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

北美 在过去的地质时期，温带森林与东部森林有许多植物属， 亚洲和欧洲（例如，Pseudolarix，Acer，Sassafras和Trochodendron）。 这些地理区域之间的交流今天是不可能的， 扩散走廊在300万到1500万年里都太冷了。气候变暖 然而，地质历史中的事件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原始记录 和过去的气候。拟议的工作将集中在始新世早期 epoch（纪元）5647.8 MYA），当时北美大部分地区都支持热带动物群 植物群、中纬度年平均温度（MAT）约为1.5 ℃。20 ℃，轻度 冬天无霜，甚至北极也有短吻鳄。这些温暖的高 纬度始新世早期的气候为植物开辟了一条北方的传播路线， 动物通过北极。不列颠哥伦比亚省的化石地点是唯一 加拿大在北极以外的始新世的记录-从冷（MAT 1012 C）支持混合温带森林的高地湖泊遗址 和热带生物群，到太平洋温暖（MAT 1520 C）的低地环境 包括棕榈树的BC和WA海岸。拟议的研究计划有这些 长期目标：（1）编制森林群落变化综合报告 通过时间，即，优势，多样性和首次出现（起源 （2）确定区域性和 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主要集中在：（1）McAbee 化石床和目标地点在公元前其他地方重建 （2）完成对现有北极古环境的分析 始新世遗址;以及（3）对这些遗址的系统分析， 机会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，以覆盖更多的BC。化石 将沿沿着层面对不列颠哥伦比亚省的地点进行采样，以隔离森林群落 在时间上分开。这些化石地点是地层相关使用 放射性测定法确定年代的火山灰，将所有的化石研究地点 按时间顺序排列通过记录每一块可识别的化石 我们将重建气候，森林组成和多样性， 生态时间尺度详细系统分析的目标是 公元前遗址丰富的化石记录叶，花和种子将确定关键 植物科和属，并可能澄清这些首次出现 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，帮助了解如何森林 社区对过去的全球变暖以及 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. 5647.8 MYA) when much of North America supported a tropical fauna and flora, mid-latitude mean annual temperatures (MAT) were ca. 20C 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 1012C) elevated upland lake sites that supported forests of mixed temperate and tropical biota, to warm (MAT 1520C) 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.