Application of stable isotopes to terrestrial paleoclimate: tracing interactions among the soil-plant-atmosphere continuum

稳定同位素在陆地古气候中的应用：追踪土壤-植物-大气连续体之间的相互作用

• 批准号: 327706-2006
• 负责人: Webb, Elizabeth
• 金额: $ 1.4万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=362543
• 关键词: Application; stable; isotopes; terrestrial; paleoclimate

In order to understand the impact of human activity on the current trends in global climate change, we must first recognize the amplitude of natural climatic fluctuations throughout earth's recent history.  Scientists can use indirect measures of past climate to extend the relatively short historical climatic record.  The amounts of specific elements found in fossilized materials can provide information regarding the climatic conditions during their formation in the past.  Minerals, water and organic matter contain common elements, such as oxygen, carbon and iron that are composed of more than one stable isotope.  Isotopes are atoms of the same element that differ only in their mass, and commonly in their rate of chemical reaction.  The magnitude of the difference in reaction rates between two isotopes of the same element is sensitive to temperature and kinetic effects associated with biological functions such as photosynthesis, which are also sensitive to climate.  For example the ratio of heavy to light carbon-isotopes in plants is greater for warm-season grasses than trees that thrive in cooler climates.  It follows then that the carbon-isotope ratio of organic matter preserved in soils may be used to identify the presence of warm- versus cool-season vegetation growing on those soils in the past.  Likewise, minerals formed in plants as a by-product of solute-uptake, will have a higher ratio of heavier to light oxygen isotopes if grown in warm climates rather than cool climates.   My research program assesses the effects of climate and plant biology on the isotopic variations of natural materials cycled through the soil-plant-water system.  This study will focus on well-preserved plant residues in soils, such as minerals precipitated in the cells of grasses, cellulose, humic substances in soils and iron-rich minerals produced by plant decay.  Our goal is to develop and refine models that relate the isotopic composition of ancient plant materials to ancient continental climates.  In addition to paleoclimate applications, the stable isotopic analysis of biogenic materials preserved in soils provides a unique opportunity to learn about present and past biogeochemical cycles.

为了了解人类活动对当前全球气候变化趋势的影响，我们必须首先认识到地球近代史上自然气候波动的幅度。我们的科学家可以使用对过去气候的间接测量来延长相对较短的历史气候记录。在化石材料中发现的特定元素的数量可以提供关于它们过去形成过程中气候条件的信息。在矿物中，水和有机物包含共同的元素，如氧、碳和铁，这些元素由不止一个稳定同位素组成。同位素是相同元素的原子，只是质量不同。通常还取决于它们的化学反应速度。同一元素的两个同位素之间的反应速率差异的大小对温度和与生物功能(如光合作用)有关的动力学效应敏感，而光合作用也对气候敏感。例如，暖季草类植物中重碳同位素与轻碳同位素的比率大于在较冷气候中茁壮成长的树木。因此，土壤中保存的有机质的碳同位素比率可以用来识别过去在这些土壤上生长的暖季和冷季植被的存在。同样，植物中形成的矿物作为吸收溶质的副产品，如果生长在温暖的气候而不是寒冷的气候中，将具有更高的重氧同位素与轻氧同位素的比率。我的研究计划评估气候和植物生物学对土壤-植物-水系统中循环的天然物质同位素变化的影响。这项研究将集中在保存完好的土壤中的植物残留物，如在草类细胞中沉淀的矿物，纤维素，土壤中的腐殖质和植物腐烂产生的富铁矿物。我们的目标是开发和完善将古代植物材料的同位素组成与古代大陆气候联系起来的模型。除了古气候应用之外，保存在土壤中的生物物质的稳定同位素分析为了解现在和过去的生物地球化学循环提供了一个独特的机会。