DISSERTATION RESEARCH: Quantification and Characterization of the Production of Methane in Living Trees

以前对活树中甲烷产生的研究表明，树木有可能成为全球重要的甲烷来源，甲烷是一种重要的温室气体。已知活树内部的木材腐烂是常见的，但从这种腐烂材料中产生的甲烷尚未被考虑在全球甲烷预算中。使用基于协作工具包的采样工作，将从西部针叶林的活树、枯木和碎片中收集气体，并在最大限度地增加碳储存从而限制甲烷产生的森林管理方法的背景下评估结果。森林及其在减轻全球变化对全世界数百万人健康的潜在灾难性影响方面的作用受到了极大关注。为了使森林管理在碳捕获方面尽可能有效，必须更好地了解森林与气候相互作用的基本动态。本项目将对高地森林的甲烷排放进行量化和定性，这可以使气候建模者和森林管理者了解树木甲烷排放在碳循环中的潜在作用。除了生成所需的数据，这项工作将资助研究生和本科生的研究经验。具体来说，这些资金将延长博士生的论文，并用于促进本科生的研究经验，与四年制大学的高等教育。在高地，硬木为主，美国东部森林，甲烷生产潜力的不同物种水平的模式的发生表明，最高的甲烷生产率驱动大量的通过树皮排放到大气中。初步通量估计表明，这一甲烷源的大小可能是在同一顺序的高地森林，土壤甲烷汇。这在多大程度上适用于更广泛的森林是未知的，在美国东部硬木森林树种的生理可能是特别有利于发展的实质性木材腐烂的活树。然而，针叶树种的生理学可以限制腐烂在活树中的传播，因此它们通过这种腐烂途径产生甲烷的潜力可能要低得多。基于用于测量东部硬木树甲烷产生的方法，研究人员将在美国西部针叶林进行配对的实地和实验室研究。具体而言，使用分布式，协作，基于套件的采样工作，气体将从西部针叶林的活树，枯木和碎片中收集。此外，将在一个时间序列上收集木材样本，并将其放置在静态室中，以评估甲烷通量的大小。将对这些碎片样本的一个子集进行微生物群落分析，以将观测到的甲烷通量率和内部甲烷浓度与活树和倒落枯木中的微生物动态联系起来。

Previous studies into the production of methane in living trees suggest that trees have the potential to be a globally significant source of methane, which is an important greenhouse gas. Wood-rot inside living trees is known to be common, but the production of methane from this rotting material has not been considered in global methane budgets. Using a collaborative kit-based sampling effort, gas will be collected from living trees, dead wood, and debris, in western conifer forests and results evaluated in the context of forest management approaches that maximize carbon storage and hence limit methane production. A great deal of attention has been focused on forests and their role in mitigating the potentially catastrophic impacts of global change on the health of millions of people worldwide. For forest management to be as effective as possible at carbon capture, it is imperative that a better understanding of the fundamental dynamics of forest-climate interactions is developed. The quantification and characterization of methane emission from upland forests that will be undertaken in this project can inform climate modelers and forest managers about the potential role of tree-methane emission in carbon cycling. Beyond generating needed data, the work will fund both graduate and undergraduate research experiences. Specifically, the funds will extend the dissertation of a 4th year doctoral student and be used to facilitate undergraduate research experiences with a four-year college of higher education.In upland, hardwood-dominated, eastern US forests, the occurrence of distinct species-level patterns in methane production potential suggests that the highest methane production rates drive substantial through-bark emission to the atmosphere. Initial flux estimates suggest that the magnitude of this methane source could be on the same order as the upland forest, soil methane sink. The extent to which this applies to forests more broadly is not known, as the physiology of tree species in eastern hardwood forests in the US may be particularly conducive to the development of substantive wood rot inside living trees. The physiology of coniferous species, however, can limit the spread of rot within living trees and so their potential to produce methane through this rot pathway could be much lower. Based on the methods used to measure methane production in eastern hardwood trees, the investigators will conduct paired field and laboratory studies in western US coniferous forests. Specifically, using a distributed, collaborative, kit-based sampling effort, gas will be collected from living trees, dead wood, and debris, in western conifer forests. In addition, wood samples will be collected across a chronosequence and placed in static chambers to assess the magnitude of methane flux. A subset of these debris samples will be subjected to microbial community analysis to relate observed methane flux rates and internal methane concentrations to microbial dynamics in living trees and downed dead wood.