Postglacial vegetation history of Orcas Island, northwestern Washington

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• 作者：Estella B. Leopold^a ; Peter W. Dunwiddie^a ; ^{pdunwidd@u.washington.edu" class="auth_mail" title="E-mail the corresponding author} ; Cathy Whitlock^b ; Rudy Nickmann^c ; William A. Watts^d ; ¹
• 关键词：Island biogeography ; Postglacial pollen ; Northern Puget Lowland ; Bison antiquus habitat ; San Juan Islands
• 刊名：Quaternary Research
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：85
• 期：3
• 页码：380-390
• 全文大小：2185 K

文摘

The revegetation of islands following retreat of Pleistocene glaciers is of great biogeographical interest. The San Juan Islands, Washington, feature regionally distinctive xerophytic plant communities, yet their vegetation history, as it relates to past climate and sea level, is poorly known. We describe a 13,700-year-old pollen record from Killebrew Lake Fen and compare the vegetation reconstruction with others from the region. The data suggest that the narrow channels surrounding Orcas Island were not a barrier to early postglacial immigration of plants. Between 13,700 and 12,000 cal yr BP, Pinus, Tsuga, Picea, Alnus viridis, and possibly Juniperus maritima were present in a mosaic that supported Bison antiquus and Megalonyx. The rise of Alnus rubra-type pollen and Pteridium spores at ca. 12,000 cal yr BP suggests a warming trend and probably more fires. Temperate conifer taxa, including Cupressaceae, Pseudotsuga, Tsuga heterophylla, and Abies, increased after 11,000 cal yr BP and especially in the last 7000 cal yr BP. After 6000 cal yr BP, Pseudotsuga and Cupressaceae dominated the vegetation. The last 1500 yr were the wettest period of the record. Due to its rain shadow location, Orcas Island experienced drier conditions than on the mainland during most of the postglacial period.