This week's question comes from Holly Irving in Lake Echo Nova Scotia. She asks: Which trees of the same age or size provide us with the most oxygen over the course of a year, deciduous or evergreen?

Ever wonder what happens to oxygen levels when leaves fall off the trees? Joe lets us know how we are still able to breathe.

As winter fades (quite rapidly this year) and spring emerges, trees undergo a fascinating transformation, signaling a new cycle of life. During winter, trees lie dormant, conserving energy and waiting ...

Dr. Universe: Do trees still create oxygen and clean the air after their leaves fall off? – Nova, 8, Palouse, Wash. The trees that lose their leaves in fall, such as chestnuts, oaks, aspens and maples ...