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

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

3. Study Sites Barrow 71°18’N, 156°40’W Atqasuk 70°29’N, 157°25’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

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 L. arctica Hulten (1968) 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) Average Temperature (°C) Julian Day

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

11. Inflorescence Height

13. Luzula confusa

14. Inflorescence Height Luzula confusa

15. Inflorescence Height Luzula confusa

16. Inflorescence Height Luzula arctica

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

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

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