DISSERTATION RESEARCH: Carbon Cycle Changes in a Changing Climate: Using 13C and 14C to Partition Ecosystem Respiration in Tundra Undergoing Permafrost Thaw

论文研究：气候变化中的碳循环变化：利用 13C 和 14C 来划分永久冻土解冻苔原中的生态系统呼吸

• 批准号: 1011284
• 负责人: Edward Schuur
• 金额: $ 1.49万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1011284&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Carbon; Cycle; Changes

Permafrost soils, which are soils frozen for two or more consecutive years, store vast quantities of carbon (C). These soils are reservoirs of C because thousands of years of cold temperatures have prevented the microbial decomposition of soil organic carbon (SOC), and thus the subsequent release of carbon dioxide (CO2) from soils to the atmosphere. However, permafrost soils are very vulnerable to warming; as the climate warms, permafrost soils begin to thaw, which allows microbes to access and decompose stored SOC , thereby releasing CO2. Permafrost thaw, therefore, has the potential to become a positive feedback to climate change: CO2 in the atmosphere can increase warming, and warming of permafrost soils can result in more CO2 release to the atmosphere via increased rates of decomposition and ecosystem respiration. However, permafrost thaw can also increase plant growth, which takes CO2 out of the atmosphere via photosynthesis, and may, in the short term, result in a negative feedback to climate change. Thus the relative responses of both soil microbes and plants to permafrost thaw determine whether, on balance, permafrost ecosystems add CO2 to the atmosphere (microbial response and positive feedback) or whether the ecosystem takes CO2 from the atmosphere (plant response and negative feedback.) The main objective of this research is to quantify the response of four components of ecosystem respiration, all of which result in release of CO2 to the atmosphere (aboveground plant structures, belowground plant structures, surface soil microbes, and deep soil microbes) to permafrost thaw in order to determine whether plant or microbial responses are dominating the Alaska tundra's changing carbon cycle. Natural abundances of two carbon isotopes, 13C and 14C, will be used to identify the sources of respired CO2. By measuring the isotopic values of CO2 sources as well as ecosystem respiration, the relative contribution of soil microbes and plants to carbon fluxes can be calculated. This ecosystem respiration partitioning will be performed seasonally in a natural gradient of permafrost thaw, in a tundra warming experiment, and in an area with two different amounts of vegetation and two different soil climates to explore the effects of permafrost thaw on the carbon balance of tundra ecosystems.Throughout the course of this research, undergraduate students will be trained, 8th grade students will be educated, and a layperson's guide to C cycling in permafrost will be created. Finally, the results of this study will be important to climate models; these models do not currently consider biological responses to the physics of climate warming.

永久冻土是指连续两年或以上冻结的土壤，储存了大量的碳 (C)。这些土壤是碳库，因为数千年的低温阻止了土壤有机碳（SOC）的微生物分解，从而阻止了二氧化碳（CO2）随后从土壤释放到大气中。 然而，永久冻土很容易受到变暖的影响。随着气候变暖，永久冻土开始融化，微生物可以进入并分解储存的 SOC，从而释放二氧化碳。 因此，永久冻土融化有可能成为对气候变化的正反馈：大气中的二氧化碳会加剧变暖，而永久冻土的变暖会通过增加分解速度和生态系统呼吸，导致更多的二氧化碳释放到大气中。然而，永久冻土融化也会促进植物生长，通过光合作用将二氧化碳从大气中吸收出来，并可能在短期内对气候变化产生负反馈。因此，土壤微生物和植物对永久冻土融化的相对反应决定了永久冻土生态系统是否向大气中添加二氧化碳（微生物反应和正反馈），或者生态系统是否从大气中吸收二氧化碳（植物反应和负反馈）。这项研究的主要目的是量化生态系统呼吸的四个组成部分的响应，所有这些组成部分都会向大气中释放二氧化碳（地上植物结构、地下植物结构、表层土壤微生物、和深层土壤微生物）到永久冻土融化，以确定植物或微生物反应是否主导阿拉斯加苔原不断变化的碳循环。 两种碳同位素 13C 和 14C 的自然丰度将用于确定呼吸二氧化碳的来源。 通过测量二氧化碳源的同位素值以及生态系统呼吸，可以计算土壤微生物和植物对碳通量的相对贡献。 这种生态系统呼吸分区将在永久冻土融化的自然梯度、苔原变暖实验以及具有两种不同植被数量和两种不同土壤气候的区域中按季节进行，以探索永久冻土融化对苔原碳平衡的影响在整个研究过程中，将对本科生进行培训，对八年级学生进行教育，并将创建一份关于永久冻土中 C 循环的外行指南。 最后，这项研究的结果对气候模型很重要；这些模型目前没有考虑生物对气候变暖的物理反应。