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Physioecological mechanism of the alpine treeline dynamics under global climate change

The 2 nd Third Pole Environment Workshop Kathmandu, Oct. 26 – 28, 2010. Physioecological mechanism of the alpine treeline dynamics under global climate change. Dr. Mai-He Li. Swiss Federal Research Institute WSL. E-mail : maihe.li@wsl.ch. Definition of the alpine treeline

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Physioecological mechanism of the alpine treeline dynamics under global climate change

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  1. The 2nd Third Pole Environment Workshop Kathmandu, Oct. 26 – 28, 2010 Physioecological mechanism of the alpine treeline dynamics under global climate change Dr. Mai-He Li Swiss Federal Research Institute WSL E-mail: maihe.li@wsl.ch

  2. Definition of the alpine treeline Driving forces of treeline formation Upword shifts of the alpine treelines, corresponding to global warming, in the Himalayas and worldwide Physioecological machanisms of the alpine treeline shifts Conclusions

  3. 9 3 2 10 12 5 4 15 11 13 14 6 1 7 16 17 8 18 20 19 Treelines across the globe ---a virtual site visitation The Himalayas Davos, Swiss Alps

  4. Ch Koerner, J Paulsen 2004

  5. Kyi Chu, North of Lhasa 29°42‘ N, 96°45 ‘ E Miehe et al. 2007. Mountain Res. & Develop. 27, 169-173

  6. Factors affecting trees at the alpine treelines Holtmeier & Broll, 2009. Polarforschung 79, 139-153

  7. The alpine treeline position is very closely correlated to the 10°C isotherm for the warmest month The temperature at the alpine treelines varied from 6 to 13°C (±500 m in treeline elevation) Koeppen 1923; Aulitzky 1961 Wu 1983; Oshawa 1990

  8. A global mean of 6.7 °C soil temperature (-10 cm depth) for growing season at treeline 8 2 2 6.7 ± 0.8 °C 12 1 T 2 n=2 6 6 3 Seasonal mean temperature, T (°C) 4 G 300 200 2 Growing period G (d) 100 0 0 70 60 50 40 30 20 10 0 10 20 30 40 N Latitude (°C) S Ch Körner, J Paulsen (2004) J Biogeogr 31:713-732

  9. Predicting changes in temperature Source: Massachusetts Ave, Cambridge MA It is predicted that the temperatures in the Indian sub-continent will rise between 3.5 and 5.5°C by 2010, and on the Tibetan Plateau by 2.5°C by 2050, and 5°C by 2010 Kumar et al. 2006

  10. Dupouey et al. 1997 Each species is likely to respond to climate change in its own way:

  11. Treelineformation Global drivers 'general principle' Regional drivers 'modulation' General physioecological explanation Local environmental explanations

  12. Environmental explanation of treeline • (1) Thestresshypothesis • (2) Thematuration time hypothesis • (3) Thedisturbancehypothesis • Thereproduction/germination • hypothesis Körner Ch (1998) Oecologia 115:445 Li MH, Krauchi N (2005) J.S.For.Tech.26, 36-42 Li MH et al. 2008. Tree Physiology 28, 1287-1296 Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387

  13. Biological explanation of treeline • Thegrowthlimitationhypothesis • Thecarbon balance hypothesis Körner Ch (1998) Oecologia 115:445 Li MH, Krauchi N (2005) J.S.For.Tech.26, 36-42 Li MH et al. 2008. Tree Physiology 28, 1287-1296 Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387

  14. 1. The stress hypothesis • Repeated damage by freezing, frost desiccation or phototoxic effects after frost impair tree growth Tranquillini W.1979. Physiological ecology of the alpine timerline Körner Ch. 1998. Oecologia 115, 445-459 Li MH, Kräuchi N. 2005.J.S.For.Tech. 26, 36-42

  15. 2. The maturation time hypothesis Maturation of leaves,shoots, fruits, and buds e.g. seed maturation of Pinus sylvestris needs at least 600 – 890 GDD (growing degree-days >5°C) Odum 1979 Short growing season Tranquillini W.1979. Physiological ecology of the alpine timerline Körner Ch. 1998. Oecologia 115, 445-459 Li MH, Kräuchi N. 2005.J.S.For.Tech. 26, 36-42

  16. 3. The disturbance hypothesis Mechanic damage by wind, ice blasting, snow break and avalanches, fire……Animal disturbances such as insectFungal pathogensMan-made impacts such as logging, grazing etc. Tranquillini W.1979. Physiological ecology of the alpine timerline Körner Ch. 1998. Oecologia 115, 445-459 Li MH, Kräuchi N. 2005.J.S.For.Tech. 26, 36-42

