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
1. Definition of the alpine treeline
2. Driving forces of treeline formation
3. Upword shifts of the alpine treelines,
corresponding to global warming, in
the Himalayas and worldwide
4. Physioecological machanisms of the
alpine treeline shifts
5. Conclusions
Treelines across the globe
---a virtual site visitation
9
Davos, Swiss Alps
2 3
10
4 5
1
12
11
14 13
6
7
8
The Himalayas
16
15
17
18
19
20
Ch Koerner, J Paulsen 2004
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
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
6
2
n=2
1 12
2
6.7 ± 0.8 °C
T
2
6
3
4
G
300
200
2
100
0
70
N
60
50
40
30
20
10
0
Latitude (°C)
10
20
30
40
S
0
Growing period G (d)
Seasonal mean temperature, T (°C)
A global mean of 6.7 °C soil temperature (-10 cm
depth) for growing season at treeline
Ch Körner, J Paulsen (2004) J Biogeogr 31:713-732
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
Location
Authors, year
Species
Upword
shift (m)
Period
(year)
Rate
(m/yr)
South Island,
New Zealand
Wardle & Coleman,
1992
Nothofagus menziesii, N.
solandri
7-9
1930-90
0.12-0.15
Italian Alps
Leonelli et al. 2010
115
1901-2000
1.15
Glacier N.P.
Montana
Bekker, 2005
Picea engelmannii, Pinus
contorta, Abies lasciocarpa
7-16
1800-1980
0.28-0.62
Sunwapta
Pass, Alberta
Luckman &
Kavanagh, 2000
P. engelmannii, A.
lasciocarpa
145
1700-1994
0.5
Uinta Mts. UT
Munroe, 2003
P. engelmannii, A.
lasciocarpa
61-183
1870-2001
0.5-1.4
SW Yukon
Danby & Hik, 2007
Picea glauca
65-85
1920-2005
0.8-1.0
Scands Mts,
Sweden
Kullman, 2001
Betula pubescens, Pinus
sylvestris, Picea abies
100-165
1915-2000
1.2-1.9
Kootenay NP,
B.C.
Roush, 2009
Larix lyallii, P. engelmannii,
A. lasciocarpa
149
1909-1976
2.2-5.7
W. Himalayas
of India
Dubey et al. 2003
14-19
Over
10 yrs
1.4-1-9
Baima Snow
Mt, Yunnan
Baker & Moseley,
2007
67
Since
1923
Nanda Devi in
C. Himalaya
Panigrahy et al., 2010
300
Since
1960
Himalayas,
Nepal
Vijayaprakash &
Ansari, 2009
Abies spectabilis
N-aspect
South-asp.
1.7 (N-s)
2.3 (S-s)
Each species is likely to respond to
climate change in its own way:
Species
No.
Elevation (1970) Elevation (1992) Elevational shift (m)
Vaccinium uliginosum
11
2216
2216
0
Vaccinium vitis-idaea
30
1898
1885
-13
Vaccinium myrtillus
31
1972
2002
30
Rhododendron ferrugineum
30
2098
2098
0
Pinus cembra
31
2064
2005
-59
Hieracium pilosella
13
1851
1930
79
Scleropodium purum
26
1425
1630
205
Dupouey et al. 1997
Treeline formation
Global drivers
'general principle'
General physioecological
explanation
Regional drivers
'modulation'
Local environmental
explanations
Environmental explanation of treeline
(1) The stress hypothesis
(2) The maturation time hypothesis
(3) The disturbance hypothesis
(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
Biological explanation of treeline
(5)The growth limitation hypothesis
(6)The carbon 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
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
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
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
3. The disturbance hypothesis
Mechanic damage by wind, ice blasting, snow
break and avalanches, fire……
Animal disturbances such as insect
Fungal pathogens
Man-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
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
5. Growth limitation
6. Carbon limitation
Growth
Photosynthesis
Photosynthesis
Growth
“Sink“ driven
“Source“ 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
Source limitation hypothesis:
Tree growth is considered source limited
when carbon assimilation through photosynthesis is insufficient to meet growth
requirements.
