摘要
大量陆地与海洋的地质记录证实了晚中新世C_(4)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C_(4)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C_(4)植被扩张的解释至今仍存在疑惑,主要围绕气候变化与CO_(2)展开争论。最新的大气二氧化碳分压(pCO_(2))重建记录显示,大气CO_(2)浓度在晚中新世时期处于下降的趋势。综合考虑晚中新世C_(4)植被的扩张区域,地质记录重建的大气CO_(2)浓度与数值模拟实验中形成C_(4)植被扩张所需的大气CO_(2)浓度在数值上相吻合,突出了大气CO_(2)浓度变化对晚中新世C_(4)植被扩张的作用。由于现有的大气CO_(2)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CO_(2)浓度记录的重建,这是解开晚中新世大气CO_(2)与C_(4)植被扩张关系的关键,对研究未来气候变化具有指导意义。
A large number of terrestrial and marine geological records has confirmed the global asynchronous expansion of C_(4) 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 C_(4) vegetation expanded again in Pliocene, and the present ecological pattern is basically formed. However, the mechanism of the C_(4) vegetation expansion in Late Miocene still remains unclear, with the major debate concentrating on climate and CO_(2) changes. The recent atmospheric partial pressure pattern of carbon dioxide(pCO_(2)) reconstructed shows a downward trend of the atmospheric CO_(2) concentration during Late Miocene. Considering the late Miocene C_(4) vegetation expansion areas, the proxy-derived atmospheric pCO_(2) is consistent with that needed for the C_(4) vegetation expansion in a numerical simulation experiment, which highlights the role of the atmospheric pCO_(2) in the Late Miocene C_(4) vegetation expansion. The low time resolution of the existed proxy-derived atmospheric pCO_(2) 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 pCO_(2) for Late Miocene, the key to unlock the relationship between the atmospheric pCO_(2) and the C_(4) vegetation expansion in Late Miocene, which has guiding significance for the study of future climate change.
作者
汪镇
田军
WANG Zhen;TIAN Jun(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China)
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2021年第5期160-172,共13页
Marine Geology & Quaternary Geology
基金
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)。
