Beting Forestry Univ.June 11.2011 Formation and dynamies of the alpime treelime Prof.Dr.Mai-He Li )第382海 E-mad maih Treelines 全球高山林线研究简史 Exposure treeline(on coasts,isolated mountains) 形态描述阶段(1920年代之前) (Koppen,Brockmann-Jerosch,Daniker) Wet treeline(on the margins of muskegs bogs) Dry treeline (desert treeline) 现代实验生态研究阶段(1930年代-1970年代) Arctic/Antarctic treeline (Pisek,Larcher,Tranquillini) Cold treeline Alpine treeline 全球变化下的高山林线研究阶段(1980年代始) (Tinner,Korner,Dullinger) Upper treeline vs.low treeline LiMH and KraeuchiN(2005)J Sichan For Technd2664 Rsgaone2o0-2z0mas
1 Beijing Forestry Univ. June 11, 2011 Tree Ecophysiology Group Swiss Federal Research Institute WSL Prof. Dr. Mai-He Li E-mail: maihe.li@wsl.ch Treelines • Exposure treeline (on coasts, isolated mountains) • Wet treeline (on the margins of muskegs & bogs) • Dry treeline (desert treeline) Upper treeline vs. low treeline Arctic / Antarctic treeline • Cold treeline Alpine treeline 全球高山林线研究简史 形态描述阶段 (1920年代之前) (Köppen, Brockmann-Jerosch, Däniker) 现代实验生态研究阶段 (1930年代-1970年代) (Pisek, Larcher, Tranquillini) 全球变化下的高山林线研究阶段(1980年代始) (Tinner, Körner, Dullinger) Li MH and Kraeuchi N (2005) J Sichuan For Sci & Technol 26, 36-42 Pinus cembra treeline ecotone (2100 – 2200 m a.s.l.) in Valais, Switzerland
Alpine zone 0 Morare forest 144 2
2 Picea purpurea treeline ecotone (4100 – 4300 m a.s.l.) in Huang-Long, Sichuan Ch Koerner, J Paulsen 2004 Tree height < 2 or 3 m Tree height > 2 or 3 m Kyi Chu, North of Lhasa 29°42‘ N, 96°45 ‘ E Miehe et al. 2007. Mountain Res. & Develop. 27, 169-173 Factors affecting trees at the alpine treelines Holtmeier & Broll, 2009. Polarforschung 79, 139-153
Environmental conditions 200c vs.high elevations) 50t Lowelevation High olevation 100c 500 10 14 18 20 Soil unde alpine than under treeline trees Treeline:Energy flux in forests and low vegetation JFMAM寸寸ASOND JFMAMJ AS ON D warm Aglobal mean treeline The alpine treeline position is very closely correlated to the 10C e.p isotherm for the warmest month 2。 The temperature at the alpine 2 treelines varied from 6 to 13C (+500 m in treeline elevation) %8083W高96
3 Low elevation High elevation Mean temperature High Low Diurnal variation in temperature Low High Growing season length Long Short Environmental conditions (low elevations vs. high elevations) g g Precipitation Low High Wind Low High Soil quality High Low Total ecosystem energy High Low Radiation intensity when clear Low High UV intensity Low High Partial pressure of CO2 High Low 1000 1500 2000 Altitude (m) below forest below grassland Nothofagus forests, South Island, New Zealand, in midsummer 0 500 8 10 12 14 16 18 Temperature at 20 cm soil depth (°C) below forest Körner et al. (1986), triangle Greer (1978), in: Ch Körner (2003) Alpine plant life. Springer, Berlin. Soil under alpine vegetation is warmer than under treeline trees rature at 10 cm soil depth (°C) Vaccinium heath (420 m) Treeline (420 m) N-Sweden Abisko 68° N Swiss Alps Valais, Furka 46° N Treeline (2240 m) Alpine grassland (2500 m) -5 0 5 10 15 Daily mean root zone tempe J J F M M A A J J S O N D Himalaya Langtang 28° N Alpine grassland (4010 m) Treeline (3980 m) Alpine grassland (4000 m) Mexico Iztlaccihuatl 19° N Treeline (4000 m) 5 -5 0 5 10 15 J J F M M A A J J S O N D Treeline: Energy flux in forests and low vegetation 15 °C 8 -10 °C warm cool 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 n=2 1 12 2 2 6 3 2 4 6 8 n temperature, T (°C) G (d) 6.7 ± 0.8 °C G T A global mean of 6.7 °C at treeline 0 2 4 Seasonal mean 70 60 50 40 30 20 10 0 10 20 30 40 Latitude (°C) 0 100 200 300 Growing period N S G Ch Körner, J Paulsen (2004) J Biogeogr 31:713 Ch Körner, J Paulsen (2004) J Biogeogr 31:713-732
Treeline formation Environmental explanation of treeline (1)The stress hypothesis (2)The maturation time hypothesis (3)The disturbance hypothesis (4)The reproduction/germination Loca2ogmaomgera hypothesis Biological explanation of treeline 1.The stress hypothesis (5)The carbon balance hypothesis (6)The growth limitation hypothesis impair tree growth Radiation 2.The maturation time hypothesis stress Maturation of leaves, shoots,fruits,and bud 4
4 Treeline Treeline formation formation Global drivers 'general principle' Regional drivers general principle 'modulation modulation' General physioecological explanation Local environmental explanations (1) The stress hypothesis (2) The maturation time hypothesis (3) The disturbance hypothesis Environmental explanation of treeline ( ) y (4) The reproduction/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 (5) The carbon balance hypothesis (6) The growth limitation hypothesis Biological explanation of treeline 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 1. The stress hypothesis • Repeated damage by freezing, frost desiccation or phototoxic effects impair tree growth Tranquillini, W. 1979. Physiological Ecology of the Alpine Timberline Radiation stress Evergreen Pinus cembra has a hard time in late winter, when exposed to bright sun with zero photosynthetic activity due to cold temperatures. Other species as for instance Larix decidua (in the background) avoid such problems by shedding their leaves in autumn. With this strategy, they can grow in the coldest place on earth, in sub-polar western Siberia. Maturation of leaves, shoots, fruits, and buds 2. The maturation time hypothesis e.g. seed maturation of Pinus sylvestris needs at least 600 – 890 GDD (growing degree-days >5°C) Odum 1979 In late summer, an early frost can prevent the completion of reproduction
3.The disturbance hypothesis Wind effects on plant growth c dam Wind effects on local treeline formation Avalanches on and the char Mortality mal disturbances 5
5 Mechanic damage by wind, ice blasting, snow break and avalanches, fire…… 3. The disturbance hypothesis Animal disturbances such as herbivory: Fungal pathogens; Man-made impacts such as grazing Tranquillini, W. 1979. Physiological Ecology of the Alpine Timberline Helianthus annuus Wind effects on plant growth Martin & Clements, 1935, Plant Physiol. 10, 613-636 0 5 10 15 • The altitudinal position and the character of the treeline may be winddetermined, i.e. the altitudinal limit of tree growth is lowered by strong and regular winds. Wind effects on local treeline formation Rocky Mountains National Park Avalanches Animal disturbances Mortality Fate of seedlings of Picea abies (Norway spruce) in a subalpine spruce forest after the first winter. Most individuals were killed by the Herpotrichia nigra (snow mould) and by mice. A dense web of Herpotrichia nigra hyphae around a low branch of small spruce. The parasitic fungus grows preferably in air pockets around branches in the snow