LTREB: Collaborative Research: Long-term changes in peatland C fluxes and the interactive role of altered hydrology, vegetation, and redox supply in a changing climate

全球重要的碳（C）存储在北方（北方）泥炭地是脆弱的变化，改变降水和径流模式，地下水输入，并在高纬度地区的冻土（称为“永久冻土”，或“冰冻圈”）的范围内的变化。 这些变化会影响北方湿地的范围以及它们隔离和转化碳和其他营养物质的能力。2005年，阿拉斯加泥炭地实验（APEX）被创建，以研究土壤气候和植被变化对泥炭地碳循环的作用。在过去15年中，收集了关于土壤湿度和温度、植物组成和数量以及模拟洪水和干旱的地下水处理过程中排放的重要大气气体（如甲烷和二氧化碳）通量的核心数据。该小组先前调查的一个关键结果是，无论地下水位的位置如何，该实验地点的C排放量似乎都很高，这表明植物物种组成变化之间的相互作用对处理的反应强烈地控制了该生态系统保留C的能力。 这是环境生物学长期研究（LTREB）项目DEB-1354370的五年更新。该研究正在研究水文变化，植物物种组成和气候变化（特别是洪水和干旱）之间的相互作用，以控制碳存储在这泥炭地复杂;这项工作是必要的了解气候变化的影响，碳循环过程。 本科生、研究生和博士后研究人员都将接受实地和实验室技术方面的培训。研究结果还将纳入新的高中课程，用于培养科学夏令营。目前对泥炭地碳循环的看法是，大多数土壤碳矿化发生在相对较浅的通气泥炭层以上的水位（acrotelm），而较深的泥炭碳发生在缺氧层（catotelm）经历最小的分解。因此，地下水位的位置（以及相关的顶层厚度）被用作整体分解率和长期泥炭积累率的预测指标。然而，该团队在阿拉斯加沼泽（阿拉斯加泥炭地实验，APEX）中对地下水位位置进行了15年的操纵，结果挑战了这一观点，特别是表明饱和泥炭中的碳矿化比以前预期的要快，导致厌氧CO2产生的高通量。先前的分析表明，地下水位的位置对生态系统呼吸没有显着的影响，但它是可能的，这一结果是由于至少部分地发生在植被的变化，在较低（干燥）和较高（湿润）的地下水位位置。最初的实验设计不能解开的影响，植被水文泥炭氧化还原和碳通量的变化。因此，了解改变水文和植被对厌氧分解过程的相互作用，以及这如何管理泥炭地深层土壤碳库的周转，是LTREB第一阶段资金的主要目标。在最初的LTREB资助期间的结果表明，莎草和木贼（马尾）根际确实有泥炭和溶解有机物的氧化作用。然而，在这段时间的研究持续洪水提出了关键的差距，在这个系统中的微量气体生产控制的机械理解，并揭示了植物群落结构和藻类的优势可能有独特的控制土壤氧化还原过程和碳通量。洪水历史也产生了很强的控制藻类与异养微生物的相对活性，这取决于不同植物的碳底物的变化。确切地说，植物群落的变化如何与地下水位的变化相互作用，以控制电子供体和受体的供应，以及这如何控制低水位和高水位年份的厌氧代谢，是该合作团队在未来五年内将研究的关键问题。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进行评估，被认为值得支持审查标准。

Globally important carbon (C) stores in northern (boreal) peatlands are vulnerable to changes in altered precipitation and runoff patterns, groundwater inputs, and changes in the extent of frozen ground in high latitudes (called ‘permafrost’, or the ‘cryosphere’). These changes can affect the extent of boreal wetlands as well as their ability to sequester and transform C and other nutrients. In 2005, the Alaska Peatland Experiment (APEX) was created to examine the role of changing soil climate and vegetation on peatland C cycling. Over the past fifteen years, core data has been collected on soil moisture and temperature, plant composition and amount, and the fluxes of important atmospheric gases emitted (as methane and carbon dioxide) from water table treatments that simulate floods and droughts. A key result from this group's prior investigations was that C emissions from this experimental site appeared to be high, regardless of water table position, revealing that interactions among changes in plant species composition in response to the treatments were strongly controlling the ability of this ecosystem to retain C. This is a five-year renewal of a Long-Term Research in Environmental Biology (LTREB) project, DEB-1354370. The study is examining the interactions among changes in hydrology, plant species composition and changes in climate (particularly flooding and drought) in controlling C storage in this peatland complex; this work is necessary for understanding the consequences of an altered climate for C cycle processes. Undergraduates, graduate students and post-doctoral researchers will all be trained and in field and laboratory techniques. Results from the research will also be incorporated into new high school curricula for use in the Fostering Science summer camp.The current view of peatland carbon cycling is that the majority of soil carbon mineralization occurs in the relatively shallow aerated peat layer above the water table (acrotelm), and that deeper peat carbon occurring in anoxic layers (catotelm) undergoes minimal decomposition. As such, the position of the water table (and the associated thickness of the acrotelm) is used as a predictor of overall decomposition rates and long-term peat accumulation rates. However, findings from this team's fifteen-year manipulation of water table position in an Alaskan fen (Alaska Peatland Experiment, APEX) challenge this view, and in particular suggest that carbon mineralization in saturated peat is faster than previously expected, leading to high fluxes of anaerobic CO2 production. Prior analyses indicated no significant effect of water table position on ecosystem respiration, but it is possible that this result was due at least partially to changes in vegetation that have occurred both under lower (drier) and higher (wetter) water table positions. The initial experimental design could not disentangle the effects of changes in vegetation from hydrology on peat redox and C fluxes. As such, understanding the interactive effects of altered hydrology and vegetation on anaerobic decomposition processes, and how this governs the turnover of deep soil C pools in peatlands, was the prime objective of the first phase of LTREB funding. Results during that initial LTREB funding period showed that sedge and Equisetum (horsetail) rhizospheres indeed had oxidizing effects on peat and dissolved organic matter. However, persistent flooding over this period of research has presented key gaps in mechanistic understanding of controls on trace gas production in this system, and revealed that plant community structure and the dominance of algae likely have unique controls on soil redox processes and C fluxes. Flooding history also exerted strong control over the relative activity of algae vs. heterotrophic microorganisms, depending on changes in C substrates from different plants. Exactly how changes in plant community interact with altered water tables in governing the supply of electron donors and acceptors, and how this controls anaerobic metabolism in low- and high-water table years, are key questions this collaborative team will examine in the next five years.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.