Doctoral Dissertation Research: Climate-Induced Range Dynamics in Eastern U.S. Forests

物种分布的结构和动态的许多生态学模型都基于这样的假设，即物种在其地理范围的中心最丰富，而在范围边缘最少。此外，人们通常认为，在牧场边缘，物种更有压力，更容易受到环境变化的影响。这些假设被广泛接受，但基于的经验证据很少。目前寻求预测物种范围变化以应对气候变化的模型假定，处于其范围边缘的物种主要受到气候的限制。这一博士论文研究改进项目将通过评估几个主要树种在中心和边缘附近的树木生长、气候、干扰和物种相互作用之间的关系，来测试这一假设对生长在阿巴拉契亚山脉南部的树木的有效性。每年分解的树木生态数据将用于全面分析几十年到几个世纪的树木生长反应和森林-林分动态的空间和时间变异性。这项研究的总体目标是评估气候和干扰过程对阿巴拉契亚栎松林的组成、结构和动态的影响，并确定这些影响是否与地理范围内的位置有关。从阿巴拉契亚山脉中南部的国家森林、国家公园和私人森林保护区的地点收集的森林调查和树木年轮数据将用于比较几个物种范围中心和边缘附近的树木建立、生长和死亡模式。这些比较将提供有关限制这些树种的地理分布的因素以及树种的范围可能如何随气候和干扰而变化的信息。分析气候和干扰对这些地点植被动态的相对重要性将增加对物种分布限制的基本了解，并为旨在预测和缓解树种对气候变化的反应的保护工作提供信息。气候变化造成的物种分布的戏剧性变化已经被记录在案，并预计将继续应对快速的全球变暖。气候变化对生态系统健康构成了许多威胁，包括生物多样性的丧失、外来物种的传播和物种的灭绝。缓解这些威胁需要了解影响物种范围结构和动态的机制。该项目将提供关于限制阿巴拉契亚树种在其南部山脉边界附近地理分布的因素的信息，并能够对物种范围动态进行更准确的预测。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研究生涯。

Many ecological models of the structure and dynamics of species distributions are based on the assumption that species are most abundant at the center of their geographic range and least abundant at range margins. Moreover, it is often assumed that species are more stressed and vulnerable to environmental change at range margins. These assumptions are widely accepted but are based on very little empirical evidence. Current models that seek to project shifts in species ranges in response to climate change assume that species at their range margins are limited primarily by climate. This Doctoral Dissertation Research Improvement project will test the validity of this assumption for trees growing in the southern Appalachian Mountains by assessing the relationship between tree growth, climate, disturbance, and species interactions near the center and margins for several dominant tree species. Annually resolved dendroecological data will be used to conduct comprehensive analyses of spatial and temporal variability in tree-growth response and forest-stand dynamics over decades to centuries. The overall goals of this research are to evaluate the impact of climate and disturbance processes on the composition, structure, and dynamics of Appalachian oak-pine forests and to determine if these impacts vary relative to the position within geographic ranges. Forest inventory and tree-ring data collected from sites located in national forests, national parks, and private forest reserves throughout the central and southern Appalachian Mountains will used to compare patterns of tree establishment, growth, and mortality near the center and margins of several species ranges. These comparisons will provide information regarding the factors that limit the geographic distribution of these tree species and how the ranges of the tree species are likely to change in response to climate and disturbance.Analyzing the relative importance of climate and disturbance on vegetation dynamics of these sites will increase basic understanding of the limits to species distributions and inform conservation efforts aimed at predicting and mitigating the response of tree species to climate change. Dramatic changes in species distributions caused by climate change have been documented and are projected to continue in response to rapid global warming. Climate change poses numerous threats to ecosystem health, including loss of biodiversity, spread of exotic species, and extinction of species. Mitigation of these threats requires an understanding of the mechanisms that influence the structure and dynamics of species ranges. This project will provide information concerning factors that limit the geographical distribution of Appalachian tree species near their southern range boundary and enable more accurate projections of species range dynamics to be modeled. 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.