Long-term phenological changes in tundra plants in response to experimental warming and observed changes in climate

• Steven Oberbauer
• Tiffany Troxler

Abstract
Arctic regions are predicted to undergo strong warming in coming decades, and they have already undergone measurable warming within recent decades. A coordinated international experiment on the effects of warming on the phenology and growth of individual tundra species and on plant communities, the International Tundra Experiment (ITEX), started in 1990 to directly measure the ways in which tundra plants and communities respond to consistent, lowlevel increases in temperature across the tundra biome. Tundra systems are clearly capable of responding to climate warming on fairly short time scales, without artificial increases in nutrients, and these changes will have significant impacts regionally and globally. One aspect of tundra plants that is highly sensitive to slight changes in temperature is phenology, the timing of key life-history events such as bud burst, leaf growth, flowering etc. The species phenology, growth and community data analyzed to date show responses that in many ways mirror patterns seen along climate gradients, but changes are too subtle and too variable to be detected by most individual-site studies, some after more than a decade of warming. ITEX as an observing network provides a unique opportunity to evaluate plant phenology changes at a global scale across the tundra biome. In this working group we will evaluate changes in plant phenology across the tundra biome over the past 10-15 years in two ways: 1) controls plots versus plots subject to long-term experimental warming, and 2) phenology of controls measured during the mid 1990s with controls remeasured during the recent International Polar Year field season. The primary request of this working group proposal is for access to facilities and expertise at NCEAS, as we can provide much of the support for participants.