The cellulose δ¹⁸O of plant tissues in peat is a potential climate proxy. However, understanding what is driving the shifts in δ¹⁸O of cellulose is required for its application. Here, we analyzed the δ¹⁸O values of Sphagnum and vascular plant cellulose, as well as the δ¹⁸O and δD values of pore water, in a 4-m-long peat core from the Bekanbeushi ombrotrophic bog to understand paleoclimatic changes in northern Japan over the past 2,000 years. The cellulose δ¹⁸O values of Sphagnum were lower than those of vascular plant tissues, although both draw water from the same layer. Whereas the cellulose δ¹⁸O values of Sphagnum more directly reflect those of precipitation, those of vascular plants become enriched through transpiration. Thus, the difference between vascular plants and Sphagnum (Δδ¹⁸O_vp–sp) is a potential proxy for relative humidity. Cellulose δ¹⁸O of Sphagnum revealed centennial variations with maxima around 800, 1300, and 1500 CE and minima around 500, 1000, 1700, and 1900 CE. The Δδ¹⁸O_vp–sp was inversely correlated with Sphagnum cellulose δ¹⁸O, indicating that the axis of summer westerlies was more frequently located to the north and the climate was moist in the former periods, whereas the axis of summer westerlies was generally located to the south and the climate was dry in the latter periods. These results suggest a warm and moist climate during the former periods due to frequent rainy summers driven by strong East Asian summer monsoon activity, and the opposite conditions in the latter periods.

中文翻译：

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泥炭核心中泥炭藓和维管植物的纤维素氧同位素揭示了过去 2000 年日本北部的气候变化

泥炭植物组织的纤维素 δ ¹⁸ O 是潜在的气候代表。然而，对于纤维素的应用，需要了解是什么驱动了纤维素δ ¹⁸ O的变化。在此，我们分析了δ ^18个的O值泥炭藓和维管植物的纤维素，以及所述δ ¹⁸ O和孔隙水的δD值，在从所述Bekanbeushi外围的冰原沼泽4米长的泥炭芯理解在北方气候环境变化日本过去2000年。泥炭藓的纤维素δ ¹⁸ O 值低于维管植物组织的纤维素δ ¹⁸ O 值，尽管两者都从同一层汲水。而泥炭藓的纤维素 δ ¹⁸ O 值更直接地反映降水，维管植物通过蒸腾作用变得丰富。因此，维管植物和泥炭藓之间的差异(Δδ ¹⁸ O _vp-sp ) 是相对湿度的潜在代表。泥炭藓的纤维素 δ ¹⁸ O显示百年变化，最大值在公元 800、1300 和 1500 年左右，最小值在公元 500、1000、1700 和 1900 年左右。Δδ ¹⁸ O _vp-sp与泥炭藓纤维素δ ¹⁸呈负相关O，说明夏季西风轴偏北较多，前期气候湿润，而夏季西风轴一般偏南，后期气候干燥。这些结果表明，由于东亚夏季风活动强烈而导致夏季频繁多雨，而在后期则相反，气候温暖潮湿。