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

本博士论文研究将调查幼苗环境、冠层结构、气候变化以及干扰的类型和历史的相对贡献和相互作用，作为高山森林中落叶阔叶树种相对于针叶树种的优势因素。 传统认识认为，高山森林以针叶林为主，但在某些地区也存在阔叶高山林。 威廉·邦德提出的“慢苗”假说认为，落叶阔叶树苗是更优秀的竞争者，这主要是因为它们对光照和土壤湿度等资源的局部变化具有更强的适应性，而针叶针叶树对低温和土壤酸度等压力源更能耐受。 该项目将增加有关物种如何响应海拔梯度上的环境条件变化的知识，特别是在生命的不同阶段。 该项目将通过提高对敏感高海拔森林的森林组成和结构控制的基础知识，帮助增进对地理和生物科学的理解。 更具体地说，该项目将增进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。 该项目还将提供新的见解，了解高山环境中落叶阔叶树种或针叶树种的相对优势的变化将如何影响辐射吸收、碳循环的季节性、融雪以及森林对火灾或昆虫爆发干扰的敏感性。 该项目的数据将通过一组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班级进行测试。 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。获得该奖项支持的论文研究的博士生将研究对幼苗生长重要的特定生态相关因素，包括光照、海拔、冠层覆盖、土壤养分和景观曲率。 她将测量不同森林类型在海拔梯度上结构特性的差异，并使用树木年轮方法检查每种森林类型中树木对气候和干扰历史的响应。 该研究将与经验丰富的日本生态学家 Koichi Takahashi 合作，在日本中部中部山岳国家公园日本阿尔卑斯山斜坡森林中的八个地点进行。 尽管在日本进行，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.