1. Vegetation Shift in the Pan-Arctic Tilmann Silber & Daniel Angst 2.3.20091Topics in Ecosystem Ecology FS2009

2. Introduction Climate Warming: 2°C per decade for the last 30 years in the Arctic Evidence for shift in land surface vegetation on a local scale. alteration of surface energy balance alteration of carbon balance change in hydrology 2.3.2009Topics in Ecosystem Ecology FS20092 -> also on a larger scale?

3. Fillol & Royer, 2003 monitoring of ecotone Taiga/Tundra movement in Canada with remote sensing data Data Basis: NDVI, Surface Temperature (T s ) 2.3.2009Topics in Ecosystem Ecology FS20093

4. Remote Sensing AVHRR Sensors on NOAA Satellites Normalized Difference Vegetation Index NDVI = (a NIR – a V )/(a NIR + a V ) T s : Land surface temperature 2.3.2009Topics in Ecosystem Ecology FS20094 NOAA HRPT – 28.7.2008 http://www.wetter-welt.de/

5. Theoretical Framework 2.3.2009Topics in Ecosystem Ecology FS20095 hydric Regime radiative Regime Ecotone

6. Results / Conclusion 2.3.2009Topics in Ecosystem Ecology FS20096

7. Tape et al. 2006 Goal: upscale evidence for shrub expansion to pan-Arctic level Combining three lines of evidence: – Repeated photography in Alaska: ca. 1949 – 2001 – Review of plot studies & NDVI studies 2.3.20097Topics in Ecosystem Ecology FS2009

8. Repeated Photography Detection of shrubs > 0.5 m Covers predominantly river valleys 1949 2001 2.3.20098Topics in Ecosystem Ecology FS2009

9. Results photography 2.3.20099Topics in Ecosystem Ecology FS2009 Disturbances!

10. Plot & NDVI studies Plot studies – Consistent trend for increase in shrub coverage – Covers shrubs < 0.5m NDVI studies: consistently increasing values in Alaska and the Arctic 2.3.200910Topics in Ecosystem Ecology FS2009

11. Critical: interpreting NDVI values Higher shrub coverage! Longer growing season!  Authors: Both 2.3.200911Topics in Ecosystem Ecology FS2009

12. Can it be upscaled? Yes: Alaska Canada Uncertain (?): Scandinavia Sibiria  To be discussed! 2.3.200912Topics in Ecosystem Ecology FS2009

13. When did it start? Application of a logistic growth model to the data Calculation of starting point: ca. 1875 – 1925 (very rough) Literature: current warming in Alaska started about 1970  Little Ice Age? (Last minimum ~ 1850; cooling less than 1°C) 2.3.2009 13Topics in Ecosystem Ecology FS2009

14. Discussion Consistent shift in both studies What fraction of change is accountable to recent warming? (ecologic equilibrium?) High shrub expansion in valleys due to nutrients? Data hardly quantifyable  how to assess the effects of shrub expansion at global scale? 2.3.200914Topics in Ecosystem Ecology FS2009

15. References Fillol, E.J. & Royer, A., 2003. Variability analysis of the transitory climate regime as defined by the NDVI/Ts relationship derived from NOAA-AVHRR over Canada. In: Proceedings 2003 IEEE International, Geoscience and Remote Sensing Symposium, IGARSS '03, 21-25 July, pp. 2863-2865. Tape, K., M. Sturm and C. Racine, 2006. The evidence for shrub expansion in Northern Alaska and the Pan-Arctic. Global Change Biol., 12(4): 686-702. 2.3.2009Topics in Ecosystem Ecology FS200915

16. Thank you!