But when a plant dies, its decay, in chemical reactions equivalent to burning all its carbonaceous materials, would use up an amount of oxygen equal to all the oxygen released by that plant during its lifetime. There would therefore be no net gain in atmospheric oxygen, but for one thing. Not all dead plants decay completely. Some parts of them are laid down as coal (or equivalents), other parts are consumed and bits of the consumers themselves may become locked into rocks.* The net effect is to store energy-rich compounds underground and leave some oxygen free to circulate. Releasing some of
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