Cooperative Ecosystem Studies Unit, Rocky Mountain CESU

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The U.S. Geological Survey¿s Fort Collins Science Center (USGS) is offering a funding opportunity to a CESU partner for research on climate reconstruction from tree rings of Populus (cottonwood and poplar) in the western United States and western China. Shifts in river flows are a central impact of climate change. Along snowmelt rivers in interior western North America, increases in winter and spring temperatures are beginning to cause increased winter flows, earlier snowmelt peaks, smaller annual peaks, and decreased summer low flows. These shifts threaten agricultural and municipal water supplies, especially in dry regions. In addition, because flow timing and magnitude are central to the functioning of riverine ecosystems, these shifts affect the abundance of many native species and provide opportunities for spread of already dominant invasive species. Therefore, monitoring of flow variation is central to assessment of the effects of global change to water supplies and riverine ecosystems on federal lands. The effects of human-induced climate change on river flow cannot be understood, however, unless they can be distinguished from the effects of natural climate variation and water management. Fluctuations in climate over the last century have caused flow shifts similar in magnitude to the effects of construction of major reservoirs. Therefore, there is a great need for studies of climate and flow variation over the last few centuries to assist in detecting and adapting to effects of global change. Because stream-gage records are, at most, about 100 years long, other techniques, including tree-ring analysis, must be developed to extend those records. This need is especially great in relatively treeless areas like the Great Plains where knowledge of past climate is limited by the scarcity of old trees. Ongoing work by USGS has demonstrated the feasibility of using Populus ring width to reconstruct flow along perennial meandering rivers of the Great Plains. The purpose of this funding opportunity is to test the feasibility of expanding this approach to other ecosystems in three ways.

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