Effects of management and natural

disturbances on vegetation carbon

pools in mountain forests

Urs Gimmi, Annett Wolf, Matthias Bürgi, Marc

Scherstjanoi, Harald Bugmann

Background

– Effects are difficult to disentangle

– Regional case studies based on detatiled historical

evidence are valuable for in-depth analysis of

disturbance effects on vegetation carbon pools

Forests store 10-20 times more C in their biomass

per area unit then all other land cover types (Olson

et al. 1983)

Natural disturbances and forest management affect

carbon pools stored in forest vegetation and alter

biogeochemical cycles (Houghton et al. 2000)

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

General research aim

Reconstruct dynamics in forest

vegetation carbon pools and quantify

effect of natural and anthropogenic

disturbance over the past 100 years

for an alpine valley (Alptal)

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Specific research aims

• Reconstruct centennial time series for

– Forest dynamics (standing volume, species composition,

growth increment etc.)

– Anthropogenic and natural disturbances

→ vegetation carbon pools

• Quantify relative contribution of managment and natural

disturbances on dynamics in vegetation carbon pools

• Assess C storage capacity of forests in the region and

potential for future C-accumulation

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Forest history before 1900

• Alptal was an important timber source for the city of

Zurich since the 16th century (Bitterli 2004)

• Large clearcuts until the late 19th century

• Large-scale reforestation activities started in the

1880s (Bitterli and Lienert 2007)

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Forest history before 1900

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Plans contain three different perspectives: (A) Past: Report on past forest use and

management

(B) Present: Stand description, inventory

(C) Future: Planning

Alptal • 9 owners/25 MPs between 1924-1983 &1999

• 70% of the forested area

• Annual records of timber harvesting and wood removal due to natural disturbances

Forest Management Plans

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Results: Changes in standing volume

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Av. volume per

tree increased

from 0.7 to 0.9 m3

Larger diameter

promoted by forest

management

Only slight

increase in forest

area

Gimmi et al. 2009

Results: Changes in species

composition 1925 1950 1975 1999

Spruce (%) 76 80 78 75

Fir (%) 17 14 16 18

Beech (%) 7 6 6 7

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

0

5

10

15

20

25

30

1906-

1915

1916-

1925

1926-

1935

1936-

1945

1946-

1955

1956-

1965

1966-

1975

1976-

1985

1986-

1995

1996-

2005

10

3 p

lan

ts

deciduous trees

other conifers

Fir

Spruce

Results: Disturbance history

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

0

5

10

15

20

25

30

35

40

451

90

5

19

15

19

25

19

35

19

45

19

55

19

65

19

75

19

85

19

95

20

05

10

3 m

3

wind throw bark beetle other disturbances timber harvest

→Constant timber harvesting

→Two major storm events (1990 & 1999) with subsequent

bark beetle infestations

Only data for total removal

available

Results: trajectories of forest

change

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Calculating carbon pools

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Conversion

factor (ρ)

Expansion

factor (e)

C-content

spruce & fir 0.4 1.48 0.5

beech 0.55 1.49 0.5

Procedure for converting growing stock into vegetation

carbon stock

→ IPCC standard methodology (Penman et al. 2003)

→ applying species and region specific values (Thürig and Schmid 2008)

Results:

changes in vegetation carbon pools

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

0

25

50

75

100

125

150

175

200

225

Potential

Vegetation

1925 1950 1975 1999

tC *

ha

-1

conifers deciduous trees

Gimmi et al. 2009

1925 -1950

Forest

expansion

Tree

growth

Timber

harvesting

Natural

disturbances

1950 -1975 1975 -1999 1999 -2006

Veg

C-pool

1925

Potential future C-accumulation

• Forest expansion?

→ limited / conflicts

• Maximazing C-stocks?

→ forest become more susceptible to

natural disturbances

potential for further C-accumulation in

forest vegetation is strongly limited

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

Conclusions

• High rates of C-accumulation in the first 50 years result from:

→ management was able to compensate for losses caused by previous unsustainable logging within a few decades.

• Regional forests have limited potential for future C-accumulation

• Regional-scale historical ecological studies provide reference conditions show ecosystems's historical range of variability (relevant for planning)

Gimmi et al. @ Global Change and the World's Mountains, Perth 2010