 1MT trees left to grow for 100 years == 2MT of trees harvested every 50 years.
You're only looking at the deltas of carbon in/out. I am referring to the absolute amount of carbon stored per area. Older forests -> higher soil carbon and larger trees
Really, the only question is the biomass of trees. 1MT trees left to grow for 100 years == 2MT of trees harvested every 50 years.