While living trees do take up carbon dioxide from the atmosphere, they also give off some by doing cellular respiration and photorespiration. The greater production of carbon dioxide is from dead trees decomposing, which give off carbon dioxide as fungi and other microbes digest them and perform cellular respiration.
Work Step by Step
While this chapter talks a lot about plants, this question asks you to review Ch. 9 and to think about not only plants but about cellular respiration in other organisms as well.