Question: Do leaves on trees make oxygen? If they do during the winter when the leaves fall off the trees is there less oxygen in the air?

Gabriele De Chiara answered on 12 Nov 2013:

Yes, leaves on trees produce oxygen through photosynthesis. In autumn days become shorter and trees prepare for winter by letting leaves fall. In winter there will not be enough light for photosynthesis and trees will consume food from the ground. Technically yes there is less oxygen, however because of winds the atmosphere is always mixed and oxygen from other regions will be available. Also remember that there are evergreen trees like pines that do not lose leaves in winter.