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B-6.2.3 Quantitative Analysis of Soil Organic Carbon Turnover by Using Natural Abundance of Carbon Isotopes

[Contact Person]

Tadakatsu Yoneyama
Plant Nutrition Diagnosis Laboratory,
National Agriculture Research Center,
3-1-1 Kannondai, Tsukuba, Ibaraki 305-8666, Japan
Tel: +81-298-38-8814, Fax: +81-298-38-8814,
e-mail:yoneyama@narc.affrc.go.jp

Total Budget for FY 1996-FY 1998

7,485,000 Yen FY 1998 2,493,000 Yen

Abstract

The carbon content and natural ¹³C abundance (δ¹³C) of soil organic carbon from Japan, the Philippines and Thailand were successfully analyzed by on-line ANCA-SL mass spectrometer. Japan soils from cultivated fields had (δ¹³C values of -24%o from Hokkaido, -22%o 〜-18%o from Main Island, Shikoku and Kushu, suggesting some C input by C₄, plants (highly likely by Miscanthus sinensis). In Miyako Island, the Philippines, and Thailand, transfer to sugarcane cultivation from forests markedly decreased C content and increased δ¹³C values of soil organic carbon from C₃ plants-derived carbon (-27%o 〜 -24%o) to C₄-dominant carbon (-17%o 〜-14%o) within 25 years in Miyako Island, 10 〜 50 years in the Philippines, and 8 〜 20 years in Thailand.

[Key Words]

Natural ¹³C abundance (δ¹³C), Carbon isotopes, Soil organic,carbon, Carbon turnover. C₃ plant, C₄ plant