You don't HAVE to make it into charcoal, but it will take up way more volume if you don't and contains tons of volatiles like methane that will come out and may make the ground less stable to simply bury with dirt as it partially rots.

Theoretically you could harness some of those volatiles for some energy production, but at the very least use those volatiles to heat the wood and make it charcoal for basically free.

Charcoal is like 80% carbon and the tree extracted it from the atmosphere.