Cell anatomy and leaf δ13C as proxies for shading and canopy structure in a Miocene forest from Ethiopia
Cell anatomy and leaf δ13C as proxies for shading and canopy structure in a Miocene forest from Ethiopia
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DOI：
10.1016/j.palaeo.2017.07.015
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发表时间：
2017-11-01
影响因子：
3
通讯作者：
Tabor, Neil J.
中科院分区：
文献类型：
--
作者：
Bush, Rosemary T.;Wallace, Jon;Tabor, Neil J.
植物化石通常是作为孤立的器官保存下来的，因此很难从化石中确定植物的生活习惯或生态系统结构。特别是，古生态学家一直在努力重建森林冠层结构，这是一个从根本上影响水文、营养循环和动植物生命的特征。利用细胞形态和叶片碳同位素组成的分析已经被提出来重建光状态，光状态本身就是冠层结构的代表，我们将这些代表应用于埃塞俄比亚中部中新世早期Mush山谷遗址保存完好的叶片化石。测定了豆科植物“豆科植物1号”21个叶化石的表皮细胞壁波动指数（波动指数，UI）和碳同位素值（δ C-13）。用同样的方法分析了另一种豆科植物形态种的5个叶片。碳同位素比率和总有机碳含量测量了85额外的化石叶片属于至少9个形态种。豆科植物1的叶片δ C-13和UI值都有很大的变化范围，这表明不同的叶片暴露在不同的光量下，这在封闭冠层森林中是可以预期的。然而，豆科植物1叶片的UI值与叶片δ C-13值不相关，这意味着这些变量中的一个或两个是由光照以外的因素驱动的。需要额外的现代校准来确定每项测量的关键环境变量，以及森林开口对保存的特征的影响。(C) 2017 Elsevier B.V.版权所有
Plant fossils are most commonly preserved as isolated organs, making it difficult to determine plant life habit or ecosystem structure from fossils. In particular, paleoecologists have struggled to reconstruct forest canopy structure, a character that fundamentally influences hydrology, nutrient cycling, and plant and animal life. Analyses utilizing cellular morphology and leaf carbon isotope composition have been proposed to reconstruct light regime, itself a proxy for canopy structure, and we apply these proxies to exquisitely preserved leaf fossils from the early Miocene Mush Valley site in central Ethiopia. Epidermal cell wall undulation (undulation index, UI) and carbon isotope values (delta C-13) were measured for 21 fossil leaves of a legume morphospecies, "Legume 1". Five leaves of a second legume morphospecies were also analyzed using the same procedures. Carbon isotope ratios and total organic carbon content were measured for 85 additional fossil leaves belonging to at least nine morphospecies. A large range of both leaf delta C-13 and UI values were obtained for Legume 1, indicating that different leaves were exposed to different amounts of light, as would be expected in a closed-canopy forest. However, Legume 1 leaf UI values do not correlate with leaf delta C-13 values, implying that one or both of these variables is driven by factors other than light exposure. Additional modern calibrations are needed to determine the key environmental variables for each measure, as well as the influence of forest openings on preserved signatures. (C) 2017 Elsevier B.V. All rights reserved.