[U-02] 人新世・第四紀の気候および水循環

[U02-P09] Surface Peat Accumulation Rates Estimated Using Multiple Radionuclide Analyses in a Plateau Wetland, Eastern Hokkaido, Japan

*常岡 廉^1,2、坂下 渉³、近藤 玲介^1,4、横山 祐典^1,2 (1.東京大学 大気海洋研究所、2.東京大学大学院 理学系研究科 地球惑星科学専攻、3.国立研究開発法人 森林研究・整備機構 森林総合研究所、4.北海道大学大学院 農学研究院 農業土木学研究室)

キーワード：湿原、炭素蓄積速度、泥炭蓄積速度、鉛-210年代測定法、セシウム-137、放射性炭素

Peat accumulation rates in wetlands on plateaus, where sediment supply from rivers is minimal, have been rarely documented. However, evaluating the carbon storage potential of peatlands is crucial for understanding the global carbon cycle. In this study, we used multiple isotopes (Lead-210, cesium-137, and radiocarbon (¹⁴C)) to examine surface peat accumulation on a plateau in eastern Hokkaido, Japan. Our findings indicate that the constant rate of supply model, when corrected for the ¹⁴C bomb peak, can provide reliable accumulation rate estimates. The upper 13 cm of the peat layer accumulated over the past 70 years, with mean accumulation rates of 8.1 ± 3.2 mm yr^-1 in the acrotelm and 1.3 ± 0.5 mm yr^-1 in the catotelm. Comparisons with a previous study suggest that peat accumulation rates remained consistent across the study area in the absence of external disturbances. Furthermore, our estimated carbon accumulation rates (CARs) were 110 ± 37 gC m^-2 yr^-1 in the acrotelm and 33 ± 9 gC m^-2 yr^-1 in the catotelm, providing a valuable reference for decadal-scale CAR in the East Asian monsoon region.