You're correct, but only if the tree's entire carbon store is released to the atmosphere, such as by being burned. Not all of the tree is able to decay and release its carbon. The portion of the organic matter that fell to the forest floor, was covered by other organic matter, stayed there for a long time and eventually becomes coal or oil. In other words, you can end up storing a lot of carbon in the soil.
I suppose one good way to sequester carbon is to plant trees then cut them down at maturity and build durable buildings out of them.
I suppose one good way to sequester carbon is to plant trees then cut them down at maturity and build durable buildings out of them
Or dump the trunks into any oxygen starved bog.
Or ship them to the northern parts of the world and bury them in the shallow permafrost layer.
Except both of those hold the risk of a sudden return of massive amounts of CO2 to the air due to some unforeseen (fire!) event.
The most low risk is probably to turn them into charcoal, mix that charcoal into the soil they came from and plant new trees there. As long as some of the carbon is still in the soil by the time you repeat the process, you have a net gain of CO2 sequestration.
I suppose one good way to sequester carbon is to plant trees then cut them down at maturity and build durable buildings out of them.