By Martin Hodson

In recent years there has been much work on the possibility that carbon could be sequestered in phytoliths and contribute to solving global warming.1, 2 There have been a number of calculations of how much is sequestered globally. The crucial figure in these calculations is the concentration of carbon in the phytoliths that is used, so-called phytolith occluded carbon. These figures are derived from phytoliths that have been acid digested or dry ashed at 450-500oC. Values vary from less than 0.1% to 6% depending on the technique used. But are any of these measurements realistic? In native unprocessed material the lemma macrohair from Phalaris canariensis contained 40% silica, 55%, polysaccharides and 5% proteins.3 At maturity these hairs consist entirely of wall material. I know of no data for lumen deposits, which undoubtedly have a higher percentage silica in the native state. Some of the carbon in both cell wall and lumen phytoliths cannot be accessed by hot acid or dry ashing. I suspect that more carbon is inaccessible to breakdown processes in soil than is estimated by our “occluded carbon” determinations. My question is whether these measurements are a good estimate of what is present in soil phytoliths?


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Martin Hodson



Published: 18 Sep, 2016

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