RAPID: Resprouting and resilience: The role of nonstructural carbon reserves in fostering the longevity of coast redwood

海岸红杉是地球上最大的生物之一。几代人以来，这一标志性物种一直受到公众的珍视，并被视为保护的旗舰。有趣的是，红杉可以在容易发生火灾的生态系统中存活数千年。红杉的重新发芽能力，或者激活树皮下休眠的芽，长出新的茎、枝和叶，是一种适应能力，可以提高火灾后的存活率。就像人类储存脂肪作为能量储备一样，树木储存糖和淀粉作为储备，为再生提供所需的碳和能量。该项目将使用碳定年法来估计这些碳水化合物的储存时间。在其他物种中，在100岁的树木中发现了10岁的保留区，但在古老的红杉中，保留区可能要古老得多。研究将在加利福尼亚州圣克鲁斯附近的大盆地红杉州立公园进行，那里的树木高达2500年，高100米（330英尺）。2020年8月19日，CZU闪电复合火灾烧毁了公园，提供了一个独特的机会来观察非常大的老树的再生。该项目将向公众传达红杉树迷人的科学，对他们来说，红杉树具有普遍的吸引力。具体活动将包括与北亚利桑那大学媒体专家合作编写的广播和录像故事，以及一次面对面的外联活动。野火在加州很常见，火灾年表表明，许多海岸红杉（Sequoia sempervirens）树林每10-25年经历一次火灾。然而，2020年发生的火灾的规模和严重程度是前所未有的。该项目解决的主要问题是，“用于支持火灾受损红木再生的非结构碳[NSC]储备有多老？”一个先前开发的概念模型假设树木活力与储存的NSC储备的大小和周转时间之间的联系。该模型预测，最高的、占主导地位的、最健壮的树木将拥有大量的年轻NSC储备（最近的光合作用，在过去一年内从大气中移除），而不那么健壮的树木将拥有更少和更老的NSC储备。长寿命树木的NSC储备有多老还不得而知。该项目将收集大盆地红杉州立公园大火损坏的树木的外生芽和茎木芯，并通过在北亚利桑那大学的新型MICADAS（迷你碳测年系统）AMS（加速器质谱仪）上测量其14C特征来确定这些样品中NSC的年龄（从大气中移除的时间）。该项目将是第一个在红木中调查NSC的项目，也是第一个使用14C方法来估计用于支持红木再生的NSC储备的年龄的项目。这项工作有可能改变人们对这种独特而长寿物种的生物学认识。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。

Coast redwood trees are among the largest living organisms on Earth. For generations, this iconic species has been treasured by the public and served as a flagship for conservation. Intriguingly, redwoods can live for thousands of years in ecosystems that are prone to fire. The redwood’s ability to resprout, or activate dormant buds beneath the bark and grow new stems, branches, and leaves, is an adaptation that enhances survival following fire. Just as humans store fat as an energy reserve, trees store sugars and starch as reserves that provide the carbon and energy needed for resprouting. This project will use carbon dating methods to estimate how long these carbohydrates have been held in reserve. In other species, decade-old reserves have been identified in 100-year-old trees, but in ancient redwoods the reserves could be much older. Research will be conducted at Big Basin Redwoods State Park, near Santa Cruz, CA, where trees are up to 2500 years old and 100 meters (330 ft) tall. On August 19, 2020, the CZU Lightning Complex Fire burned through the Park, presenting a unique opportunity to look at resprouting in very large, old trees. The project will communicate the fascinating science of redwood trees to the public, to whom these trees have universal appeal. Specific activities will include radio and video stories developed in collaboration with Northern Arizona University media specialists and an in-person outreach event.Wildfire is a common occurrence in California, and fire chronologies indicate that many coast redwood (Sequoia sempervirens) groves experience fire every 10-25 years. However, fires of the size and severity that occurred during 2020 are unprecedented. The principal question this project addresses is, “How old are the nonstructural carbon [NSC] reserves used to support resprouting in fire-damaged redwood?” A previously-developed conceptual model hypothesizes links between tree vigor and the size and turnover time of stored NSC reserves. This model predicts that the tallest, dominant, and most vigorous trees will have large reserves of young NSC (recent photosynthate, removed from the atmosphere within the last year), whereas less vigorous trees will have smaller and older NSC reserves. How old NSC reserves are in long-lived trees is unknown. This project will collect epicormic sprouts and stem wood cores from fire-damaged trees in Big Basin Redwoods State Park, and determine the age of NSC in those samples (time since removal from the atmosphere) by measuring its 14C signature on the new MICADAS (Mini Carbon Dating System) AMS (Accelerator Mass Spectrometer) at Northern Arizona University. This project will be the first to investigate NSC in redwood and the first to use 14C methods to estimate the age of NSC reserves that are being drawn on to support redwood resprouting. This work has the potential to transform understanding of the biology of this unique and long-lived species.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.