system
Given the following post, respond as if you're commenting on Reddit:
human
What are trees made of? Do they remove mass from the ground they are planted in at all (besides water)?

I don't understand how trees work. You plant a seed, water them, and they grow using nutrients from the ground. But they can turn into huge redwood trees with massive weight. Do they remove mass from the ground while growing? If not, what about when they die, do they add mass after they decompose?
gpt
>What are trees made of? 

The same as the rest of life - primarily Carbon, Hydrogen, Oxygen and Nitrogen (plus Phosphorus, sulphur, and lesser amounts of many other elements). This is mostly in the form of hydrocarbons like cellulose; also water, and then smaller amounts of amino acids and sugar, dissolved minerals and other materials. When you burn wood you are mainly burning cellulose.

>Do they remove mass from the ground while growing? 

Yes, a little in the form of elements like Nitrogen and Phosphorus which they cannot easily get from the atmosphere. But *in the main* they get their mass from the air. The air is full of CO2. Trees photosynthesise by converting CO2 and H20 into glucose and oxygen. So they *create hydrocarbons* from the air. A large chunk of the physical hard wood of the tree comes directly from the gases in the atmosphere.

>what about when they die, do they add mass after they decompose?

Yes. Coal in the ground comes from the mass of decayed plant matter that took its mass from the atmosphere. Earth's early atmosphere was much higher in CO2.