Negative δ18O–δ13C relationship of pedogenic carbonate from northern China indicates a strong response of C3/C4 biomass to the seasonality of Asian monsoon precipitation
Negative δ18O–δ13C relationship of pedogenic carbonate from northern China indicates a strong response of C3/C4 biomass to the seasonality of Asian monsoon precipitation
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DOI：
10.1016/j.palaeo.2011.12.007
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发表时间：
2012-02
期刊：
影响因子：
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通讯作者：
Shiling Yang;Z. Ding;Xu Wang;Zihua Tang;Z. Gu
中科院分区：
文献类型：
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作者：
Shiling Yang;Z. Ding;Xu Wang;Zihua Tang;Z. Gu
评估未来气候变化对东亚C3/C4生物量的影响在很大程度上取决于对过去C3/C4变化与亚洲季风环流之间关系的理解。C3/C4生物量的冰期-间冰期变化很容易被归因于夏季风。然而，控制C3/C4植被与亚洲季风联系的内部过程还没有被清楚地描述。本文介绍了中国北部全新世、末次和倒数第二次间冰期的成壤碳酸盐的同位素结果。砂砾质土壤现代碳酸盐的δ18O测定值与预测值的对比表明，土壤碳酸盐主要形成于温暖的雨季。中国黄土碳酸盐结核表现出明显的负δ~(18)O-δ~(13)C关系，其同位素分布在南部黄土高原大于北部黄土高原。结合降雨量、降水δ~(18)O和C3、C4植物代谢峰，建立了一个解释碳酸盐结核同位素特征的概念模型。我们的模型表明，特定地点的季风降水狭隘集中的季节产生低δ18O值的土壤水，同时有利于C4植物而不是C3植物。我们的模型进一步表明，土壤碳酸盐的分散同位素值反映了较强的夏季风，而集中的值反映了较弱的夏季风。土壤碳酸盐的δ~(13)C值显示末次间冰期C4植被向北增加的显著格局，而倒数第二次间冰期和全新世则呈现平坦的空间格局。推测末次间冰期夏季风比倒数第二次间冰期和全新世强，导致C3森林生态系统北移至黄土高原南部。此外，结核内δ13C和δ18O值之间的同相关系表明，C3/C4生物量对亚洲季风降水的季节性有强烈且可能快速的响应。在这种情况下，如果将最后的间冰期(MIS5)作为预测不久的未来的类比，那么C3植物可能在南方受到青睐，而C4植物在北方可能是有效的。
Evaluating how future climate changes may impact C3/C4biomass in East Asia depends largely on the understanding of the relationship between past C3/C4variations and Asian monsoon circulation. The glacial–interglacial variations in C3/C4biomass have been readily ascribed to the summer monsoon. However, the internal processes governing the link of C3/C4vegetation to the Asian monsoon have not been clearly described. Here we present isotopic results of pedogenic carbonate from northern China for the Holocene, the last and penultimate interglacial periods. Comparison of the observed and predicted δ18O values of modern soil carbonate from gravelly soils suggests that pedogenic carbonate forms mainly in warm, rainy season. Carbonate nodules from the Chinese loess demonstrate a distinct negative δ18O–δ13C relationship and a wider scatter of isotopic values in the southern Loess Plateau than in the northern part. By combining rainfall, δ18O of precipitation and the peak of C3and C4plant metabolism, we develop a conceptual model to explain the isotopic signatures of the carbonate nodules. Our model shows that a narrowly-focused season of monsoon precipitation at a specific site produces low δ18O values of soil water and simultaneously favors C4over C3plants. Our model further suggests that the scattered isotopic values of soil carbonate reflect a strong summer monsoon while the focused values indicate a weak summer monsoon. δ13C values of soil carbonate indicate a striking pattern of northward-increasing C4vegetation for the last interglacial, while a flat spatial pattern is seen for the penultimate interglacial and the Holocene. It is inferred that the summer monsoon was stronger during the last interglacial than during the penultimate interglacial and the Holocene, leading to a northward displacement of C3forest ecosystems into the southern Loess Plateau. In addition, an in-phase relationship between intra-nodule δ13C and δ18O values suggests a strong and possibly rapid response of C3/C4biomass to the seasonality of Asian monsoon precipitation. In this context, if the last interglacial period (MIS 5) is taken as an analog for the projected near future, then C3plants may be favored in the south while C4plants may be efficient in the north.