Collaborative Research: Climate controls over ecosystem respiration: Using isotopes to determine the sources and age of respired carbon

合作研究：气候对生态系统呼吸的控制：利用同位素确定呼吸碳的来源和年龄

• 批准号: 0223193
• 负责人: Edward Schuur
• 金额: $ 13.87万
• 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: 2002
• 资助国家: 美国
• 起止时间: 2002-10-01 至 2006-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0223193&HistoricalAwards=false
• 关键词: Collaborative; Research; Climate; controls; over

ABSTRACTCarbon enters ecosystems through a single process, photosynthesis, and nearly all is returned to the atmosphere through respiration, some 50-80% of which occurs below ground. Soil respiration integrates root metabolism and the activity of decomposer organisms. While the major processes affecting plant metabolic (autotrophic) respiration and decomposition rates (heterotrophic respiration) are known, the ability to predict variations in soil respiration in space and time is limited - a major uncertainty in the current and future carbon cycle. The work proposed here will combine new measurement and modeling approaches for separating autotrophic and heterotrophic respiration, and determining the age of C respired from soils. At field sites in the Ameriflux network that span a range of North American biomes and climates, these methods will include: (1) frequent, automated, measurements of soil respiration and related factors; (2) isotope mass balance methods based on measurements of stable isotopes and radiocarbon in respired CO2; and (3) incubations to determine responses of heterotrophic respiration components to changing soil conditions; and (4) at some sites, manipulation of soil moisture content through rainfall exclusion. The data generated will be used to partition soil respired C into autotrophic and heterotrophic components, to determine the age of heterotrophically respired C and identify the components of soil organic matter contributing to its production, and to determine how these relationships chance with controlling variables(photosynthesis rate, soil conditions, etc). The results will be used to parameterize a newautotrophic respiration component of the CASA ecosystem model, and to test how well the model predicts the balance of sources of heterotrophic respiration on seasonal to interannual timescales. Predictions of the CASA model will be further tested across regional gradients spanning (1) a climosequence and (2) a suite of sites from tropical forest to tundra. We will use atmospheric records of seasonal variation in C isotopes (13C at the global network sites and 14C in atmospheric CO2 at Point Barrow, Alaska) as a global test of the CASA model's ability to determine the seasonal to interannual exchange of C between northern hemisphere terrestrial ecosystems and the atmosphere.Intellectual merit. Separating the components of ecosystem respiration is one of the fundamentally important research challenges in ecosystem science. This activity will use new tools, in particular, innovative use of the radiocarbon tracer in measurements and models, to develop process level understanding of C fluxes at selected Ameriflux sites.Broader impacts. This work will advance fundamental understanding of how terrestrial ecosystems influence the global carbon cycle, and will improve projections of future atmospheric concentrations of carbon dioxide by showing how heterotrophic respiration will respond to changes in temperature and moisture. Our program to educate students through a short course in radiocarbon at the W.M. Keck Carbon Cycle Accelerator Mass Spectrometry facility will train the next generation of scientists in the applications of radiocarbon to study land and ocean C cycling.

摘要碳通过光合作用这一单一过程进入生态系统，几乎所有碳都通过呼吸作用返回大气，其中约50-80%发生在地下。土壤呼吸结合了根代谢和分解生物的活动。虽然影响植物代谢（自养）呼吸和分解速率（异养呼吸）的主要过程是已知的，但预测土壤呼吸在空间和时间上的变化的能力是有限的，这是当前和未来碳循环的主要不确定性。本文提出的工作将结合新的测量和建模方法来分离自养和异养呼吸，并确定从土壤中呼吸的C的年龄。在北美生物群落和气候范围内的Ameriflux网络的现场站点，这些方法将包括：(1)频繁、自动化地测量土壤呼吸和相关因素；(2)基于呼吸CO2中稳定同位素和放射性碳测量的同位素质量平衡方法；(3)培养测定异养呼吸组分对土壤条件变化的响应；(4)在一些站点，通过降雨排除来控制土壤含水量。生成的数据将用于将土壤呼吸C划分为自养和异养组分，确定异养呼吸C的年龄，确定对其产生有贡献的土壤有机质组分，并确定这些关系如何与控制变量（光合速率，土壤条件等）发生变化。这些结果将用于参数化CASA生态系统模型中一个新的自养呼吸成分，并测试该模型在季节到年际时间尺度上预测异养呼吸源平衡的效果。CASA模型的预测将进一步在区域梯度上进行测试，包括(1)气候序列和(2)从热带森林到苔原的一系列地点。我们将使用C同位素季节变化的大气记录（全球网络站点的13C和阿拉斯加州巴罗点的大气CO2中的14C）作为CASA模式确定北半球陆地生态系统与大气之间季节至年际C交换能力的全球测试。知识价值。分离生态系统呼吸的组分是生态系统科学研究的重要课题之一。这项活动将使用新工具，特别是在测量和模型中创新性地使用放射性碳示踪剂，以便在选定的美洲通量场址发展对碳通量的过程级理解。更广泛的影响。这项工作将促进对陆地生态系统如何影响全球碳循环的基本理解，并将通过展示异养呼吸如何响应温度和湿度的变化来改善对未来大气二氧化碳浓度的预测。我们在W.M.凯克碳循环加速器质谱设施通过放射性碳短期课程教育学生的项目，将培训下一代科学家应用放射性碳来研究陆地和海洋碳循环。