Collaborative Research: Effects of Elevated CO2 on Forest N Cycling: Assessment with Large-Scale 15N Tracers and Modeling

合作研究：二氧化碳浓度升高对森林氮循环的影响：使用大规模 15N 示踪剂和建模进行评估

• 批准号: 0236356
• 负责人: Adrien Finzi
• 金额: $ 30万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0236356&HistoricalAwards=false
• 关键词: Collaborative; Research; Effects; Elevated; CO2

Abstract. Forest ecosystems exchange large amounts of carbon (C) with the atmosphere each year, an exchange that is strongly constrained by nutrient cycling. Forest productivity is anticipated to increase with the projected doubling in the concentration of atmospheric CO2 over the next century. A critical area for research and synthesis concerns the feedback effects of elevated CO2 on soil N cycling. Elevated CO2 significantly increased plant productivity, the uptake of N from soils and the flux of C to soil microbes but did not change litter chemistry, decomposition, the mass balance of N among ecosystem pools, gross and net N mineralization or plant N availability. Even though plant N availability did not increase under elevated CO2, there is no indication that N is progressively limiting the enhanced productivity of this ecosystem now in it sixth growing season under elevated CO2. This result is surprising given that (i) Net Primary Productivity is demonstrably N limited in this ecosystem, (ii) that there is intense competition for available Namong plants, microbes and abiotic sinks in soils, and (iii) that the long-term productivity of asingle prototype FACE plot at this research site was stimulated by elevated CO2 only after the addition of N fertilizer. These results suggest a fundamental gap in our understanding of the coupled nature of C and N cycles in forest ecosystems, and an opportunity to expand our knowledge of ecosystem biogeochemistry. This research will have direct benefits to society by addressing a major potential limitation to C sequestration in ecosystems that cover over 24 million hectares of forest land in the southeastern US; ecosystems that are likely to be managed for their C-sink potential under the Kyoto Protocol.Broader Impacts: Given the interdisciplinary and multi-institutional nature of the Duke Forest FACE experiment, this research will have impacts that extend well beyond this collaborative team. This grant will train future scientists and recruit and retain women graduate students, and will make an effort to broaden the participation of minorities by actively participating in the SEEDS program (a joint program of ESA and UNCF). This project will enhance infrastructure for research by contributing data sets and an enhanced model to current synthesis activities at NCEAS and an international network of 15 N tracer study sites. We expect the impact of this work to continue to be high, both in advances to fundamental ecosystem science, and in the demonstrable application of ecosystem science to issues of global change; issues that will increasingly impact society over the next century.

抽象的。 森林生态系统每年与大气交换大量碳（C），这种交换受到养分循环的强烈限制。预计下个世纪大气二氧化碳浓度将增加一倍，森林生产力预计将提高。研究和合成的一个关键领域涉及二氧化碳浓度升高对土壤氮循环的反馈效应。 升高的二氧化碳显着增加了植物生产力、土壤中氮的吸收以及土壤微生物的碳通量，但没有改变凋落物化学、分解、生态系统库中氮的质量平衡、总氮矿化和净氮矿化或植物氮可用性。尽管在二氧化碳浓度升高的情况下植物氮的利用率没有增加，但没有迹象表明氮正在逐渐限制该生态系统生产力的提高，目前正处于二氧化碳浓度升高的第六个生长季节。这一结果令人惊讶，因为（i）该生态系统中的净初级生产力明显受到氮的限制，（ii）对土壤中可用的纳蒙植物、微生物和非生物汇存在激烈的竞争，以及（iii）长期生产力仅在添加氮肥后，该研究地点的单个原型 FACE 地块才受到二氧化碳浓度升高的刺激。这些结果表明我们对森林生态系统中碳和氮循环耦合性质的理解存在根本差距，并且是扩展我们对生态系统生物地球化学知识的机会。这项研究将通过解决覆盖美国东南部超过 2400 万公顷林地的生态系统中碳封存的主要潜在限制，为社会带来直接利益；更广泛的影响：鉴于杜克森林 FACE 实验的跨学科和多机构性质，这项研究的影响将远远超出该合作团队的范围。这笔赠款将培训未来的科学家并招募和留住女研究生，并将通过积极参与 SEEDS 计划（欧空局和 UNCF 的联合计划）来努力扩大少数族裔的参与。 该项目将通过向 NCEAS 和 15 个 N 示踪剂研究站点的国际网络当前的合成活动提供数据集和增强模型来增强研究基础设施。我们预计这项工作将继续产生巨大的影响，无论是在基础生态系统科学的进步方面，还是在生态系统科学对全球变化问题的明显应用方面；这些问题将在下个世纪对社会产生越来越大的影响。