Dissertation Research: The Role of Anthropogenic Acidification in Stream Nitrogen Cycling: Understanding Stress Effects on Ecosystem Function

论文研究：人为酸化在河流氮循环中的作用：了解压力对生态系统功能的影响

• 批准号: 0808361
• 负责人: Herbert Valett
• 金额: $ 1.18万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0808361&HistoricalAwards=false
• 关键词: Dissertation; Research; Role; Anthropogenic; Acidification

This research will investigate how stream acidification caused by acid rain influences the biological removal of nitrogen from surface waters. Understanding environmental controls on nitrogen uptake is essential as human activities continue to increase stream concentrations of nitrogen pollutants. While stream acidification is known to have negative effects on fish and invertebrate communities, there is little understanding of acid effects on nitrogen cycling. The investigators will study nine streams in Shenandoah National Park, VA, that differ in chronic pH to infer how nitrogen uptake processes change with acidification over time.The researchers use a basic concept of stress response - a shift in resource allocation away from growth and towards maintenance - to guide investigations at both organismal and ecosystem scales. Laboratory experiments are designed to measure biomass-specific rates of nitrogen uptake, respiration, and enzyme activity by leaf biofilms from all streams. Isotopic techniques will be used to measure the nitrogen demand of streams in situ, and these rates will be combined with whole-stream rates of respiration and microbial biomass in an effort to interpret ecosystem behavior in the physiological context of stress response. Finally, the investigators will use isotopic techniques in four streams along the pH gradient to measure nitrogen demand under experimentally-increased levels of nitrogen concentration to predict future stream uptake potential.

这项研究将调查酸雨引起的溪流酸化如何影响地表水中氮的生物去除。随着人类活动不断增加氮污染物的河流浓度，了解环境对氮吸收的控制至关重要。虽然已知溪流酸化对鱼类和无脊椎动物群落有负面影响，但对酸化对氮循环的影响知之甚少。研究人员将研究弗吉尼亚州谢南多国家公园的九条溪流，它们的慢性PH值不同，以推断氮素吸收过程如何随着时间的推移而随酸化而变化。研究人员使用应激反应的基本概念--资源分配从生长转向维护--来指导生物和生态系统规模的研究。实验室实验旨在测量来自所有溪流的叶片生物膜对氮素的吸收、呼吸和酶活性的特定生物量速率。将使用同位素技术来现场测量溪流的氮素需求，并将这些速率与整个溪流的呼吸速率和微生物生物量结合起来，努力解释在胁迫反应的生理背景下的生态系统行为。最后，研究人员将在沿pH梯度的四条溪流中使用同位素技术来测量在实验增加的氮浓度水平下的氮需求，以预测未来溪流的吸收潜力。