Collaborative Research: Are Amazon forest trees source or sink limited? Mapping hydraulic traits to carbon allocation strategies to decipher forest function during drought

了解大片热带森林将如何应对气候变化，包括干旱频率的增加，这一点很重要，因为这些森林在地球的碳循环中发挥着重要作用。该奖项提供资金，研究亚马逊森林将如何应对干旱，如最近的厄尔尼诺现象。研究人员将研究单个物种如何捕获和利用碳和水，并利用这些数据来了解物种的生物多样性如何使整个森林更能抵御干旱。研究结果将被整合到模型中，并预测森林物种组成的差异如何导致整个森林对干旱反应的差异。该奖项将评估生物群落的组成如何影响其整体功能以及未来变化对整个热带森林的影响。该项目将促进国际合作和美国本科生在巴西进行研究的培训。通过生物圈二号的外展计划和科学节，将提高公众对这些问题的认识，科学节每年向100多名中学生介绍亚马逊地区的情况。植物干旱响应科学在很大程度上假设环境调节光合作用碳源（“C源调节”），然后根据固定的异速生长规则将其分配给生长和其他功能。然而，有一种新的观点认为，植物内C-汇过程（生长，储存和呼吸）直接受环境和植物内反馈（'C-汇调节'假说），这样的分配和汇过程的变化是干旱响应的一个关键机制。现实地传播这种机制的生态系统规模需要会计的物种特异性的策略，不同的植物经济谱。为了现实地检验这一假设，下面的挑战将是我通过整合测量树C源（光合作用）和C-汇（生长、储存、呼吸）过程，以确定调节机制;通过关注资源和植物水力特性的分布，将干旱响应机制提升到生态系统水平，绘制植物经济谱;观测生态系统尺度的光合碳源（Gross Ecosystem Productivity，GEP）和蒸腾耗水量。本文对树木碳源和碳汇过程的控制进行了评价，包括Kok效应，非结构碳储存，和植物与水的关系该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.

Understanding how large expanses of tropical forests will respond to climate variation, including increasing frequency of droughts, is important since these forests play a big role in the planet's carbon cycle. This award provides funds to study how the Amazon forest will respond to droughts such as experienced in the recent El Nino. Researchers will examine how individual species capture and use carbon and water, and use that data to understand how biodiversity of species makes the whole forest more resilient to droughts. The results will be integrated to model and predict how differences in forest species composition result in differences in whole-forest responses to drought. This award will evaluate how composition of biological communities influences their overall function and the effects of future changes on entire tropical forests. The project will advance international collaboration and the training of U.S. undergraduates to do research in Brazil. Increased public awareness of these issues will occur through outreach programs at the Biosphere 2, and a Science Festival which facilitates targeted presentations about the Amazon to 100+ middle-high school students/year. The science of plant drought response has largely assumed that environment regulates photosynthetic source of carbon ('C-source regulation'), which is then allocated to growth and other functions according to fixed allometric rules. There is an emerging view, however, that within-plant C-sink processes (growth, storage, and respiration) are directly regulated by the environment and by within-plant feedbacks (the 'C-sink regulation' hypothesis), such that changes in allocation and sink processes are a key mechanism of drought response. Realistically propagating such mechanisms to the ecosystem scale requires accounting for species-specific strategies that vary across the plant economic spectrum. To realistically test this hypothesis, the following challenges will be me through integrating measurements of tree C-source (photosynthesis) and C-sink (growth, storage, respiration) processes across a range of hydraulic traits to identify regulating mechanisms; Upscaling the mechanisms of drought response to the ecosystem level by focusing on distributions of both resources and plant hydraulic traits mapped to the plant economic spectrum; and Observing the ecosystem-scale photosynthetic C source (Gross Ecosystem Productivity, GEP) and water loss by transpiration. This evaluation of the controls on tree C-source and C-sink processes - including the Kok effect, Non-Structural C storage, and plant water relations - will transform our understanding of Amazon forest C dynamics and assessment of the forest's future under climate change.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.