Yes, seasonal trees cause measurable changes in the amount of co2 and oxygen in earth’s atmosphere.

Here is a graph of carbon dioxide in the atmosphere over time. The long term trend is due to humans, but the yearly wiggles are due to trees. Every summer they grow and pull down CO2 into their bodies, and every winter they decay and release that CO2. (You may wonder why the northern and southern hemispheres don’t cancel each other out. Answer: there are fewer trees experiencing winter in the south.)

And here is a graph of oxygen showing exactly the opposite trend, for exactly the same reasons. An important note: we are not going to run of oxygen. Because there’s so much oxygen in the air, the changes are relatively tiny: human activity has reduced it by about 0.08 %.