Roger DuBose, age 15, of Eugene, Oregon, for his question:

Do younger or older trees produce more oxygen?

Age may or may not be related to the oxygen output of a tree. This depends upon the total area of its green leaf surface, plus multiple other factors. The oxygen output is a by product of photosynthesis, carried on by green chlorophyll. This complex process requires carbon dioxide and water, plus the energy from certain wavelengths of solar radiation. Most large trees with lots of greenery are older, but not all of them. In any case, photosynthesis stops at sunset and no deciduous trees yield oxygen during the winter. Operations also slow down when the soil is dry and the carbon dioxide is below normal.

Hence, a tree's oxygen output depends less on its age and more on its size, greenery and these other factors. What's more, every species prefers its own temperature range and many slacken down at midday when the summer sunshine is most intense. As a rule, trees do their best during the growing season, when the soil is moist and the carbon dioxide in the air is somewhat above normal. Under the best conditions, regardless of age, the trees with more greenery yield more oxygen