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963 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