The Devonian mass extinction: cataclysm or death by a thousand cuts?

泥盆纪大灭绝：灾难还是千刀万剐？

• 批准号: NE/V001639/1
• 负责人: Charles Wellman
• 金额: $ 82.4万
• 依托单位: University of Sheffield
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV001639%2F1
• 关键词: Devonian; mass; extinction; cataclysm; death

Complex multicellular life first appeared on Earth some 800 million years ago and subsequently diversified through a bewilderingly complex pattern of species originations/extinctions. However, this was not a steady and uninterrupted process. On at least five occasions the biota of the planet was devastated by a catastrophe that eliminated a considerable proportion of total biodiversity--including entire groups of organisms (higher taxa). These so-called 'mass extinctions' fundamentally changed the nature of life on Earth by steering evolution into a completely different trajectory.Of the 'Big Five' mass extinctions by far the least understood is the Devonian mass extinction that occurred ca.370 million years ago. There is widespread debate regarding both the timing and nature of this event, which has led to a complete lack of consensus regarding its causes. This proposal seeks to investigate the Devonian mass extinction from a fresh perspective focussing on changes in carbon-cycling.The Earth currently has two carbon-cycles of similar magnitude: a marine one based on photosynthetic plankton and a terrestrial one based on photosynthetic land plants. Fundamental changes in carbon-cycling took place during the Devonian due to dramatic changes in the nature of terrestrial vegetation. At the start of the Devonian land plants were centimetres tall, rooted in very shallow soils and covered a limited area of the continents. By the end of the Devonian vast swathes of the continents were shrouded in forests of trees tens of metres tall that deep-rooted into mature soils. These major vegetation changes caused profound changes in the terrestrial carbon-cycle (due to carbon sequestration from chemical weathering and biomass burial). We hypothesise that it was dramatic changes to the terrestrial carbon-cycle that disrupted the Earth system and caused the Devonian mass extinction. However, we believe that it was not a single catastrophic event (such as the bolide impact that caused the end Cretaceous mass extinction) but rather it occurred sequentially as discrete morphological/anatomical innovations led to changes in plant size and coverage causing step-changes in the terrestrial carbon-cycle.The research project will focus on the Devonian sequences of northern Spain. These are ideal because they: (i) are remarkably complete and incorporate known extinction events at the Frasnian-Famennian and Devonian-Carboniferous boundaries; (ii) accumulated in isolation on a large microcontinent and as such are not influence by species immigration/emigration and habitat tracking; (iii) contain an excellent fossil record of both marine plankton (acritarchs and chitinozoans) and terrestrial vegetation (plant spores/pollen).We will study the evolutionary dynamics of both the marine plankton and terrestrial vegetation through a study of species origination/extinction patterns. This biodiversity profile will be integrated with geochemical analyses that will identify perturbations in the Earth's carbon-cycle (in addition to nutrient cycling, redox conditions and volcanic activity). These data will be fed into an Earth Systems model for the Devonian carbon-cycle that we generate using inverse modelling techniques. The model will also incorporate data on the appearance of major plant groups and novelties (e.g. first forests).Together these data will shed light on the nature and timing of Devonian extinction events among primary producers and link them to changes in the carbon-cycle. Our research will clarify many aspects of the Devonian mass extinction (nature and timing) and link it to the monumental changes in carbon-cycling brought about by the dramatic evolution of terrestrial vegetation. This will also serve as a warning for the present day regarding consequences of human induced changes to the Earth's carbon-cycle bought about by deforestation, soil erosion and other detrimental activities.

