Doctoral Dissertation Research: High-Elevation Deciduous Forest Structure: A Test of the Slow-Seedling Hypothesis

这项博士论文研究将探讨苗木环境、树冠结构、气候变化、干扰类型和历史等因素对高山森林落叶阔叶树种相对于针叶针叶树种优势度的相对贡献和相互作用。传统的理解认为，高山森林以针叶针叶树为主，但在一些地区，存在阔叶高山森林。威廉·邦德提出的“慢苗”假说认为，落叶阔叶树是更好的竞争者，这主要是因为它们对光照和土壤水分等资源的局部变化有更强的适应性，而针叶针叶树对低温和土壤酸度等逆境因素更耐受。该项目将增加有关物种如何应对沿海拔梯度的环境条件变化的知识，特别是在生命的不同阶段。该项目将通过加强对敏感高海拔森林的森林构成和结构的控制的基本知识，帮助增进对地理和生物科学的了解。更具体地说，该项目将提高对高山森林环境中树木再生的了解，特别是当它们受到气候或其他环境条件变化的影响时。该项目还将提供关于高山环境中落叶阔叶树种或针叶针叶树种相对优势的变化将如何影响辐射吸收、碳循环的季节性、积雪融化以及森林对火灾或虫害干扰的敏感性的新见解。该项目的数据将通过一套数据库提供给其他学者。该项目将为两名本科生提供特殊教育和培训机会，并将开发一个教育模块，并在中学课堂上进行测试。作为博士论文研究改进奖，该奖项还将为有前途的学生建立强大的独立研究生涯提供支持。博士研究生的论文研究将得到该奖项的支持，他们将研究对苗木建立至关重要的特定生态相关因素，包括光、海拔、冠层覆盖、土壤养分和景观曲率。她将测量海拔梯度上不同森林类型之间的结构特性差异，并将使用树木年轮方法检查树木对每种森林类型的气候和干扰历史的反应。这项研究将与经验丰富的日本生态学家高桥光一合作，在日本中部相谷国家公园的日本阿尔卑斯山山坡上的八个森林地点进行。虽然是在日本进行的，但研究结果将有助于更好地了解全国各地的森林动态，包括美国的高山森林。

This doctoral dissertation research will investigate the relative contributions and interactions of seedling environment, canopy structure, climate variation, and the type and history of disturbance as factors contributing to dominance of deciduous broad-leaved species as opposed to needle-leaved conifers in alpine forests. Conventional understanding has held that alpine forests are dominated by needle-leaved conifers, but at some locales, broad-leaf alpine forests exist. A "slow-seedling" hypothesis articulated by William Bond posits that deciduous broad-leaved seedlings are superior competitors, largely because of their greater adaptability to localized changes in the availability of resources like light and soil moisture, while needle-leaved conifers are more tolerant to stressors like low temperatures and soil acidity. This project will increase knowledge regarding how species respond to variability in environmental conditions along an elevation gradient, especially at different stages of life. The project will help advance understanding in the geographic and biological sciences by improving basic knowledge of the controls on forest composition and structure of sensitive high-elevation forests. More specifically, the project will improve understanding of tree regeneration in alpine forest environments, especially when they are subjected to changes in climate or other environmental conditions. The project also will provide new insights regarding the ways in which shifts in the relative dominance of either deciduous broad-leaved species or needle-leaved conifers in the alpine environment would affect radiation absorption, the seasonality of carbon cycling, snow melt, and the susceptibility of forests to disturbance from fire or insect outbreaks. Data from this project will become available to other scholars through a set of databases. The project will provide special education and training opportunities for two undergraduate students, and an educational module will be developed and tested in middle-school classes. 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.The doctoral student whose dissertation research will be supported by this award will examine the specific ecological correlates important for seedling establishment, including light, elevation, canopy cover, soil nutrients, and landscape curvature. She will measure how structural properties differ between forest types across the elevation gradient, and she will examine the response of trees to climatic and disturbances histories in each forest type using tree-ring methods. The research will be conducted at eight sites in the forests on the slopes of the Japanese Alps in Chubu-Sangaku National Park in central Japan in collaboration with an experienced Japanese ecologist, Koichi Takahashi. Although conducted in Japan, the research findings will have utility to better understand forest dynamics around the nation, including in alpine forests of the U.S.