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In page Terrestrial biological carbon cycle:

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The carbon cycle is an essential part of life on Earth. About half the dry weight of most living organisms is carbon.[citation needed] It plays an important role in the structure, biochemistry, and nutrition of all living cells. Living biomass holds about 550 gigatons of carbon,[1] most of which is made of terrestrial plants (wood), while some 1,200 gigatons of carbon are stored in the terrestrial biosphere as dead biomass.[2]