International Research Fellowship Program: Does the Foliar Nitrogen Isoptope Variability in Rain Forest Trees Reflect Niche Partitioning, Biophysical Processes or Climate?

国际研究奖学金计划：雨林树木叶面氮同位素变异是否反映了生态位划分、生物物理过程或气候？

• 批准号: 1012703
• 负责人: Jordan Mayor
• 金额: $ 18.41万
• 依托单位: Mayor Jordan R
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2012-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1012703&HistoricalAwards=false
• 关键词: International; Research; Fellowship; Program; Does

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a 24-month research fellowship by Dr. Jordan Mayor to work with Dr. Benjamin Turner at the Smithsonian Tropical Research Institute in Panama. The availability of nitrogen (N) to plants is a primary control over forest productivity and ecosystem dynamics throughout much of the world. Tropical forests are presumed to be relatively N-rich yet their growth and adaptations respond to natural and anthropogenic changes in N-cycling and climate. Due to the complexity of the N cycle and the various types of plant responses to N limitations, there is a strong research need to use the ratio of heavy to light stable isotope measurements of N to integrate both biogeochemical processes and plant community responses to fluctuations in N availability. However, to be confident in the use and interpretation of foliar N isotope ratios, underlying mechanistic processes must be better understood. The PI, while housed within the Soils Biogeochemistry laboratory of Dr. Benjamin Turner, will meet the above research need by measuring stable isotope ratios from all three forms of plant available soil N, along with tree root and leaf tissue, across three experimental systems throughout Panamanian rainforest. The experimental systems were selected to target the main hypothesized controls over plant N isotope values: precipitation, soil nutrient bioavailability, and the type of root-associated mycorrhizal fungi. Each of the three experimental systems is designed to target specific hypotheses and, when combined, provide for a unified theory on the causes of variability in tree N isotope patterns in tropical forests. Human activities can increase N availability in ecosystems either by increasing N inputs through fertilizer addition or atmospheric deposition, or by speeding up internal recycling of N as a result of altered climate or landscape degradation. This joint research will inform the interpretation of relatively simple foliar analyses so that complex, time-integrated differences in N-cycles can be better understood and changes to them easily detected. In a time of rapid global change, these natural indexes will undoubtedly prove useful to forest monitoring efforts. In addition to the benefits of differentiating the underlying causes of tree N isotope ratios globally, these data will also permit testing for tree specialization on specific forms of soil N - a hypothesized mechanism for permitting the coexistence, rather than competitive exclusion, of otherwise similar tree species in biodiverse rainforest.

国际研究奖学金项目使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Jordan Mayor博士与Benjamin Turner博士在巴拿马史密森尼热带研究所开展为期24个月的研究。在世界大部分地区，植物对氮的可利用性是控制森林生产力和生态系统动态的主要因素。热带森林被认为是相对富氮的，但它们的生长和适应对n循环和气候的自然和人为变化作出反应。由于氮循环的复杂性和不同类型植物对氮限制的响应，迫切需要利用重、轻稳定同位素测量氮的比值来整合生物地球化学过程和植物群落对氮有效性波动的响应。然而，为了对叶面N同位素比值的使用和解释有信心，必须更好地了解潜在的机制过程。该项目位于本杰明·特纳博士的土壤生物地球化学实验室内，将通过在巴拿马雨林的三个实验系统中测量所有三种形式的植物有效土壤氮的稳定同位素比率，以及树根和叶片组织，来满足上述研究需求。实验系统的选择是针对植物N同位素值的主要假设控制因素：降水、土壤养分生物有效性和根相关菌根真菌的类型。这三个实验系统中的每一个都是针对特定的假设设计的，当结合起来时，就提供了关于热带森林树木N同位素模式变异原因的统一理论。人类活动可以通过施肥或大气沉降增加N输入，或通过气候变化或景观退化加速N的内部循环，从而增加生态系统中的N可利用性。这项联合研究将为相对简单的叶面分析提供解释，以便更好地理解n循环中复杂的时间积分差异，并容易检测到它们的变化。在全球迅速变化的时代，这些自然指数无疑将证明对森林监测工作是有用的。除了在全球范围内区分树木N同位素比率的潜在原因的好处之外，这些数据还将允许对特定形式土壤N的树木专一性进行测试-这是一种在生物多样性雨林中允许其他相似树种共存而不是竞争排斥的假设机制。