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Collaborative Study of Arctic Ecosystem Changes: Insights from the International Tundra Experiment

The International Tundra Experiment (ITEX) investigates the effects of climate change on Arctic and alpine tundra ecosystems. Initiated in 1990, ITEX conducts experiments focusing on passive warming using Open Top Chambers (OTCs) to measure changes in vegetation phenology, community structure, and ecosystem dynamics. With sites across Greenland, Alaska, and the Tibetan Plateau, ITEX produces long-term data that reveal significant trends: warmer conditions lead to taller, shrubbier communities and altered carbon dynamics in wet versus dry areas.

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Collaborative Study of Arctic Ecosystem Changes: Insights from the International Tundra Experiment

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  1. Collaborative Research:Study of Arctic ecosystem changes in the IPY using the International Tundra Experiment (ITEX) Steve Oberbauer, Robert Hollister*,Jeff Welker, Julia Klein, William Gould, Patrick Sullivan, Bartmar Sveinbjornsson, Keith Boggs, & Caroline Lewis

  2. What is ITEX? • International Network of experiments • Focus on climate change impacts on tundra vegetation of Arctic and Alpine (recently Antarctic) • Formalized 1990, earliest sites initiated 1992 • Primary experiment: passive warming (1-2 ºC) with Open Top Chambers (OTCs), non-destructive measurements. • Networking (16 workshops) • Standard protocols (ITEX manual) • Outputs • Phenology (synth. workshop 1996, publ. 1997, 1999) • Community (synth. workshop 2001, publ. 2005, 2006 • Ecosystem (synth. publ. 2007)

  3. ITEX sites directly and collaboratively involved with this project (Southern Australian and Switzerland sites not shown).

  4. 1 Thule, Greenland • 2 Barrow, Alaska • 3 Atqasuk, Alaska • 4 Toolik, Alaska • 5 Tibetan Plateau, China • 6 Niwot Ridge, Colorado

  5. Project components • Phenological Change (weekly, 2007, 2008) • Compare control vs. warmed, current vs. past • Remeasurement of first green leaf, flowering & seed set and progression of growth & reproductive effort • Community Change (once peak season, 2007 or 08 ) • Compare control vs. warmed, current vs. past • Remeasurement of ITEX plots and km2 grids at Toolik & Imnavait Creek using point framing • Ecosystem change (once peak season, 2007 or 08 ) • Compare control vs. warmed • Reflectance measurements of cover/biomass (NDVI) and photosynthetic physiology (PRI) • Leaf, litter, and soil nutrients • Leaf and litter isotopes (13C, 15N, 18O) • Leaf secondary compounds (tannins and lignins) • Radiocarbon of soil respiration (age of carbon leaving soil)

  6. Synthesis workshops • Phenological change 2008 • Community change 2009

  7. Data management • Data collection: all non real-time • Limited sites-weekly: plant phenology, plot reflectance • Cross sites-peak season: reflectance; point-quadrat plot canopy structure and composition; nutrients and isotopes of leaves, litter, and soil; leaf tannins and lignins; respiratory and soil radiocarbon • Data Screening: Data double checked/ outlier/visualization screening • Metadata: JOSS format • Data archiving: NSIDC

  8. Major results • OTC approach validated with natural climate variation • Phenology changes with small temperature increase • Controls are changing with background • Community changes toward taller, shrubbier with warming • Wet sites accumulate carbon, dry sites release carbon with warming

  9. The value of ITEX for IPY • Stable network, broad international coverage • Long-term data 10-15 years for some. • Experimental changes • Changes on Controls • Detailed vegetation analysis • Ecosystem • Nondestructive (repeated measures)

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