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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”，它推动了土壤矿物质的风化和元素的生物地球化学循环，对地球大气二氧化碳历史产生了重大影响。如果正确的话，这一范式表明，泥盆纪（前 418-360 迈尔）森林生态系统的进化出现构成了显生宙整个 540 迈尔期间出现的地球化学碳循环的最重要的生物反馈。至关重要的是，树木的进化进步与其对古土壤的地球化学影响之间尚未建立联系。仍在等待一个因素影响另一个因素的直接证据，这主要是因为迄今为止缺乏跨学科调查。我们的提案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度腐烂森林的进化崛起如何加剧风化和成土作用的机制理解，而风化和成土作用构成了长期碳循环的主要生物反馈。我们的中心假设是，树木的进化进步使得古土壤中可以检测到地球化学效应，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，增加了表层土壤层同位素和元素富集的强度，增强了Ca-Si和Ca-P矿物的风化，以及成土粘土的形成，导致通过与释放的陆地Ca形成海洋碳酸盐来长期封存大气中的CO2。我们将通过获取和分析从北美东部地区的时间序列到代表地球向森林星球过渡的关键志留纪-泥盆纪区间的保存完好的古土壤剖面来研究这一研究假设。然后将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。这将首次允许混合和单一中泥盆纪森林的根结构与通过钻探复制未风化剖面获得的古土壤风化剖面直接相关。这些森林的风化将与“对照案例”进行比较，即来自志留纪和泥盆纪下游地区具有小型/浅根系统的前森林、早期维管束陆地植物的风化。这些地点为我们提供了以前未开发的能力，可以描述关键的志留纪-泥盆纪间隔期间植物-根系-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。应用针对当代土壤表面树木强烈集中的元素和同位素的地球化学分析，这些元素和同位素通过森林下的矿物风化而显示丰度的重大变化，为解决和重建森林生态系统演化不同阶段风化和成土作用的强度和深度提供了一种强有力的新策略。该项目紧紧围绕“提高当前对生命进化与地球之间相互作用的认识”，这代表了 NERC 地球系统科学主题中的三个高水平挑战之一。