It does, but if it is young wood it contains newly captured carbon and so the net effect over a short time period (in climate terms) is that it doesn't change t

It does, but if it is young wood it contains newly captured carbon and so the net effect over a short time period (in climate terms) is that it doesn't change the overall atmosphere. In comparison to coal or other fossil fuels, which adds tons of carbon that had previously been outside the atmosphere, a net zero over 50 years is pretty green. Of course, this supposes you actually manage to get enough new trees grown in that time which might not be true if forests are logged by clear cutting and not supported after that.