This is a fairly wonderful thing to know.
"Every day a forty foot tree takes up fifty gallons of dissolved nutrients from the soil, raises the mixture to the top of the tree. In the process it converts the nutrients into ten pounds of carbohydrates and releases sixty cubic feet of oxygen into the atmosphere." From Nature Speak by Ted Andrews.
Now imagine a whole forest doing the this every day. Next time you see a tree thank it for the gifts of the air be breath, the shade for the leaves, the wonderful scent in spring.