Trees Feasting on Sky, Drinking the Earth.

 Have you ever wondered why you don't see pits in the ground around every big tree?  Skiers know about snow pits around trees but the big question is "Where the heck did all that wood come from?  Where are the dirt pits?"

Trees eat sky.  The wood is made of cellulose which is made of carbon, oxygen and hydrogen.  The carbon doesn't come from the earth.   Carbon is consumed from the sky.  A forest doesn't go hunting for its dinner.  It eats the air that comes to it freely, sucking it in through every leaf pore, packing away the carbon from the trace carbon dioxide and leaving the oxygen part  of the CO2 to drift further.

The dinner menu according to Wikipedia : 
(Note how tiny the edible portion is, 0.04% and almost two thirds of those table crumbs is the oxygen part of the CO2.).  While some of our colleagues are frantic about excess CO2, our green brethren are full of joy at the feast and in fact crops we plant are up and forest volumes expanding. (A related article here at carbonbrief.org.)

By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide

The composition of wood: 

The chemical composition of wood varies from species to species, but is approximately 50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements .. by weight.

The formula for cellulose:

        Chains of C6H10O5