It is one of the uncertainties. But keep in mind that plant growth is seasonal and a lot of the CO2 is released. There will be more wood and other sequestered carbon but I think it is very poorly measured. The CO2 rise in the atmosphere is about half of what it should be given man's 30 Gt (CO2) per year. The rest is assumeed to be mainly in the ocean but could also be in increased woody plant growth.
Where do you go to get the data and information you trust?