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Long-Term Response of Luzula arctica and Luzula confusa to Warming in the Alaskan Tundra

Long-Term Response of Luzula arctica and Luzula confusa to Warming in the Alaskan Tundra. Why Arctic?. Linked to global climate (ACIA 2004). Expected to show earliest and greatest response to global climate change (IPCC 2007). Study Sites. Barrow 71°18’N, 156°40’W. Experimental Design

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Long-Term Response of Luzula arctica and Luzula confusa to Warming in the Alaskan Tundra

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  1. Long-Term Response of Luzula arctica and Luzula confusa to Warming in the Alaskan Tundra

  2. Why Arctic? • Linked to global climate (ACIA 2004) • Expected to show earliest and greatest response to global climate change (IPCC 2007)

  3. Study Sites Barrow 71°18’N, 156°40’W • Experimental Design • 2 Dry Heath Communities: • Atqasuk Dry • Barrow Dry • 1 Meter squared plots • -24 Control • -24 Warmed • Passive open-top fiberglass chambers • Increase temperature 1-3° C Atqasuk 70°29’N, 157°25’W

  4. Luzula arctica and Luzula confusa • Common rushes at both dry heath sites • Associated with disturbances • Known to hybridize

  5. Measurements Summer 1994-2010 - Inflorescence Height- Number of Inflorescences- Flowering date Inflorescence Height L. arctica Hulten (1968)

  6. Inflorescence Height

  7. Inflorescence Height

  8. Question: • What factor is causing a negative response in these years? Relate to temperature: Thawing Degree Days (TDD)- cumulative degree days above freezing (0°C)

  9. Thawing Degree Days (TDD) Thawing Degree Days (TDD) AverageTemperature (°C) Julian Day

  10. Thawing Degree Days (TDD) Thawing Degree Days (TDD) AverageTemperature (°C) Julian Day

  11. Inflorescence Height

  12. Inflorescence Height

  13. Inflorescence Height Luzula confusa

  14. Inflorescence Height Luzula confusa

  15. Inflorescence Height Luzula confusa

  16. Inflorescence Height Luzula arctica

  17. Inflorescence Height Luzula arctica Increase in height with increasing TDD in control plots No change in warmed plots

  18. Summary Luzula confusa Luzula arctica Inflorescence Height Overall: Increased TDD is associated with increased height. All sites/treatments suggest increased height with increased TDD. Inflorescence Height Overall: Increased TDD is associated with increased height. All sites/treatments show no trend.

  19. Number of Inflorescences Luzula confusa

  20. Number of Inflorescences Luzula confusa Fewer inflorescences in warmed plots at both sites

  21. Number of Inflorescences Luzula arctica

  22. Number of Inflorescences Luzula arctica No significant change

  23. Summary Luzula confusa Luzula arctica Inflorescence Height Overall: Increased TDD is associated with increased height. All sites/treatments suggest increased height with increased TDD. Inflorescence Height Overall: Increased TDD is associated with increased height. All sites/treatments show no trend. Number of Inflorescences Overall: No trend. Control plots had more inflorescences than warmed plots. Number of Inflorescences Overall: increased TDD is associated with decreased number of inflorescences. All sites/treatments show no trend.

  24. Flowering Date Luzula confusa Earlier flowering date in warmed plots Flowering is earlier in Atqasuk

  25. Flowering Date Luzula arctica Flowering is earlier in Atqasuk

  26. Summary Luzula confusa Luzula arctica Inflorescence Height Overall: Increased TDD is associated with increased height. All sites/treatments suggest increased height with increased TDD. Inflorescence Height Overall: Increased TDD is associated with increased height. All sites/treatments show no trend. Number of Inflorescences Overall: No trend. Control plots had more inflorescences than warmed plots. Number of Inflorescences Overall: increased TDD is associated with decreased number of inflorescences. All sites/treatments show no significant change. Flowering Date • Flowering occurs earlier with warming. Flowering Date No significant change.

  27. Conclusions • Both species are responding to warming • Each species responds differently • Response is different for each site

  28. Future Plans • Continue to look at other relationships. • What other factors are involved? • More phenology

  29. Questions? Acknowledgements: National Science Foundation GVSU Arctic Ecology ProgramJeremy May, Robert Slider, Jennifer Liebig Barrow Arctic Science Consortium References: IPCC (ed) 2007. Climate Change 2007: The Scientific Basis. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. Cambridge, United Kingdom. pp. 230 ACIA 2004. Impacts of a Warming Arctic: Arctic Climate Impact Assessment. Cambridge University Press. Cambridge, United Kingdom. Hollister, R.D., P.J. Webber, and C. Bay.  2005.  Plant response to temperature in northern Alaska: Implications for predicting vegetation change.  Ecology. 86(6): 1562-1570.

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