How does burning wood change the carbon cycle?

The carbon based glucose molecules found in the cellulose fibers of the wood will be turned into water and Carbon Dioxide in the normal Carbon cycle. Burning the wood will cause this reaction to happen very quickly in an environment.

When a tree dies. decomposers start to break down the Carbon based molecules in the tree. Algae, fungus, ants, termites bacteria and other decomposers, metabolize the Carbon based molecules. The resulting products of the decomposition are water and Carbon Dioxide just as in all forms of cellular respiration. The decomposition of a large tree can take decades, it is a slow process.

Burning the wood has the same net effect as decomposition. The rapid Oxidation of the wood in burning releases the products of water and Carbon Dioxide, the same products as cellular respiration. The difference is that the same same large tree can be reduced and the Carbon Dioxide released back into the atmosphere in a matter of hours.

Burning wood changes only the rate at which the Carbon cycle occurs, in reducing the wood back into Carbon Dioxide.