CAREER: Mechanisms of Forest Nitrogen Retention Over Seasons, Sites, and Succession

职业：森林氮保留随季节、地点和演替的机制

• 批准号: 0845451
• 负责人: Christine Goodale
• 金额: $ 53.67万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0845451&HistoricalAwards=false
• 关键词: CAREER; Mechanisms; Forest; Nitrogen; Retention

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Current concepts of ecosystem ecology center on the coupling between nitrogen availability and biotic demand in controlling retention of nitrogen by ecosystems. Increased nitrogen loss is expected from ecosystems when the nutritional demands of plants are low, as in old age or during the dormant season, or when nitrogen availability has increased due to air pollution or fertilizer use. The proposed work confronts these models using three field experiments. In the first, nitrogen retention over the course of forest development in time will be examined through initiation of a long term experiment where nitrogen is added to abandoned agricultural fields of different ages in central New York. This will also enable testing the role of age and nitrogen deposition on forest carbon sequestration. The second derives from the observation that chronic nitrogen pollution has not led to the increases in stream water nitrate as expected. One constraint may be that the excess nitrogen is complexed by dissolved organic carbon produced during recovery that these ecosystems have undergone in recent years as acid rain was reduced. This will be tested by evaluating factors that control dissolved carbon and nitrate losses and by responses of both dissolved carbon and nitrate in experiments in New Hampshire where acidity is manipulated. The third will address the assumed role of plant uptake in controlling seasonal stream nitrate loss through a series of nitrogen additions to a watershed in central New York. This will also enable contrasts of the role of terrestrial versus aquatic nitrogen retention mechanisms and determination of the fate of nitrogen in soil organic matter. All three experiments seek to examine important intersections of forest carbon and nitrogen cycles, while employing new and existing field experiments, new data collections, and stable isotopes to develop a more complex understanding of the plant, soil, microbial and hydrologic factors that affect nitrogen retention. The global nitrogen cycle has been profoundly altered by human activities. Impacts of air pollution on downwind ecosystems depend on the fate of the added nitrogen. Uptake and retention by vegetation may stimulate carbon sequestration, at least for some forests, while losses of nitrate in stream water may acidify soils and surface waters and contribute to downstream eutrophication. Retention of nitrogen in relatively stable forms of soil organic matter could provide a long term sink for added nitrogen. This project will provide a more complete understanding of the effects of nitrogen on forest ecosystems and enable better management of affected forests. Activities as part of an integrated education and outreach program include collaboration with education specialists from the Paleontological Research Institution and Museum of the Earth in Ithaca, New York. This would include public outreach in connection with a visiting exhibit on forests, development of a K-12 teacher professional development workshop on forest ecosystems and impacts from air pollution, and development of a graduate student workshop on skills for partnering with science educators to produce useful education materials. This research would also establish a local watershed as a field site for teaching ecology to undergraduates. Together these partnerships will enable more effective science education and outreach to a much broader audience.

该奖项是根据2009年《美国恢复和再投资法案》(公法111-5)资助的。目前生态系统生态学的概念集中在控制生态系统对氮的保留方面氮的可获得性和生物需求之间的耦合。当植物的营养需求较低时，如在老年或休眠季节，或者当由于空气污染或化肥使用而增加了氮素可获得性时，生态系统的氮素损失预计会增加。所提出的工作使用了三个现场实验来面对这些模型。首先，将通过启动一项长期实验，将氮素添加到纽约中部不同年龄的废弃农田中，来检验森林发展过程中的氮素保留量。这也将使测试年龄和氮沉积对森林碳汇的作用成为可能。第二个原因是观察到，慢性氮污染并没有像预期的那样导致溪水硝酸盐的增加。一个制约因素可能是，过量的氮被近年来随着酸雨减少而在恢复过程中产生的溶解有机碳所复杂化。这一点将通过评估控制溶解碳和硝酸盐损失的因素以及在酸度被操纵的新罕布夏州的实验中通过溶解碳和硝酸盐的反应来检验。第三项研究将探讨植物吸收在控制季节性溪流硝酸盐流失中所扮演的角色，通过向纽约市中心的一个分水岭添加一系列氮素。这也将能够对比陆地和水生氮保持机制的作用，并确定氮在土壤有机质中的去向。所有这三个实验都试图研究森林碳和氮循环的重要交叉点，同时利用新的和现有的田间实验、新的数据收集和稳定同位素来发展对影响氮保持的植物、土壤、微生物和水文因素的更复杂的理解。全球氮循环已经被人类活动深刻地改变了。空气污染对顺风生态系统的影响取决于添加的氮的命运。至少对某些森林来说，植被的吸收和保留可能会刺激碳的固存，而溪水中硝酸盐的损失可能会使土壤和地表水酸化，并导致下游的富营养化。以相对稳定的土壤有机质形式保留氮素可以为增加的氮素提供一个长期的汇。该项目将使人们更全面地了解氮素对森林生态系统的影响，并能够更好地管理受影响的森林。作为综合教育和推广计划的一部分，活动包括与纽约伊萨卡古生物研究所和地球博物馆的教育专家合作。这将包括与森林参观展览有关的公众宣传，举办关于森林生态系统和空气污染影响的K-12教师专业发展讲习班，以及举办关于与科学教育工作者合作编写有用教材的技能的研究生讲习班。这项研究还将建立一个当地的分水岭，作为向本科生教授生态学的实地场地。这些伙伴关系将使科学教育更加有效，并扩大到更广泛的受众。