Doctoral Dissertation Research: Understanding and Managing Ecosystem Change at the Forest-Peatland Ecotone

这一博士论文改进项目将调查环境条件变化对温带和其他非北方地区森林损失和随后的泥炭地扩张的模式和机制的影响。这位博士生将使用各种方法重建并比较过去一个世纪和过去一千年发生的火-气候-植被动力学。该项目的结果将揭示曾经是森林但现在是泥炭堆积的地点是否是新的生态系统，或者这些地区过去是否发生过这种转变，可能是由于干旱条件和火灾频率与今天观察到的相似。土地管理者对这些结果很感兴趣，他们需要工具来确定如何最好地管理改变后的生态系统。通过确定是否(以及哪些)生态阈值已被越过，该项目将为有关土地管理最佳做法的决策提供至关重要的投入。这位博士生将与区域土地管理者和其他利益相关者密切合作，包括土地所有者和教育工作者，以确保项目成果可用于为合作土地使用决策提供参考。PIS还将让K-12和大学生参与现场实践工作，从而为未来的科学家在调查环境变化的原因和后果时使用多种证据做好准备。此外，作为博士论文研究改进奖，该奖项将提供支持，使有前途的研究生能够建立强大的独立研究生涯。这个博士论文改进项目的总体目标是为森林生态系统火制度变化导致的替代稳定状态的科学文献做出贡献。运用古生态学、树枝生态学和群落生态学的方法，本研究将在不同的时空尺度上研究火对泥炭-森林交错带生态系统结构的影响。泥炭-森林交错带是一个过渡地带，与林线一样，对火和气候的变化特别敏感。该项目涉及以下问题：(1)气候条件不同的后欧洲定居时期的火灾活动与定居前条件下的火灾活动在数量上有何不同？(2)在最近的极端温暖/干燥和寒冷/潮湿时期，火灾对森林-泥炭地交错带的植被群落有何影响？(3)什么机制有利于一个地点从森林覆盖的土地过渡到泥炭堆积的土地？具体地说，博士生将使用树轮火灾伤痕日期、林分结构重建和沉积记录来回答这些问题。此外，将结合非生物和生物因素的调查，对对照和焚烧地点的现今植被组成/结构进行调查，以揭示泥炭堆积状态持续存在的机制。虽然这个项目将集中在巴塔哥尼亚西南部的森林-泥炭地交错带，但这项研究将为处理许多其他地区，包括美国的一些地区的环境变化的互动影响提供新的见解和方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This doctoral dissertation improvement project will investigate the impacts of changing environmental conditions on the patterns and mechanisms of forest loss and subsequent peatland expansion in temperate and other non-boreal regions. Using a variety of methods, the doctoral student will reconstruct and compare fire-climate-vegetation dynamics of the past century to those that have occurred over the past millennium. The results of this project will reveal whether once-forested but now peat-accumulating sites are novel ecosystems, or whether such transitions have occurred in the past in these regions, possible due to drought conditions and fire frequencies that are similar to those observed today. These results are of interest to land managers, who require tools to determine how best to manage altered ecosystems. By identifying whether (and which) ecological thresholds have been crossed, this project will provide crucial input for decision-making regarding best practices for land management. The doctoral student will work closely with regional land managers and other stakeholders, including land owners and educators, to ensure that project results are available to inform collaborative land use decisions. The PIs will also engage K-12 and college students in hands-on fieldwork, thus preparing future scientists to employ multiple lines of evidence in investigating the causes and consequences of environmental change. In addition, as a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising graduate student to establish a strong independent research career.The overarching objective of this doctoral dissertation improvement project is to contribute to the scientific literature on alternative stable states that result from changes in the fire regimes of forested ecosystems. Using methods from paleoecology, dendroecology, and community ecology, this research will examine fire-mediated effects on ecosystem structure at varying spatiotemporal scales at the peatland-forest ecotone, a transition zone that, like tree line, is particularly sensitive to changes in fire and climate. The project addresses the following questions: (1) How has fire activity during post-European settlement periods with distinct climate conditions differed quantitatively from that of pre-settlement conditions? (2) How has fire impacted the vegetation community of the forest-peatland ecotone during the most recent extreme warm/dry and cool/wet periods? (3) What are the mechanisms that favor a transition from forested to peat-accumulating lands in a site? Specifically, the doctoral student will use tree-ring fire scar dates, forest stand structure reconstructions, and sedimentary records to answer these questions. In addition, surveys of present-day vegetation composition/structure at control and burned sites will be paired with those of abiotic and biotic factors to uncover the mechanisms underlying the persistence of the peat-accumulating state. Although this project will focus on the forest-peatland ecotone of southwestern Patagonia, the research will provide new insights and approaches for dealing with the interactive effects of environmental change in many other regions, including some in the United States.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.