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: 2006
• 资助国家: 加拿大
• 起止时间: 2006-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=332954
• 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全球气候变化当前趋势的影响，我们必须首先认识到整个地球近期历史的自然文化波动的放大器。科学家可以使用过去气候的间接度量来扩展相对短暂的历史文化记录。化石材料中发现的特定元素的数量可以提供有关其过去形成过程中文化条件的信息。矿物质，水和有机物包含由多个稳定同位素组成的氧，碳和铁等共同元素。同位素是与仅在质量上不同的相同元素的原子，通常在化学反应速率上。同一元素的两个同位素之间的反应速率差异对与生物学功能（如光合作用）相关的温度和动力学作用敏感，这些效应也对气候敏感。例如，与在凉爽的气候中繁衍生息的树木相比，温暖季节的草中植物中重碳和同位体的比率更大。因此，保存在土壤中的有机物的碳 - 异位比率可用于确定过去在这些土壤上生长的温暖季节与凉爽的植被的存在。同样，如果在温暖的气候中生长而不是凉爽的攀爬，则在植物中形成的矿物质作为固体摄取的副产品将具有更高的重量与轻度氧同位素。我的研究计划评估了气候和植物生物学对通过土壤植物 - 水系统循环的天然材料的同位素变化的影响。这项研究将集中于保存完好的植物保留在土壤中的植物，例如保存在草的细胞中，纤维素，土壤中的腐殖质和由植物衰变产生的富含铁的矿物质中的矿物质。我们的目标是开发和完善将古代植物材料与古代连续登山者相关的模型。除了古气候应用外，保存在土壤中的生物材料的稳定同位素分析为了解当前和过去的生物地球化学周期提供了独特的机会。