复杂的多细胞生命大约在8亿年前首次出现在地球上，随后通过一个令人眼花缭乱的复杂的物种起源/灭绝模式而多样化。然而，这不是一个稳定和不间断的过程。至少有五次，地球上的生物群被一场灾难摧毁，这场灾难消灭了相当一部分生物多样性——包括整个生物群（高等分类群）。这些所谓的“大灭绝”从根本上改变了地球上生命的本质，使进化进入了一个完全不同的轨道。在“五大”物种大灭绝中，迄今为止最不为人所知的是发生在大约3.7亿年前的泥盆纪物种大灭绝。关于这一事件的时间和性质存在广泛的争论，这导致对其原因完全缺乏共识。该提案旨在从一个关注碳循环变化的新视角来研究泥盆纪大灭绝。目前，地球上有两个类似规模的碳循环：一个是基于光合作用的浮游生物的海洋碳循环，另一个是基于光合作用的陆地植物的陆地碳循环。泥盆纪期间，由于陆地植被的巨大变化，碳循环发生了根本性的变化。在泥盆纪开始时，陆地植物只有几厘米高，扎根于非常浅的土壤中，覆盖了大陆的有限区域。在泥盆纪末期，大片的大陆被几十米高的树木覆盖，这些树木深深扎根于成熟的土壤中。这些主要的植被变化引起了陆地碳循环的深刻变化（由于化学风化和生物质埋藏的碳封存）。我们假设是陆地碳循环的剧烈变化破坏了地球系统，导致了泥盆纪大灭绝。然而，我们认为这不是一个单一的灾难性事件（如导致白垩纪末期大灭绝的火石撞击），而是连续发生的，离散的形态/解剖创新导致了植物大小和覆盖范围的变化，从而导致了陆地碳循环的阶跃变化。该研究项目将集中于西班牙北部的泥盆纪序列。这些是理想的，因为它们：(i)非常完整，并且包含了已知的弗拉斯-法门纪和泥盆纪-石炭纪边界的灭绝事件；（二）在一个大的微大陆上孤立地积累，因此不受物种迁移/迁出和栖息地跟踪的影响；（iii）包含海洋浮游生物（栖生物和几丁质动物）和陆地植被（植物孢子/花粉）的优良化石记录。我们将通过物种起源/灭绝模式的研究来研究海洋浮游生物和陆地植被的进化动力学。这种生物多样性概况将与地球化学分析相结合，以确定地球碳循环中的扰动（除了营养循环、氧化还原条件和火山活动之外）。这些数据将被输入我们使用逆建模技术生成的泥盆纪碳循环地球系统模型。该模型还将纳入有关主要植物群和新物种（例如原始森林）外观的数据。这些数据将阐明泥盆纪主要生物灭绝事件的性质和时间，并将它们与碳循环的变化联系起来。我们的研究将阐明泥盆纪大灭绝的许多方面（性质和时间），并将其与陆地植被的剧烈进化所带来的碳循环的巨大变化联系起来。这也将对当今人类引起的地球碳循环变化的后果发出警告，这些变化是由森林砍伐、土壤侵蚀和其他有害活动引起的。

项目成果

Age of the basal 'Lower Old Red Sandstone' Stonehaven Group of Scotland: The oldest reported air-breathing land animal is Silurian (late Wenlock) in age

苏格兰斯通黑文群的基底“下老红砂岩”的年龄：报道的最古老的呼吸空气的陆地动物的年龄是志留纪（文洛克晚期）

• DOI: 10.1144/jgs2023-138
• 发表时间: 2023
• 期刊: Journal of the Geological Society
• 影响因子: 2.7
• 作者: Wellman C

Morphology and Wall Ultrastructure of the Devonian Spore Acinosporites macrospinosus Richardson 1965 and Its Bearing on the Origin of the Megaspore Apical Prominence

• DOI: 10.1086/720388
• 发表时间: 2022-04
• 期刊: International Journal of Plant Sciences
• 影响因子: 2.3
• 作者: C. Wellman

Terrestrialization in the Ordovician

奥陶纪陆地化

• DOI: 10.1144/sp532-2022-92
• 发表时间: 2022
• 期刊: Geological Society, London, Special Publications
• 作者: Wellman C

Dispersed spore assemblages from the Lower Devonian Rañeces - La Vid groups of Northern Spain: Palaeogeographical implications

西班牙北部下泥盆统 Rañeces - La Vid 群的分散孢子组合：古地理意义

• DOI: 10.1016/j.revpalbo.2022.104825
• 发表时间: 2023
• 期刊: Review of Palaeobotany and Palynology
• 影响因子: 1.9
• 作者: Wellman C

Middle Jurassic terrestrial environmental and floral changes linked to volcanism: Evidence from the Qinghai-Tibet Plateau, China

• DOI: 10.1016/j.gloplacha.2023.104094
• 发表时间: 2023-03
• 期刊: Global and Planetary Change
• 影响因子: 3.9
• 作者: Peixin Zhang;Minfang Yang;Jing Lu;Zhongfeng Jiang;Kai Zhou;Haoqing Liu;Zhen He;Ye Wang;X. Bian;L. Shao;J. Hilton;D. Bond