Sink limitation hypothesis:
Trees are considered carbon sink limited
when there is an abundant supply of the
resources necessary to support growth, but
growth itself is directly limited by environmental conditions.
Cell doubling time
Mitotic time
100
200
50
100
0
0
Ch Körner (2003)
Alpine Plant Life. Springer, Berlin
10
20
30
Temperature (°C)
40
20
10
0
Mitotic time (h)
30
Net-photosynthesis (%)
Cell doubling time (h)
300
Non-structural carbohydrates + lipids
in stem sapwood (% d.m.)
4
Mexico (19° N)
Pinus hartwegii
Pinus cembra
*
*
Alps (46° N)
Sweden (68° N)
Pinus sylvestris
Lipids
End of winter
2
NSC
0
4
**
Mid season
2
0
***
4
Late season
2
0
Low High
Low
High
Altitude
Low High
G Hoch & C Körner (2003)
Oecologia 135:10-21
200
160
Branchwood
a
ab
b
50
40
a
a
a
Stemwood
50
40
120
30
30
80
20
20
40
10
10
0
0
0
4360 4550 4810
4360 4550 4810
a
a
a
Starch
Leaves
Sugars
NSC concentrations (mg cm3)
Polylepis tarapacana, Volcano Sajama, Bolivia
4360 4550 4810
Elevation (m a.s.l.)
NSC=Non-structural carbohydrates = solube sugars + starch
G Hoch & Ch Körner (2005) Funct Ecol 19, 941-951
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
1-yr-old
needles
25
2-yr-old
needles
*
3-yr-old
needles
Starch
**
*
*
20
Sugars
Fine roots
15
Carbon shortage? - Yes! Stem wood
a
b
a
b
a
b
a
b
a
b
3400m
3800m
3400m
3800m
3400m
3800m
3400m
3800m
3400m
3800m
3400m
April
July
April
July
April
July
April
3400m
3800m
3400m
3800m
0
July
a
b
April
3400m
b
3800m
a
B
3400m
A *
5
*
3800m
10
3800m
Starch / Sugars / NSC concentration (% d.m.)
30
July
Elevations of trees and sampling time
Picea balfouriana var. hirtella
Li MH et al. 2008. Tree Physiology 28, 1287-1296
Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387
An overall trend in NSC – 3 treelines data pooled
Soluble sugars
April
July
Starch
April
July
NSC
April
July
Three treeline cases combined (Lower E trees = lower elevation trees)
Treeline trees
11.09
10.51
3.61
4.19
14.70
14.70
Lower E trees
10.66
10.37
4.77
4.55
15.43
14.91
F1,89
3.53
0.24
31.00
1.35
6.80
0.31
p
0.07
A winter C-shortage
0.63
<0.001
0.25
0.011
0.58
Li MH et al. 2008. Tree Physiology 28, 1287-1296
Li MH et al. 2008. Plant, Cell & Environment 31, 1377-1387
???
A winter carbon shortage?
or
An effect of phenological phase-shift?
Hoch G. 2003
PhD thesis
Uni. Basel
Krummholz
Dead individuals
Seedlings
Adults
Tree species line
Timberline
Camarero & Gutierrez (2002) Plant ecology 162: 247
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
• Plants may also respond to climate change 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
Modeled Climate-Induced Glacier and Vegetation Change in Glacier National
Park, 1850-2100
http://www.nrmsc.usgs.gov/images/glacier_animation_slow.gif
30
Podocarpus oleifolius
2550 m a.s.l.
3200 m a.s.l.
Espeletia neriifolia
2400 m a.s.l.
Cavieres et al. 2000.
Acta Oecologia 21, 203-211
3200 m a.s.l.
Abies balsamea
Picea rubens
Shade needles
P<0.05
P<0.05
P<0.05
Sun needles
P<0.05
Richardson AD. 2004
Plant & Soil 260,
291-299