Study on phytolith-occluded organic carbon in soil of subtropical forest of Southen Zhejiang

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    Phytolith-occluded organic carbon (PhytOC) is a stable form of organic carbon. PhytOC is a product of silicification of a plant per se and goes back into the soil after the plant dies or withers, thus affecting storage of the stable carbon pool in the forest eco-system. Soil samples were collected from four different soil layers (0~10 cm, 10~30 cm, 30~60 cm and 60~100 cm) in soil profile under five different stands of typical subtropical forestin Qingyuan County, Zhejiang Province for analysis of effects of the forest stands on content of soil phytolith and PhytOC and distribution of PhytOC, and for estimation of total storage of soil PhytOC in these forest soils, separately. In this study phytolith in soil samples was isolated using the microwave digestion method, and complete removal of peripheral organic carbon from phytolith was validated with the Walkley-Black method. The isolated phytoliths were put into a centrifuge tube with a known mass and dried in a forced air oven at 75℃ for 24 h. After cooling down the sample was weighed to determine mass of the phytoliths. Determination of PhytOC was performed using the Alkali Dissolution-Spectrophotometry. At the same time, a portion of standard soil sample (GBW07405) was added to verify accuracy of the measurement. Results show that the content of phytoliths varied with the type of forest soil and the mean content of PhytOC in phytoliths did, too. The content of Phytoliths in the soil was 19.73 g kg-1 under bamboo groves, 8.14 g kg-1 under Masson pine forest and 12.24 g kg-1 under broad-leaved forest, showing sharp difference between the three. The mean content of PhytOC in soil phytoliths was 24.31 g kg-1 under Masson pine forest and 13.06 g kg-1 under conifer forest, also displaying sharp difference. The content of soil PhytOC under the same forest stand varied with depth in soil profile and the variation trends differed from stand to stand. The content of soil PhytOC decreased with soil depth under Moso bamboo groves and Chinese fir forest and did in a certain degree, too, under the other forest stands. PhytOC/TOC in the soil increased dramatically with soil depth under all the forest stands, except for the stand of Masson pine. The total storage of PhytOC in the soil under Moso bamboo groves, Chinese fir forest, Masson pine forest, broadleaf forest and mixed conifer-broadleaf forest was 1.988×107, 4.025×107, 2.575×107, 2.542×107 and 0.340×107 t. To sum up, soil phytoliths under the five different stands of forest vary in the range between 8.14 and 19.73 g kg-1, and the content of soil phytoliths is significantly higher under bamboo groves than under the other four stands of forests. The content of PhytOC in phytoliths varies between 13.06~24.31 g kg-1, and is the highest under the Masson pine forest. The content of soil silicon is positively related to content of soil PhytOC, suggesting that to raise the content of soil silicon is conducive to the content of soil phytoliths and soil PhytOC. The content of Phytoliths decreases with soil depth and on the whole, the content of soil PhytOC decreases with soil depth along a soil profile, while PhytOC/TOC rises dramatically with soil depth but not so obvious in the soil layers of 10~30 cm and 30~60 cm under Chinese fir forest and broadleaf forest.

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Lin Weilei, Ying Yuqi, Jiang Peikun, Huang Zhangting, Wu Jiashen, Meng Cifu. Study on phytolith-occluded organic carbon in soil of subtropical forest of Southen Zhejiang[J]. Acta Pedologica Sinica,2015,52(6):1365-1373.

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  • Received:September 26,2014
  • Revised:April 17,2015
  • Adopted:June 30,2015
  • Online: August 31,2015
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