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

点击翻译按钮获取中文摘要

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.***