Doctoral Dissertation Research: Mapping and Modeling Shrub Expansion in the Arctic National Wildlife Refuge

博士论文研究：北极国家野生动物保护区灌木扩张的测绘和建模

• 批准号: 1203444
• 负责人: David Cairns
• 金额: $ 1.2万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1203444&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Mapping; Modeling

Shrub expansion is a global phenomenon involving the transition from herbaceous to woody cover. This phenomenon is one of the most recognized components of terrestrial changes in the Arctic, but its precise characteristics in the latter half of the 20th century are largely unknown. This doctoral dissertation research project seeks to quantify the historic spatial characteristics of shrub expansion in the northern Alaska and investigate how landscape-scale environmental characteristics (topography, hydrology, shrub reproductive characteristics, and the existence, strength, and directionality of associated feedbacks) influence its development. The doctoral student's first objective will be accomplished by using historical (1950s-1980s) aerial imagery available from the United States Geological Survey (USGS) and high-resolution satellite imagery from the late 2000s. These imagery sets facilitate the mapping of shrub patches and their expansion over this time period. Pattern metric analysis then will be applied to these maps to determine how characteristics like patch density, patch size variability, and distance between patches have changed. The second objective will be accomplished through the development of a simple computer model that simulates shrub expansion over time in response to manipulations of shrub reproductive characteristics, topography and hydrology, and the existence, strength, and directionality of associated feedbacks. Statistical comparisons of the model output and maps of observed patterns of expansion will facilitate the generation of hypotheses regarding the landscape-level environmental controls on expansion. Because of variability in the cartographic scale of the USGS images, underestimations of shrub cover are likely. In order to assure its utility, the computer model to be refined will require fine-scale data regarding changes in shrub patches available from the U.S. Fish and Wildlife Service and the National Park Service. These new imagery sets will provide the detail needed for validation of the computer model.This research project will provide an improved understanding of the changing characteristics of shrub expansion in northern Alaska as well as a stronger foundation for the generation of hypotheses regarding its landscape-scale environmental controls. This will allow for future research avenues, such as field-based observations and/or experiments to test these hypotheses and the incorporation of nutrient-cycling characteristics (a dominant fine-scale environmental control on shrub expansion) into the simulation model. The project will provide an excellent education and training opportunity for an undergraduate student, and it will include a set of outreach efforts, including research presentations to students and members of the public in communities of primarily Alaskan Natives, such as Atqasuk, Barrow, Kaktovik, and Anaktuvuk Pass. Because shrub expansion is a process that affects the environment of native communities, the research should help communities address historic patterns and mechanisms. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

灌木扩张是一种全球现象，涉及从草本到木本覆盖的过渡。 这一现象是北极陆地变化中最受认可的组成部分之一，但其在世纪后半叶的确切特征在很大程度上是未知的。 本博士论文研究项目旨在量化的历史空间特征的灌木扩张在北方阿拉斯加和调查如何规模的环境特征（地形，水文，灌木繁殖特性，以及相关反馈的存在，强度和方向性）影响其发展。 博士生的第一个目标将通过使用美国地质调查局（USGS）提供的历史（1950 - 1980年代）航空图像和2000年代后期的高分辨率卫星图像来实现。 这些图像集有助于绘制灌木斑块及其在这段时间内的扩展。 然后将对这些地图应用模式度量分析，以确定斑块密度、斑块大小变异性和斑块之间的距离等特征如何变化。 第二个目标将通过开发一个简单的计算机模型来实现，该模型模拟灌木随着时间的推移而扩大，以应对灌木繁殖特性，地形和水文，以及相关反馈的存在，强度和方向性的操纵。 模型输出和观察到的扩张模式的地图的统计比较，将有助于生成关于扩张的环境控制的假设。 由于美国地质勘探局图像的制图比例的可变性，灌木覆盖的低估是可能的。 为了确保其实用性，有待完善的计算机模型将需要美国鱼类和野生动物管理局和国家公园管理局提供的有关灌木斑块变化的精细数据。 这些新的图像集将提供所需的计算机model.This研究项目的验证细节将提供一个更好的理解灌木扩张在北方阿拉斯加的变化特征，以及一个更强大的基础上产生的假设，其规模的环境控制。 这将允许未来的研究途径，如基于实地的观察和/或实验，以测试这些假设和营养循环特性（占主导地位的小规模环境控制灌木扩张）纳入模拟模型。 该项目将为本科生提供一个极好的教育和培训机会，它将包括一系列的推广工作，包括向主要是阿拉斯加原住民社区的学生和公众成员进行研究报告，如Atqasuk，巴罗，Kaktovik和Anaktuvuk Pass。 由于灌木扩张是一个影响当地社区环境的过程，因此这项研究应该帮助社区解决历史模式和机制。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。