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Doctoral Dissertation Research: Assessing Regeneration Niche Limitations to Upslope Migration of Subalpine Forests

博士论文研究：评估亚高山森林上坡迁移的再生生态位限制

基本信息

批准号：
1634163
负责人：
Thomas Veblen
金额：
$ 1.6万
依托单位：
University of Colorado at Boulder
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-09-01 至 2019-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634163&HistoricalAwards=false
关键词：
Doctoral Dissertation Research Assessing Regeneration

项目摘要

This doctoral dissertation research project will examine how tree regeneration in subalpine forests is being influenced by changes in climate and wildfire activity. By collecting and analyzing extensive field data on factors affecting tree seedling establishment and survival, the doctoral student will identify threats to subalpine forest resilience. The project will identify altered regeneration patterns in forests, thereby improving capabilities for forecasting broad-scale changes in subalpine forest sustainability and for understanding impacts on carbon storage and cycling, hydrologic processes, and ecosystem services. Because the study will be conducted in the kinds of forests that are widely distributed across the western United States, research results will have wide-ranging utility. By elucidating how the relatively fast pace of recent warming affects subalpine tree regeneration, this project will address societal needs for understanding and adapting to changes in forests and the ecosystem services they provide. Project findings will help land managers to develop appropriate plans for climate adaptation and to evaluate ecosystem vulnerability to climate changes. To communicate these research findings to land managers and other stakeholders, the investigators will host workshops that address how subalpine forests respond to changing temperatures regimes and increased disturbance by wildfire and bark beetles. The workshops also will facilitate discussions about adaptation strategies for likely forest changes expected under changing climatic and environmental conditions. The student and his advisor will develop curriculum materials and will lead field trips for K-12 education at underserved schools, and they will mentor undergraduate students as research assistants through established teaching and advising programs. As a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising student to establish a strong independent research career.Global distributions of tree species are closely related to climate conditions. As temperatures continue to increase, the suitable habitat for tree species is projected to shift upslope. To compensate for lost habitat at the lower elevation limit, subalpine tree species are expected to migrate upslope to maintain existing populations. To migrate upslope, trees must first produce sufficient seed, and seeds must arrive in suitable habitats for germination and survival. As part of this project, the doctoral student will measure these reproductive processes and link them to climatic and other environmental factors to build models assessing the feasibility of upslope migration of tree populations and the sustainability of existing subalpine forests. The project will address the following questions: (1) Will increasing fire frequency prevent tree populations from reaching the size and ages required for adequate seed production to maintain future forest cover? (2) As temperatures rise and moisture availability declines, is upslope migration of tree populations and the resilience of existing subalpine forests limited by seed production and lack of suitable habitats for seedling germination and survival? (3) How has the establishment of tree seedlings (over the last 80 years) been influenced by variability in climate? The student will use extensive field data collected from past disturbances and the natural topoclimatic variation across the ranges of subalpine tree species to mimic change in climatic conditions. He will quantify the long-term response of key regeneration processes like reproductive maturity, seed availability, and microsite limitations in response to climate variability and to changes in disturbance regimes. He then will link fine-scale field results to broad-scale spatial datasets to parameterize and implement a cross-scalar spatial model that will evaluate key limitations to seedling recruitment over a range of environmental change projections.

这一博士论文研究项目将研究气候变化和野火活动如何影响亚高山森林中的树木再生。通过收集和分析影响树苗建立和存活因素的大量现场数据，博士生将识别对亚高山森林弹性的威胁。该项目将确定森林中改变的更新模式，从而提高预测亚高山森林可持续性的大范围变化以及了解对碳储存和循环、水文过程和生态系统服务的影响的能力。因为这项研究将在美国西部广泛分布的森林中进行，所以研究结果将具有广泛的实用价值。通过阐明最近相对较快的变暖速度如何影响亚高山树木的再生，该项目将解决社会对了解和适应森林及其提供的生态系统服务变化的需求。项目结果将有助于土地管理者制定适当的气候适应计划，并评估生态系统对气候变化的脆弱性。为了将这些研究结果传达给土地管理者和其他利益攸关方，调查人员将主办研讨会，讨论亚高山森林如何应对不断变化的气温制度以及野火和树皮甲虫增加的干扰。讲习班还将促进关于气候和环境条件变化情况下可能发生的森林变化的适应战略的讨论。这名学生和他的导师将开发课程材料，并将在服务不足的学校领导K-12教育的实地考察，他们将通过既定的教学和咨询计划指导本科生作为研究助理。作为博士论文研究改进奖，该奖项将为有前途的学生建立强大的独立研究生涯提供支持。树种的全球分布与气候条件密切相关。随着气温的持续上升，适合树种生长的栖息地预计将向上移。为了弥补海拔较低时栖息地的损失，预计亚高山树种会向上迁移，以维持现有的种群。要向上迁移，树木必须首先产生足够的种子，种子必须到达适合发芽和生存的栖息地。作为该项目的一部分，博士生将测量这些繁殖过程，并将它们与气候和其他环境因素联系起来，以建立评估树木种群上坡迁移的可行性和现有亚高山森林的可持续性的模型。该项目将解决以下问题：(1)增加火灾频率是否会阻止树木种群达到维持未来森林覆盖所需的足够种子生产所需的大小和年龄？(2)随着气温上升和水分可获得性下降，树木种群的上坡迁移和现有亚高山森林的弹性是否受到种子生产和缺乏适合幼苗萌发和存活的栖息地的限制？(3)树苗的建立(在过去80年)如何受到气候变化的影响？学生将使用从过去的干扰中收集的大量野外数据和亚高山树种范围内的自然地形气候变化来模拟气候条件的变化。他将量化关键再生过程的长期反应，如生殖成熟度、种子可获得性和微站点限制，以应对气候变化和干扰制度的变化。然后，他将把精细的实地结果与大范围的空间数据集联系起来，以参数化和实施跨标量空间模型，该模型将根据一系列环境变化预测来评估苗木招募的关键限制。