Global change at timberline in the Central European Alps

G. Wieser, W. Oberhuber, A. Gruber, R. Matyssek

Innsbruck / Munich

© G. Wieser Photo J. Wagner

The timberline ecotone

Krummholz-limit

Forest limit

Tree-limit

AfterTranquillini 1976, 1979© G. Wieser

What is Global Change?

Climate change

altered atmospheric chemistry

climate warming

Land use change

management, land abandonment

© G. Wieser

Climate change air temperature

1960 1970 1980 1990 2000 2010

Year

-30

-20

-10

0

10

20

30

Mo

nth

ly m

ea

n, m

ax

imu

ma

nd

min

imu

m T

air [

°C]

0

1

2

3

4

An

nu

al m

ea

nT

air [

°C]

Klimahaus Research Station, Mt. Patscherkofel 1950 m a.s.l. 1964 - 2007

Wieser unpublished© G. Wieser

Climate change air temperature

Mean 1963 -1994

Mean 1995-2004

Difference

Annual mean 2.1 3.1 +1.0

Winter -4.0 -3.4 +0.6

Spring 0.3 1.7 +1.4

Summer 8.9 10.5 +1.6

Fall 3.5 3.5 0

Vegetation period

168 196 +28

Wieser 2007© G. Wieser

Impacts of climate warming carbon balance – present situation

-15 -10 -5 0 5 10 15 20

Air temperature [C]

0

4

8

12

16

GP

P a

nd

ER

[g

C m

-2su

rfa

ce a

rea d

-1]

Day of year

-4

-2

0

2

4

6

8

10

Ca

rbo

n b

ala

nce

[g C

m-2

su

rfc

e a

rea d

-1]

305 3050 60 121 182 244 365

-30

-20

-10

0

10

20

30

40

T air

Presently warm growing season temperatures and their effect on ER are the key factors limiting NEP

Wieser and Stöhr 2005, Wieser 2007© G. Wieser

Impacts of climate warming carbon balance – future warmer climate

GPP + 15 %

ER + 10 %

NEP + 5 %

Temperature increase 1°C

0 30 61 91 122 152 183 213 243 274 304 335 365

Day of year

-200

-100

0

100

200

300

400

500

NE

P [

g C

m-2

]

0 30 61 91 122 152 183 213 243 274 304 335 365

Day of year

-200

-100

0

100

200

300

400

500

NE

P [

g C

m-2

]

Carbon sequestration may benefit from future climate warming

After Wieser and Stöhr 2005 and Wieser 2007© G. Wieser

Impacts of climate warming carbon gain of trees

0 2 4 6 8 10 12 14 16

Soil temperature [°C]

0

20

40

60

80

Da

ily C

O2 u

pta

ke [m

g g

dw

-1 h

-1]

0

5

10

15

20

T s

oil

[%]

Central European Alps

Pinus cembra

Soil tempertature also affects carbon gain

Havranek 1981© G. Wieser

Impacts of climate warming soil temperature and tree growth

Krummholz limitartificial soil cooling

Soil cooling caused a significant decline in stem diameter increment at the krummholz limit

Oberhuber, Gruber, Wieser unpublished© G. Wieser

100 150 200 250 300

Day of year 2007

0

5

10

15

20

So

il te

mp

era

ture

[°C

]

0

1000

2000

3000

4000

Ste

m d

iam

ete

rin

cre

me

nt

[m

]

0

100

200

300

De

gre

e d

ays

Global change treeline shifts – seedling re-establishment

Luzian and Pindur 2007

Seedling re-establishment results from invasion into potential habitats rather than an upward migration due to climate warming

© G. Wieser

Land use change carbon balance

Wieser and Stöhr 2005, Larcher 1977, Koch et al. 2008

Vegetation NEP [g C m-2 y-1]

Forest 360

Dwarf shrubs 210-250

Grassland and pastures 60-140

© G. Wieser

Land use change water balance

Matyssek et al. 2008, Wieser 1983, Guggenberger 1980, Kronfuss 1997

Alpine pasture

The vegetation type has a significant impact on the carbon and water balance

Vegetation ETI [mm y-1]

Forest 480

Dwarf shrubs 350

Grassland and pastures 280© G. Wieser

.

Conclusions

© G. Wieser

With respect to carbon gain, trees and stands will benefit from future climate warming

Invasion is a consequence of the currently decreasing grazing pressure on pastures, which has suppressed forest up-growth throughout centuries

This kind of habitat re-occupation suggests the tree line in the Central European Alps to behave in a conservative way.

.

Conclusions

© G. Wieser

Finally, one has to be aware that the alpine timberline in the Central European Alps is more susceptible to

human impact such as land use changes and management practices than to expected climate change.

In addition episodic extreme events by e.g. summer and/or frost drought, severe frost during the growing season or biotic stress (by pathogens/herbivores) rather than the gradual temperature increase will control tree population dynamics within the timberline ecotone of the Central European Alps in the future environment.

Thank you for your attention

© G. Wieser Photo K-H Häberle

Mining area opened 1272 closed 1967