LTREB: Testing Paradigms About Plant Functional Responses to Environmental Change

需要长期的生态实验来模拟未来的条件，这样科学家就可以研究它们对生态群落的潜在影响。这项研究使用了一项长达20年的野外实验，名为BioCON，该实验将草原植物群落上方大气中的二氧化碳浓度提高到预计将在本世纪晚些时候出现的水平。该实验旨在研究大气中较高的二氧化碳水平如何影响不同种类植物的生长。该实验还旨在了解土壤氮（植物生长所需的重要营养物质）的可用性如何影响植物在光合作用过程中吸收更高水平二氧化碳的能力。这项研究的数据将通过雪松溪长期生态研究网站公开。每年有超过2500名K-12学生和教师参观BioCON，其中包括美国原住民学生的教师。每年夏天，大学生们都在BioCON工作并学习如何开展自己的研究项目。新的K-12课程计划以及以可持续发展科学为主题的YouTube频道MinuteEarth的视频将专门介绍从BioCON获得的新知识。通过持续测量官能团和官能团混合物对二氧化碳（CO2）和氮处理的反应，本研究将检验两种假设。第一组使用功能性状分类框架来预测对eCO2和N的直接功能群响应（即，在没有土壤介导的反馈、物种相互作用或与气候随机或定向变化的相互作用的情况下预期的响应）。第二组假设长期结果将偏离基于预期直接反应的预测，因为修改过程涉及生理适应，对地上和地下资源供应和土壤pH的功能群效应，以及处理与气候变化之间的相互作用。BioCON中长寿命的多年生植物对CO2和N的响应尚未达到平衡，表现出与气候年复一年变化的相互作用，并产生土壤介导的反馈。在BioCON中，经过20年的研究，C4物种在高CO2条件下的生产力越来越高，而C3物种的CO2效益逐渐消失，这与目前的理论相矛盾。了解这些不同的反应以及它们是否会继续是这项研究的主要重点，同时了解功能群在全球环境变化下与生态系统相关的其他长期过程中的作用，包括生产力、分解、养分循环和水通量。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Long-term ecological experiments are needed that simulate the conditions of the future so that scientists can study their potential impacts on ecological communities. This study uses a 20-year old, field experiment, called BioCON, that raises the carbon dioxide concentrations in the atmosphere above prairie plant communities to levels that are expected to occur later in this century. The experiment is designed to study how higher carbon dioxide levels in the atmosphere affects the growth of different kinds of plants. The experiment is also designed to understand how the availability of soil nitrogen, an important nutrient that plants need to grow, influences the ability of plants to take up higher levels of carbon dioxide during photosynthesis. Data from the study will be made publicly available through the Cedar Creek, Long Term Ecological Research website. BioCON is visited by over 2500 K-12 students and teachers annually, including teachers of Native American students. College students work and learn how to carry out their own research projects in BioCON each summer. New K-12 lesson plans as well as videos for the sustainability science themed YouTube Channel MinuteEarth will be developed that specifically feature new knowledge gained from BioCON. Through continued measurements of functional group and functional group mixture responses to carbon dioxide (CO2) and nitrogen treatments, this study will test two kinds of hypotheses. The first set uses a functional trait classification framework to develop predictions regarding direct functional group responses to eCO2 and N (i.e., responses expected in the absence of soil-mediated feedbacks, species interactions, or interactions with stochastic or directional changes in climate). The second set posits that long-term outcomes will diverge from predictions based on expected direct responses because of modifying processes, involving physiological acclimation, functional group effects on aboveground and belowground resource supply and soil pH, and interactions between treatments and variation in climate. The long-lived perennials in BioCON have not yet equilibrated in their response to CO2 and N, exhibiting interactions with year-to-year variation in climate and generating soil-mediated feedbacks. In BioCON, across 20 years, C4 species have become increasingly productive under high CO2 whereas the benefit of CO2 has gradually disappeared for C3 species, contradicting current theory. Understanding these divergent responses and whether they will continue is a major focus of the study, along with understanding the role of functional groups with respect to other long-term processes relevant to ecosystems under global environmental change, including productivity, decomposition, nutrient cycling, and water fluxes.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.