[mech987876]

While the trees are alive they sink the amount of carbon present within them.

[graemep]

but a natural forest has trees in all stages: growing, mature, dead and decaying.

What you are saying implies this is not a sink.

[mech987876]

I'm not particularly strict on the terminology of whether a carbon sink is permanent or not (in my usage above it is not permanent). But yeah we are on the same page regarding the life cycle of a tree now so it is clear.