Dynamic treeline and cryosphere response to pronounced mid- Holocene climatic variability in the US Rocky Mountains

• 成果类型: Article
• 署名作者: Pederson, Gregory T.; Stahle, Daniel; Mcwethy, David B.; Toohey, Matthew; Jungclaus, Johann; Lee, Craig; Martin, Justin; Alt, Mio; Kichas, Nickolas; Chellman, Nathan; Mcconnell, Joseph R.; Whitlock, Cathy
• 署名单位: United States Department of the Interior; United States Geological Survey; Montana State University System; Montana State University Bozeman; University of Saskatchewan; Max Planck Society; Montana State University System; Montana State University Bozeman; Nevada System of Higher Education (NSHE); Desert Research Institute NSHE
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12265
• DOI: 10.1073/pnas.2412162121
• 发表日期: 2025-01-14
• 关键词: temperature; rings; wood; reconstructions; vegetation; patterns; IMPACT; GROWTH; island; depth

摘要

Climate-driven changes in high-elevation forest distribution and reductions in snow and ice cover have major implications for ecosystems and global water security. In the Greater Yellowstone Ecosystem of the Rocky Mountains (United States), recent melting of a high- elevation (3,091 m asl) ice patch exposed a mature stand of whitebark pine (Pious albicaulis) trees, located similar to 180 m in elevation above modern treeline, that date to the develop tree-ring- based temperature estimates for the upper-elevation climate conditions that resulted in ancient forest establishment and growth and the subsequent regional ice- patch growth and downslope shift of treeline. Results suggest that mid-Holocene forest establishment and growth occurred under warm-season (May-Oct) mean temperatures of 6.2 degrees C (+/- 0.2 degrees C), until a multicentury cooling anomaly suppressed temperatures below 5.8 degrees C, resulting in stand mortality by c. 5,440 y BP. Transient climate model simulations indicate that regional cooling was driven by changes in summer insolation and Northern Hemisphere volcanism. The initial cooling event was followed centuries later (c. 5,100 y BP) by sustained Icelandic volcanic eruptions that forced a centennial-scale 1.0 degrees C summer cooling anomaly and led to rapid ice-patch growth and preservation of the trees. With recent warming (c. 2000-2020 CE), warm-season temperatures now equal and will soon exceed those of the mid-Holocene period of high treeline. It is likely that perennial ice cover will again disappear from the region, and treeline may expand upslope so long as plant-available moisture and disturbance are not limiting.