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

在过去的地质时期，北美 * 温带森林与东亚 * 和欧洲共享许多植物属（例如，Pseudolarix，Acer，Sassafras和Trochodendron）。这些地理区域之间的交换在今天是不可能的，因为扩散走廊已经太冷了300万到1500万年。然而，过去地质时期的气候变暖事件促进了它们之间的生物交换。化石记录提供了过去植物分类群和气候存在的原始记录。拟议的工作将集中在早始新世 * 时代（约。56-47.8百万年），当北美大部分地区支持热带动物群 * 和植物群时，中纬度年平均温度（MAT）约为2.5 - 3.5百万年。20°C，冬季温和无霜，甚至北极也有短吻鳄。始新世早期温暖的高纬度气候为动植物经由北极向北方扩散开辟了一条路线。不列颠哥伦比亚省的化石地点提供了加拿大在北极以外始新世的唯一记录-从支持温带和热带混合生物群森林的凉爽（MAT*10-12°C）高地湖泊到BC和WA太平洋 * 海岸的温暖（MAT 15-20°C）低地环境，包括棕榈树。拟议的研究计划有这些 * 长期目标：（1）开发一个综合的变化，在森林群落 * 随着时间的推移，即，优势，多样性和第一次出现（* 谱系的起源），在化石遗址内和之间;（2）确定生物多样性的区域和时间模式，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驱动力。短期目标集中在：（1）McAbee化石层和不列颠哥伦比亚省其他地方的目标遗址，以重建古环境;（2）完成对北极始新世遗址现有收藏品的分析;（3）对这些遗址进行系统分析，以便有机会将不列颠哥伦比亚省的其他植物化石遗址包括在内，从而在时间和空间上扩大范围，覆盖更多的不列颠哥伦比亚省。将沿沿着对不列颠哥伦比亚省的化石 * 地点进行取样，以隔离在时间上分开的森林群落 *。这些化石地点是地层相关使用 * 放射性测年火山灰，把所有的化石研究地点 * 到一个时间顺序。通过记录收集到的每一个可识别的化石，我们将在生态时间尺度上重建气候、森林组成和多样性。详细系统分析公元前遗址的化石叶，花和种子的丰富记录的目标将确定关键的植物科和属，并可能澄清这些分类群的首次出现，因为这些始新世遗址富含重要的温带和亚热带植物科。这项研究将提供数据，帮助了解森林群落如何应对过去的全球变暖以及现代温带生态系统的出现。

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.***