Doctoral Dissertation Research: Biogeography of Island Flora in the Georgian Bay, Lake Huron, Ontario

物种-岛屿关系的概念起源于海洋环境中的岛屿，并已被广泛应用于岛屿。生物地理学家和生态学家在研究岛屿上的物种丰富度时，最常考察的因素之一是岛屿与殖民者来源地之间的相对和绝对距离，以及被检查的岛屿面积。最近的研究强调了有效距离、岛屿形态、环境异质性、干扰、物种相互作用和植被动态等因素可能发挥的作用。这一博士论文研究项目将通过分析淡水环境中的岛屿，特别是影响乔治亚湾东岸马萨索加省公园内岛屿植被时空变化的因素，扩大岛屿生物地理学概念的应用。需要解决的研究问题包括：物种面积关系和物种距离关系是否适用于马萨索加群岛？除了面积和距离外，还有什么中介因素会影响岛屿上的物种丰富度？森林年龄级结构是否有助于确定物种丰富度是否存在长期平衡，或者植被的当前特征是否仅代表动态变化过程中的一个阶段？为了回答这些问题，草本植物和木本植物物种丰富度将通过分层随机抽样在50个岛屿上的两个1米带样带上确定。在沿样带随机居中的100米平方样方内，将按树种记录树木、树苗和苗木的数量。样方内所有树木的直径将被记录下来，并将从这些树木的子集中提取树木核心。底物质地、酸碱度和基岩深度将从样方中心记录下来。将使用地形图和水文图来测量岛屿的大小和周长、岛屿距离和地形变异性。将使用距离变量、主要大气模式、湖流和岛屿密度(即垫脚石)来确定有效距离。岛的形状将按周长/面积比计算。将为整个数据集和由森林、灌木和草本物种组成的子集计算因变量物种丰富度。比率水平的自变量将使用多元回归检验其对物种丰富度的相对影响。简单的回归将被用来建立直径和树龄之间的关系，以便估计所有采样树木的树龄。将绘制每个岛屿上不同年龄段的林分地块，以帮助确定优势物种是否正在自我繁殖。这将使人们能够推断在生态时间尺度内改变物种优势的可能性，从而改变物种丰富度的可能性。调查影响马萨索加公园物种丰富度的可测量因素将进一步了解淡水环境中的岛屿生物地理概念。通过将森林动态的时间维度作为当前物种丰富度的稳定性或无常的指标，拟议的研究结果将可推广到更广泛的生态变化问题。这项研究将为管理官员提供有关岛屿植被和生物多样性的基线数据和洞察。研究成果还将涉及乔治亚湾海岸线，包括马萨索加群岛目前的生态完整性问题。计划采取两项举措(安大略省的遗产海岸项目和三万个岛屿联合国生物圈保护区提案)，在该区域开展生态旅游和发展活动，这将增加岛屿的使用。不断增加的人类压力可能最终会导致这些岛屿的物种丰富度和组成发生变化。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。

Concepts of species-island relationships originated in and have been widely applied to islands in marine environments. Among the factors most often examined biogeographers and ecologists exploring variations as they examine species richness on islands have been the relative and absolute distances separating islands from sources of colonists and the area of the islands under examination. More recent studies have highlighted the possible role that factors like effective distance, island morphology, environmental heterogeneity, disturbance, species interactions, and vegetation dynamics may play. This doctoral dissertation research project will expand the application of island biogeography concepts through analysis of islands in freshwater environments, particularly the factors influencing spatial and temporal variation of island vegetation within the Massasauga Provincial Park on the eastern shore of the Georgian Bay. Among the research questions to be addressed are: Do species-area and species-distance relationships apply in the Massasauga islands? What mediating factors besides area and distance affect species richness on the islands? Do forest age-class structures help determine whether there is a long-term equilibrium of species richness, or do current characteristics of vegetation represent only one stage in a process of dynamic change? To answer these questions, herbaceous and woody species richness will be determined along two 1-m-belt transects on each of 50 islands selected through stratified random sampling. Within 100-m-squared quadrats centered randomly along the transects, the number of trees, saplings, and seedlings will be recorded by species. The diameter of all trees within the quadrats will be recorded, and tree cores will be taken from a subset of those trees. Substrate texture, pH, and depth to bedrock will be recorded from the center of the quadrats. Topographic maps and hydrographic charts will be used to measure island size and perimeter, island distances, and topographic variability. Distance variables, prevailing atmospheric patterns, lake currents, and island density (i.e. stepping stones) will be used to determine effective distance. Island shape will be calculated as a perimeter/area ratio. The dependent variable, species richness, will be calculated for the overall data set and for subsets consisting of forest, shrub, and herbaceous species. The ratio-level independent variables will be tested for their relative impact on species richness using multiple regression. Simple regression will be used to establish relationships between diameters and age in order to estimate ages for all of the sampled trees. Age-class plots of stands on each island will be drawn to help determine whether or not dominant species are reproducing themselves. This will allow inferences to be made about the possibility of changing species dominance and therefore of changing species richness within ecological time scales. Investigating measurable factors influencing species richness of Massasauga park will further understanding of island biogeographic concepts in freshwater settings. By incorporating a temporal dimension of forest dynamics as an indicator of the stability or impermanence of current species richness, the results of the proposed research will be generalizable to broader issues of ecological change. This research will provide management officials with baseline data and insight regarding island vegetation and biodiversity. Research results will also pertain to current issues concerning the ecological integrity of the Georgian Bay shoreline, including the Massasauga islands. Two initiatives (Ontario's Heritage Coast Project and the Thirty Thousand Islands United Nations Biosphere Reserve proposal) are planned to generate eco-tourism and development activities in the region, which would increase island use. Increasing human pressures may eventually lead to shifts in the species richness and composition of the islands. 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.