Effects of management and natural disturbances on vegetation carbon pools in mountain forests. Presented by Urs Gimmi at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

1. Effects of management and natural
disturbances on vegetation carbon
pools in mountain forests
Urs Gimmi, Annett Wolf, Matthias Bürgi, Marc
Scherstjanoi, Harald Bugmann

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

3. 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

4. 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

5. 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

6. Forest history before 1900
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

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

8. Results: Changes in standing volume
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
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

9. Results: Changes in species
composition
1925 1950 1975 1999
Spruce (%) 76 80 78 75
Fir (%) 17 14 16 18
Beech (%) 7 6 6 7
30
25
20 deciduous trees
103 plants
other conifers
15
Fir
10 Spruce
5
0
1906- 1916- 1926- 1936- 1946- 1956- 1966- 1976- 1986- 1996-
1915 1925 1935 1945 1955 1965 1975 1985 1995 2005
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

10. Results: Disturbance history
45
40
35
Only data for total removal
30
available
3
10 m
25
3
20
15
10
5
0
1905
1915
1925
1935
1945
1955
1965
1975
1985
1995
2005
wind throw bark beetle other disturbances timber harvest
→Constant timber harvesting
→Two major storm events (1990 & 1999) with subsequent
bark beetle infestations
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

11. Results: trajectories of forest
change
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

12. Calculating carbon pools
Conversion Expansion C-content
factor (ρ) factor (e)
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)
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

13. Results:
changes in vegetation carbon pools
225
200
175
150
tC * ha-1
125
100
75
50
25
0
Potential 1925 1950 1975 1999
Vegetation
conifers deciduous trees
Gimmi et al. 2009
Gimmi et al. @ Global Change and the World's Mountains, Perth 2010

14. 1925 -1950 1950 -1975 1975 -1999 1999 -2006
Timber Natural
harvesting disturbances
Veg
C-pool
1925
Forest Tree
expansion growth

15. 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

16. 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