  17. 4. The reproduction hypothesis Pollination, pollen tube growth, seed development, seed dispersal, germination and seedling establishment Tranquillini W.1979. Physiological ecology of the alpine timerline Körner Ch. 1998. Oecologia 115, 445-459 Li MH, Kräuchi N. 2005.J.S.For.Tech. 26, 36-42

  18. 6. Carbonlimitation 5. Growth limitation Photosynthesis Growth Growth Photosynthesis “Source“ driven “Sink“ driven “Demand“ driven “Supply“ driven Körner Ch (1998) Oecologia 115:445 Li MH et al. 2008. Tree Physiology 28, 1287-1296 Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387

  19. Source limitation hypothesis: Tree growth is considered source limited when carbon assimilation through photo-synthesis is insufficient to meet growth requirements. Sink limitationhypothesis: Treesareconsideredcarbon sink limited whenthereis an abundant supplyoftheresourcesnecessarytosupportgrowth, but growthitselfisdirectly limited byenviron-mental conditions.

  20. 30 100 20 Photosynthesis Net-photosynthesis (%) 50 10 0 Cell doubling time Mitotic time 300 200 Cell doubling time (h) Mitotic time (h) 100 0 0 10 20 30 40 Temperature (°C) Ch Körner (2003) Alpine Plant Life. Springer, Berlin

  21. 4 2 0 4 2 0 4 2 0 Sweden (68° N) Mexico (19° N) Alps (46° N) Pinushartwegii Pinussylvestris Pinuscembra * * Lipids End of winter NSC ** Non-structural carbohydrates + lipids in stem sapwood (% d.m.) Mid season *** Late season Low High Low High Low High G Hoch & C Körner (2003) Oecologia 135:10-21 Altitude

  22. 200 50 50 50 50 160 40 40 40 40 120 30 30 30 30 80 20 20 20 20 40 10 10 10 10 0 0 0 0 0 4360 4360 4360 4360 4360 4360 4550 4550 4550 4550 4550 4550 4810 4810 4810 4810 4810 4810 Polylepistarapacana, VolcanoSajama, Bolivia Leaves Branchwood Stemwood a a a a a ab a a b Starch NSC concentrations (mg cm3) Sugars Elevation (m a.s.l.) NSC=Non-structural carbohydrates = solube sugars + starch G Hoch & Ch Körner (2005) Funct Ecol 19, 941-951

  23. Gas exchange with altitude Acaena cylindrostachya Maximum CO2 assimilation rates 4200 m: 3.9 µ mol/m2 s 3550 m: 5.2 µ mol/m2 s 2900 m: 9.0 µ mol/m2 s Senecio formosus 4200 m: 3.6 µ mol/m2 s 3550 m: 5.8 µ mol/m2 s 2900 m: 7.5 µ mol/m2 s Cabrera HM et al. 1998, Oecologia 114, 145-152

  24. Carbon shortage? - Yes! Piceabalfouriana var. hirtella Li MH et al. 2008. Tree Physiology 28, 1287-1296 Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387

  25. An overalltrend in NSC – 3 treelinesdatapooled A winter C-shortage Li MH et al. 2008. Tree Physiology 28, 1287-1296 Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387

  26. ??? A winter carbon shortage? or An effect of phenological phase-shift? Hoch G. 2003 PhD thesis Uni. Basel

  27. Krummholz Dead individuals Seedlings Adults Tree species line Camarero & Gutierrez (2002) Plant ecology 162: 247 Timberline

  28. General conclusion • The treeline trees may suffer from a winter carbon shortage leading to treeline formation • Global warming leads to increase in treeline elevation to keep pace with climate change • Plantsmay also respondtoclimatechange in Himalayas via • Re-adaptation • Invasions • Extinction Li MH et al. 2006. J Integrat Plant Biology 48, 255 - 259 Li MH et al. 2008. Tree Physiology 28, 1287-1296 Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387

  29. Modeled Climate-Induced Glacier and Vegetation Change in Glacier National Park, 1850-2100 http://www.nrmsc.usgs.gov/images/glacier_animation_slow.gif 30

  30. Podocarpusoleifolius 2550 m a.s.l. 3200 m a.s.l. Espeletianeriifolia 3200 m a.s.l. 2400 m a.s.l. Cavieres et al. 2000. Acta Oecologia 21, 203-211

  31. Abies balsamea Picea rubens Shade needles P<0.05 Sun needles P<0.05 P<0.05 P<0.05 Richardson AD. 2004 Plant & Soil 260, 291-299

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