晚中新世C<sub>4</sub>植被扩张与大气二氧化碳分压的关系

汪镇; 田军

doi:10.16562/j.cnki.0256-1492.2021032401

晚中新世C₄植被扩张与大气二氧化碳分压的关系

汪镇,
田军^,

同济大学海洋地质国家重点实验室，上海 200092

基金项目: 国家自然科学基金重点项目“探索晚新生代太平洋中深层经向翻转流与气候演变冰期旋回的关系”（42030403），“晚中新世大洋碳位移事件的成因机制及其古环境效应”（41776051）

详细信息

作者简介: 汪镇（1997—），男，硕士研究生，海洋科学专业，E-mail：1931663@tongji.edu.cn

通讯作者: 田军（1974—），男，教授，从事古海洋学与古环境变化研究，E-mail：tianjun@tongji.edu.cn

中图分类号: P532

收稿日期: 2021-03-24

修回日期: 2021-07-12

刊出日期: 2021-10-28

The Late Miocene C₄ vegetation expansion and its relation with the partial pressure of carbon dioxide in atmospheric

WANG Zhen,
TIAN Jun^,

State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China

More Information

Corresponding author: TIAN Jun, tianjun@tongji.edu.cn

Received Date: 24 March 2021

Revised Date: 12 July 2021

Publish Date: 28 October 2021

摘要

摘要:
大量陆地与海洋的地质记录证实了晚中新世C₄植被发生全球异步扩张，最早在10 Ma左右开始于非洲东部与西北部，随后8～6 Ma左右大范围传播至南亚、南非、北美等地区，最终C₄植被于上新世发生再次扩张，基本形成现今的生态格局。对于晚中新世C₄植被扩张的解释至今仍存在疑惑，主要围绕气候变化与CO₂展开争论。最新的大气二氧化碳分压（pCO₂）重建记录显示，大气CO₂浓度在晚中新世时期处于下降的趋势。综合考虑晚中新世C₄植被的扩张区域，地质记录重建的大气CO₂浓度与数值模拟实验中形成C₄植被扩张所需的大气CO₂浓度在数值上相吻合，突出了大气CO₂浓度变化对晚中新世C₄植被扩张的作用。由于现有的大气CO₂浓度重建记录的分辨率较低，不管是在趋势上还是数值上，其可靠性都有待商榷，未来应该专注于晚中新世可靠的高分辨率大气CO₂浓度记录的重建，这是解开晚中新世大气CO₂与C₄植被扩张关系的关键，对研究未来气候变化具有指导意义。
- C₄植被扩张 /
- 大气pCO₂ /
- 季节性气候 /
- 数值模拟 /
- 晚中新世
Abstract:
A large number of terrestrial and marine geological records has confirmed the global asynchronous expansion of C₄ vegetation in Late Miocene, which started in the eastern and northwestern Africa as early as 10 Ma, and then spread to South Asia, South Africa, North America and other areas in a wide range around 8～6 Ma. Finally, the C₄ vegetation expanded again in Pliocene, and the present ecological pattern is basically formed. However, the mechanism of the C₄ vegetation expansion in Late Miocene still remains unclear, with the major debate concentrating on climate and CO₂ changes. The recent atmospheric partial pressure pattern of carbon dioxide (pCO₂) reconstructed shows a downward trend of the atmospheric CO₂ concentration during Late Miocene. Considering the late Miocene C₄ vegetation expansion areas, the proxy-derived atmospheric pCO₂ is consistent with that needed for the C₄ vegetation expansion in a numerical simulation experiment, which highlights the role of the atmospheric pCO₂ in the Late Miocene C₄ vegetation expansion. The low time resolution of the existed proxy-derived atmospheric pCO₂ records determines their low reliability on both the long-term trend and the absolute values. The next step should focus on the reconstruction of the reliable high-resolution record of the atmospheric pCO₂ for Late Miocene, the key to unlock the relationship between the atmospheric pCO₂ and the C₄ vegetation expansion in Late Miocene, which has guiding significance for the study of future climate change.
- C₄ vegetation expansion /
- atmospheric pCO₂ /
- seasonal climate /
- numerical simulation /
- Late Miocene

HTML全文

图 1 实验模拟与地质记录揭示的晚中新世C₄植被扩张范围

Figure 1.

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图 2 大气pCO₂、C₄植被扩张和晚中新世大洋碳位移事件

Figure 2.

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图 3 C₃/C₄植被参与的全球碳循环过程^[60]

Figure 3.

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图 4 C₄植物的CO₂浓缩机制^[27]

Figure 4.

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图 5 降雨量、季风强度、火灾强度、C₃/C₄植被比例的替代性指标

Figure 5.

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表 1 古大气pCO₂的重建方法

Table 1. Methods for reconstruction of ancient atmospheric pCO₂

方法	相关公式	说明	参考文献
古植物叶片的气孔指数		实验培养的银杏气孔指数SI与CO₂浓度的经验关系	Retallack, et al^[36]
古土壤碳酸盐的碳同位素		S（z）是深度为z的土壤生物呼吸产生的CO₂浓度，δ¹³C_s、δ¹³C_r、δ¹³C_a分别是土壤总CO₂、土壤生物呼吸产生CO₂、大气CO₂的碳同位素组成	Cerling, et al^[37]
浮游藻类生物标志物的碳同位素		ε_p为总碳同位素分馏值，b为所有影响总碳同位素分馏的生理作用值，ε_f为碳固定过程的分馏系数	Jasper, et al^[40]
浮游有孔虫壳体的硼同位素		K_B^*、α_B是硼酸反应的电离常数与分馏系数，δ¹¹B_T是海水总硼的硼同位素组成，δ¹¹B_B(OH)₄^-是海水硼酸根的硼同位素组成；求[CO₂]还需结合碳酸盐体系第二个参数	Zeebe, et al^[43]

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