@article{oai:nagoya.repo.nii.ac.jp:00019792, author = {中原, 誌公 and Zou, P. and 安藤, 豊 and Fu, J. and Cao, Z. and 渡邉, 彰 and Nakahara, Shiko and Zou, Ping and Ando, Ho and Fu, Jianrong and Cao, Zhihong and Watanbe, Akira}, journal = {名古屋大学加速器質量分析計業績報告書}, month = {Mar}, note = {The effect of long term use as a rice paddy field on the stability of soil organic C (SOC) was investigated using the plow layer soils collected from two series of rice fields distributed in Hangzhou Bay region, Zhejiang Province, China, which have the estimated periods of time under irrigated rice paddy ranging from 5 to 2000 years. Amount, C and N stable isotopic ratios (δ13C and δ15N), and 14C age were compared mainly for the silt/clay sized fractions of soils and their humin as representative soil organic matter (SOM) fractions with a relatively long residence times due possibly to the adsorption to clay minerals and insolubility in water. The degree of humification of humic acids in silt/clay was also determined. Total C and humin C in the silt/clay fraction increased with increasing estimated period under rice paddy up to 2000 years. The degree of humification of humic acids increased during the first 100 years, but did not change afterward, suggesting that the structural change to refractory substances was not responsible for the enhanced SOC accumulation. A gradual decrease in δ15N suggested the increase in the contribution of organic N fixed recently or derived from fertilizer to total silt/clay N and humin. The 14C age of humin became younger with increasing estimated period under rice paddy, which suggested that the larger SOC in the soils used as rice paddy field for a longer time was owing to the enhanced accumulation of organic C recently assimilated., 中国浙江省の杭州湾湾岸域に分布する推定水田利用年数5~2000年の土壌を用いて、長期的な水田利用が土壌有機炭素の安定性に与える影響を調べた。相対的に粘土鉱物への吸着と不溶性であることから相対的に滞留時聞が長いと考えられるシルト/粘土画分およびそのヒューミン画分に着目して蓄積量、炭素および窒素自然安定同位体比(δ13C、δ15N)および14C年代を比較した。また、フミン酸の黒色度と推定水田利用年数との関係も調べた。シルト/粘土に蓄積している全C量およびヒューミンC量は推定水田利用年数が長い土壌ほど高い傾向を示した。フミン酸の黒色度は推定水田利用年数100年まで増大したが、それ以降は変化が無く、腐植化の進行による難分解構造への変化が有機C蓄積量の増大の原因ではないことを示唆した。一方、δ15Nは水田利用年数1000年から2000年にかけて低下し、肥料由来Nや固定されてからの年数が短い有機Nの蓄積が進んでいる可能性を示唆した。同様にヒューミンの14C年代は推定水田利用年数が長い土壌ほど若く、新しい有機物の蓄積量の増大が全C量の増大に寄与していることが示された。, 名古屋大学年代測定総合研究センターシンポジウム報告}, pages = {62--68}, title = {長期水田利用下で蓄積した土壌有機炭素の安定性}, volume = {25}, year = {2014} }