3 ms·

Dry wood is about 50% carbon, 41% oxygen, 6% hydrogen, and 3% trace minerals, so it's probably safe to say that over 50% of it comes from CO2, and the rest from

• mahogany 6y ago
  Is there not carbon in the soil? Edit: I misread what you said. I think you are claiming that because there is so much carbon and oxygen, probably more than half comes from CO2. But there is both carbon and oxygen (well really, air) in soil. Although apparently the concentration of CO2 in the soil's air is much higher than it is in the normal atmosphere, so it's possible your statement is correct. (Plus looking at dry wood composition is a bit odd when it's generally less than 15% moisture content - that leaves out a lot of water that's present in a living tree.)
  • Pfhreak 6y ago
    Dry mass is typically used because it's consistent. Trees fluctuate over the year, being drier in some seasons than other. But they'll have the same dry mass. Trees are mostly C6 H10 O5, coming from CO2 and H20. Based on atomic weight about 70% of the mass of the dry wood comes from CO2. Fresh wood will have extra water content, taken from the soil (though that water came from the air too). There is carbon in the soil, but most plants don't take carbon up from their roots meaningfully. Nitrogen, phosphorus, potassium, and other trace minerals. Decomposers like fungi, bacteria, and insects will eat the carbon in the soil and release CO2.