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Evolutionary rise of deep-rooting forests and enhanced chemical weathering: Quantitative investigations into the current paradigm

深根森林的进化崛起和化学风化的增强：对当前范式的定量研究

基本信息

批准号：
NE/J007897/1
负责人：
Christopher Berry
金额：
$ 16.07万
依托单位：
CARDIFF UNIVERSITY
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ007897%2F1
关键词：
Evolutionary rise deep rooting forests

项目摘要

The co-evolution and geographical spread of trees and deep-rooting systems is widely proposed to represent the 'Devonian engine' of global change that drove the weathering of soil minerals and biogeochemical cycling of elements to exert a major influence on the Earth's atmospheric CO2 history. If correct, this paradigm suggests the evolutionary appearance of forested ecosystems through the Devonian (418-360 Myr ago) constitutes the single most important biotic feedback on the geochemical carbon cycle to emerge during the entire 540 Myr duration of the Phanaerozoic. Crucially, no link has yet been established between the evolutionary advance of trees and their geochemical impacts on palaeosols. Direct evidence that one has affected the other is still awaited, largely because of the lack of cross-disciplinary investigations to date.Our proposal addresses this high level 'earth system science' challenge. The overarching objective is to provide a mechanistic understanding of how the evolutionary rise of deep-rotting forests intensified weathering and pedogenesis that constitute the primary biotic feedbacks on the long-term C-cycle. Our central hypothesis is that the evolutionary advance of trees left geochemical effects detectable in palaeosols as forested ecosystems increased the quantity and depth of chemical energy transported into the soil through roots, mycorrhizal fungi and litter. This intensified soil acidification, increased the strength of isotopic and elemental enrichment in surface soil horizons, enhanced the weathering of Ca-Si and Ca-P minerals, and the formation of pedogenic clays, leading to long-term sequestration of atmospheric CO2 through the formation of marine carbonates with the liberated terrestrial Ca. We will investigate this research hypothesis by obtaining and analysing well-preserved palaeosol profiles from a time sequence of localities in the eastern North America through the critical Silurian-Devonian interval that represents Earth's transition to a forested planet. These palaeosol sequences will then be subjected to targeted geochemical, clay mineralogical and palaeontological analyses. This will allow, for the first time, the rooting structures of mixed and monospecific Mid-Devonian forests to be directly linked to palaeosol weathering profiles obtained by drilling replicate unweathered profiles. Weathering by these forests will be compared with the 'control case' - weathering by pre-forest, early vascular land plants with diminutive/shallow rooting systems from Silurian and lower Devonian localities. These sites afford us the previously unexploited ability to characterize the evolution of plant-root-soil relationships during the critical Silurian-Devonian interval, whilst at the same time controlling for the effects of palaeogeography and provenance on palaeosol development. Applying geochemical analyses targeted at elements and isotopes that are strongly concentrated by trees at the surface of contemporary soils, and which show major changes in abundance through mineral weathering under forests, provides a powerful new strategy to resolve and reconstruct the intensity and depth of weathering and pedogenesis at different stages in the evolution of forested ecosystems. The project is tightly focused on "improving current knowledge of the interaction between the evolution of life and the Earth", which represents one of the three high level challenges within NERC's Earth System Science Theme.

树木和深根系统的共同进化和地理分布被广泛认为代表了全球变化的“泥盆纪引擎”，该引擎推动了土壤矿物的风化和元素的生物地球化学循环，对地球大气二氧化碳的历史产生了重大影响。如果正确，这一范式表明，整个泥盆纪(418-360Myr前)森林生态系统的进化外观构成了在显生目整个540 Myr期间出现的关于地球化学碳循环的唯一最重要的生物反馈。至关重要的是，树木的进化进展与它们对古土壤的地球化学影响之间还没有建立起任何联系。其中一个影响另一个的直接证据仍在等待，这主要是因为到目前为止还缺乏跨学科的调查。我们的建议解决了这一高水平的地球系统科学挑战。总体目标是提供对深腐烂森林的进化崛起如何加剧风化和土壤作用的机械理解，这些作用构成了对长期C周期的主要生物反馈。我们的中心假设是，树木的进化在古土壤中留下了可检测到的地球化学效应，因为森林生态系统增加了通过根、菌根真菌和凋落物输送到土壤中的化学能的数量和深度。这加剧了土壤酸化，增加了表层土壤中同位素和元素的富集度，促进了Ca-Si和Ca-P矿物的风化和成壤粘土的形成，通过与释放的陆地Ca形成海相碳酸盐，导致大气CO2的长期封存。我们将通过获取和分析北美东部地区经过志留纪-泥盆纪关键时期的保存完好的古土壤剖面来研究这一研究假设，这一时期代表着地球向森林行星的过渡。然后对这些古土壤序列进行有针对性的地球化学、粘土矿物学和古生物学分析。这将首次使中泥盆世混交林和单一种森林的根部结构与通过钻探获得的古土壤风化剖面直接联系起来，复制未风化剖面。这些森林的风化将与‘对照案例’相比较--由森林前的早期维管陆地植物风化，这些植物具有来自志留系和下泥盆纪地区的小型/浅根系统。这些遗址为我们提供了以前未被开发的能力，以表征关键志留纪-泥盆纪时期植物-根-土壤关系的演变，同时控制古地理和物源对古土壤发育的影响。针对当代土壤表面树木强烈集中的元素和同位素进行地球化学分析，显示出森林下矿物风化导致丰度的重大变化，为解决和重建森林生态系统演化不同阶段的风化和成壤作用的强度和深度提供了一种强有力的新战略。该项目的重点是“改善生命进化与地球相互作用的现有知识”，这是NERC地球系统科学主题中的三个高级别挑战之一。