LTREB: Quantifying the recovery of central Appalachian forests during the final chapter of society's inadvertent nitrogen fertilization experiment.

自工业革命开始以来，化石燃料的燃烧导致了美国东部森林的氮污染。这在社会上造成了一个无意的实验，产生了两个相反的后果。森林只保留了一小部分增加的氮。其余的被冲到下游，降低了水质。氮污染还作为一种肥料，增强了树木和土壤储存碳的能力，减缓了气候变化。然而，由于《清洁空气法》的成功实施，氮污染有所下降，这些后果是否会持续下去仍不得而知。值得注意的是，在社会无意实验的最后阶段，缺乏可用于调查美国东部森林如何从氮污染中恢复的长期记录。该研究通过西弗吉尼亚州Fernow实验森林对氮污染反应的长期记录，探讨了这些后果是否会持续、恢复或达到新的常态。该项目通过实地考察和课堂活动，吸引西弗吉尼亚州塔克县当地八年级学生参与科学。这项研究将全国最长的溪流数据集之一与Fernow实验森林中最长的流域氮添加实验之一的停止结合起来。据推测，氮的减少会引发生态系统的恢复，其中树木将向地下的根和共生真菌输送更多的碳以获取氮，最终导致生态系统氮损失和碳储存的减少。通过跟踪四个环境氮污染下降的流域的恢复情况，以及一个在2020年停止氮肥施肥的实验流域，对这一假设进行了验证。在这些流域中，通过树木和微生物物种组成的新测量以及树木在根系和共生真菌中的碳投资评估，维持和加强了溪流氮和森林碳储量的长期记录，以揭示生态系统响应的机制。这项研究改进了生态系统模型中的过程，以提高我们对森林恢复到氮污染下降的预测性理解。该项目由生态系统科学和促进竞争研究的既定计划（EPSCoR）共同资助。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。

Since the start of the industrial revolution, the burning of fossil fuels has led to nitrogen pollution of Eastern US forests. This created an inadvertent experiment by society that had two opposing consequences. Forests retained only a fraction of this added nitrogen. The rest washed downstream and reduced water quality. Nitrogen pollution also acted as a fertilizer which enhanced the ability of trees and soils to store carbon and slow climate change. However, it remains unknown whether these consequences will persist as nitrogen pollution declines due to the success of the Clean Air Act. Notably, there is a lack of long-term records that can be used to investigate how Eastern US forests recover from nitrogen pollution during the final chapter of society’s inadvertent experiment. The research addresses whether these consequences will persist, recover, or reach a new normal, through long-term records of forest responses to nitrogen pollution at the Fernow Experimental Forest in West Virginia. The project broadens participation in science by engaging local 8th grade students in rural Tucker County, WV through field trips and in-class activities. This research couples one of the country’s longest stream water datasets with the cessation of one of its longest watershed nitrogen addition experiments at the Fernow Experimental Forest. Reductions in nitrogen are hypothesized to trigger ecosystem recovery, wherein trees will send more carbon below ground to roots and symbiotic fungi for nitrogen acquisition ultimately leading to reductions in ecosystem nitrogen losses and carbon storage. This hypothesis was tested by tracking the recovery of four watersheds experiencing declines in ambient nitrogen pollution as well as in an experimental watershed where nitrogen fertilization ceased in 2020. Across these watersheds, long-term records of stream water nitrogen and forest carbon storage are maintained and enhanced by new measurements of tree and microbial species composition as well as assessments of carbon investment by trees in roots and symbiotic fungi to reveal the mechanisms of ecosystem responses. The research refines and informs processes in an ecosystem model to improve our predictive understanding of forest recovery to declines in nitrogen pollution.This project is jointly funded by Ecosystem Science and the Established Program to Stimulate Competitive Research (EPSCoR).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.