Forests communities in transition: Eocene fossil sites from western and Arctic Canada

北美 地质历史上的温带森林与东方有许多植物属。 亚洲和欧洲(如太子松、枫属、梧桐属和杜鹃花属)。 这些地理区域之间的交流在今天是不可能的，因为 扩散走廊在300万到1500万年前就已经太冷了。气候变暖 然而，地质过去的插曲促进了生物之间的交换 他们。化石记录提供了植物分类群存在的初步记录 以及过去的气候。拟议的工作将集中在始新世早期 北美洲大部分地区支持热带动物群的时期(约56-47.8年 植物区系、中纬度年平均气温(MAT)约为20°C，温和 没有霜冻的冬天，甚至北极也有鳄鱼。这些温暖的高空 纬度早始新世气候为植物和 动物通过北极。不列颠哥伦比亚省的化石所在地是唯一 北极以外加拿大始新世的记录--从凉爽(垫子) 10-12°C)高地湖泊，支持混合温带森林 和热带生物群，到温暖(MAT 15-20℃)的太平洋低地环境 公元前和西澳的海岸，包括棕榈树。拟议的研究计划有以下几点 长期目标：(1)综合森林社区的变化 通过时间，即优势、多样性和首次出现(起源于 谱系)；(2)确定区域和 生物多样性的时间模式及其与气候变化的关系， 即过去气候变化的生物后果和气候作为 进化的驱动力。短期目标侧重于：(1)McAbee 在公元前其他地方重建化石床和目标地点 古环境；(2)完成对北极现有集合的分析 始新世遗址；以及(3)对这些遗址的系统分析 机遇号允许包括从不列颠哥伦比亚省到 在时间和空间上扩大范围，以涵盖公元前更多的地区。化石 不列颠哥伦比亚省的地点将沿着层面进行抽样，以隔离森林社区 在时间上是分开的。这些化石遗址在地层上是相互关联的 放射性测量可测年的火山灰，将所有化石研究地点 按时间顺序排列。通过记录每一块可识别的化石 我们将在以下地点重建气候、森林组成和多样性 生态时间尺度。详细的系统分析的目标是 BC遗址丰富的树叶、花朵和种子化石记录将确定关键 植物科和属，并有可能阐明这些植物的首次出现 由于这些始新世遗址富含重要的温带和亚热带 植物家族。这项研究将提供数据，帮助理解森林 社区对过去的全球变暖以及对 现代温带生态系统。

North American temperate forests in the geological past shared many plant genera with east Asia and Europe (e.g. Pseudolarix, Acer, Sassafras, and Trochodendron). Exchange between these geographic regions is not possible today as the dispersal corridors have been too cold for 3-15 million years. Climate warming episodes in the geological past, however, facilitated biotic exchange between them. The fossil record provides a primary record of the presence of plant taxa and of climate in the past. The proposed work will focus on the early Eocene epoch (ca. 56-47.8 MYA) when much of North America supported a tropical fauna and flora, mid-latitude mean annual temperatures (MAT) were ca. 20°C with mild frost-free winters, and even the Arctic hosted alligators. These warm high latitude early Eocene climates opened a northern dispersal route for plants and animals via the Arctic. Fossil localities in British Columbia present the only record of the Eocene from Canada outside the Arctic - ranging from cool (MAT 10-12°C) elevated upland lake sites that supported forests of mixed temperate and tropical biota, to warm (MAT 15-20°C) lowland environments on the Pacific coast of BC and WA that included palms. The proposed research program has these long term objectives: (1) Develop a synthesis of changes in forest communities through time, i.e., dominance, diversity and first appearances (origination of lineages), both within and between fossil sites; (2) Determine regional and temporal patterns of biotic diversity, and its relation to change in climate, i.e. the biotic consequences of past climate change and climate as an evolutionary driver. Short term objectives are focused on: (1) the McAbee fossil beds and targeted sites elsewhere in BC to reconstruct paleoenvironments; (2) completion of analyses of existing collections of Arctic Eocene sites; and (3) systematic analysis of these sites expanding as opportunity allows to include other plant fossil sites from British Columbia to broaden the scope both temporally and spatially to cover more of BC. Fossil sites in BC will be sampled along bedding planes to isolate forest communities separated in time. These fossil sites are stratigraphically correlated using radiometrically datable volcanic ashes, placing all of the fossil study sites into a chronological sequence. By documenting every identifiable fossil collected we will reconstruct climate, forest composition, and diversity at ecological time scales. The objective for detailed systematic analyses of the BC sites rich record of fossil leaves, flowers and seeds will identify key plant families and genera and potentially clarify first appearances of these taxa as these Eocene sites are rich in important temperate and subtropical plant families. This study will provide data that helps understand how forest communities responded to past global warming as well as on the emergence of modern temperate ecosystems.