Uneven-aged management options
to promote forest resilience:
effects of group selection and harvesting intensity
Presented by Guillaume LAGARRIGUES
Co-authors : Valentine Lafond , Thomas Cordonnier , Benoît Courbaud
National Research Institute of Science and Technology for Environment
and Agriculture (IRSTEA) – Center of Grenoble
With the collaboration of Andreas Zingg
Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)
The 9th IUFRO International Conference on Uneven-aged Silviculture
17/06/2014
Adaptation of forest management to climate change
Uncertainties about
climate change
consequences
(Beniston et al. 2007)
Precautionary approach:
promote forest resilience by
enhancing species diversity
and uneven-aged structure
(Puettman 2011 ; Seidl et al. 2011)
Managements options to promote forest resilience
Uneven-aged silviculture framework
(Cordonnier et al. 2008)
Create forest gaps by
group selection
(Streit 2009)
Enhance natural
regeneration
Regenerate shadeintolerant species
Intensify harvesting
(Diaci and
Firm 2011)
Simulation experiments
Initial state
Forest dynamics
simulation model
Silviculture algorithm
Design of simulation experiments
(Lafond et al. 2014)
Stand area : 4ha ; Simulation period: 150 years, with cuts every 10 years
•
1st
experiment : spatialization of
cuts
• Standard harvesting intensity
• 7 modalities of spatialization
o Individual selection
o Small groups (20 – 1 000m²)
o One large gap at a time
• 2nd : harvesting intensification
with individual selection
• 4 modalities of harvesting intensity
• 3rd : harvesting intensification
with group selection (500 m²)
• 4 modalities of harvesting intensity
ILLUSTRATION
Initial state
Abundance (trees / ha)
1905
Diameter class
Permanent plot located in the canton of Bern in Swiss, monitored by the WSL of Zürich
Samsara : an individual-based forest model
Model calibration for this study
Observed data
in 2009
Abundance (trees / ha)
1905 – Initial state
Calibration of
model
parameters
Samsara
Predictions
Diameter class
Inverse modeling to calibrate the stand dynamics model so that model predictions fit to
historical data (Lagarrigues et al., submitted)
Modeling natural regeneration
Number of
recruits
Norway
spruce
Silver fir
Limitation by low
light conditions
Limitation by low
density of seed
bearers and
competition with
pioneer species
% of full light
Management modeling by a silviculture algorithm
(Lafond et al. 2013)
G (m²/ha)
𝑃𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 ℎ𝑎𝑟𝑣𝑒𝑠𝑡 =
Gh ×𝐻𝑎𝑟𝑣𝑒𝑠𝑡𝑖𝑛𝑔 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛
G max
G standard
N (t/ha)
Gh
G min
Ø (cm)
Øh = 27,5 cm
Results of the 1st experiment (spatial aggregation of cut trees)
Size diversity
(Gini index)
Uneven-aged
Species mix
(% of spruce basal area)
Species balance
Even-aged
Aggregation area (m²)
Aggregation area (m²)
2nd experiment (harvesting intensity with individual selection)
Size diversity
(Gini index)
Uneven-aged
Species mix
(% of spruce basal area)
Species balance
Even-aged
Proportion of potential
harvesting (%)
Proportion of potential
harvesting (%)
3rd experiment (harvesting intensity with group selection)
Size diversity
(Gini index)
Uneven-aged
Species mix
(% of spruce basal area)
Species balance
Even-aged
Proportion of potential
harvesting (%)
Proportion of potential
harvesting (%)
Management durability
2nd experiment
3rd experiment
Basal area (m²/ha)
1st experiment
Aggregation area (m²)
Proportion of potential
harvesting (%)
Proportion of potential
harvesting (%)
Main conclusions and limitations
Creating gaps and increasing harvesting intensity are both key management
options to drive species mix and size diversity in spruce-fir stands
Small-sized gaps (around 500m²) are sufficient to enhance natural regeneration,
but large openings (> 1 000m²) may be necessary to increase proportion of
shade-intolerant species such as spruce
Harvesting intensity: trade-off between durability and spruce maintenance
Group selection amplify harvesting intensity effects : forest management
coupling both options should be applied with care
Simulations are very sensitive to regeneration parameters
(see Lafond et al. 2014; Courbaud et al., submitted)
• Regeneration response to light must be calibrated accurately
• Conclusions only valid in forest conditions close to those used for model calibration
Research perspectives with this silviculture algorithm
•
Distinguishing thinning from harvesting
operations
•
Driving species mix directly by choosing
the trees to harvest according to their
species
•
Driving forest stand structure and
composition for biodiversity conservation
•
•
•
Preserving rare species
Sparing some very large trees
Leaving more dead wood in stands
Thinning
potential
Harvesting
potential
Thinning
diameter
Harvesting
diameter
=> See poster session : Studying the response of timber production
and biodiversity conservation to uneven-aged silviculture in
mountain forests (Lafond et al.)
Funding and acknowledgments
•
Guillaume Lagarrigues PhD
•
•
•
•
Projects
•
•
•
The French Environment and Energy Management Agency (ADEME)
The French National Forest Office (ONF)
IRSTEA (Grenoble, France)
French research program “Biodiversity, Forest Management and Public
Policy” (BGF)
European Research project “Advanced multifunctional forest management
in European mountain ranges” (ARANGE)
Data for model calibration
•
Swiss Federal Institute for Forest, Snow and Landscape Research (Zürich)
Thank you for your attention !
References
Beniston, M., Stephenson, D. B., Christensen, O. B., Ferro, C. A. T., Frei, C., Goyette, S., Halsnaes, K., Holt, T., Jylha, K.,
Koffi, B., Palutikof, J., Schoell, R., Semmler, T. & Woth, K. (2007). Future extreme events in European climate: an
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Cordonnier, T., Courbaud, B., Berger, F. & Franc, A. (2008). Permanence of resilience and protection efficiency in mountain
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Courbaud, B., de Coligny, F. & Cordonnier, T. (2003). Simulating radiation distribution in a heterogeneous Norway spruce forest
on a slope. Agricultural and Forest Meteorology 116(1-2): 1-18.
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Uneven-aged silviculture give managers many options to harvest wood
while preserving forest resilience. Among them, we chose group
selection and is favorably considered as forest gaps can enhance
natural regeneration, especially for shade-intolerant species. Intensify
harvesting is another interesting option that can allow reduce the
amount of very large trees, reducing thus the risk of tree senescence
and diseases while enhancing also natural regeneration by providing
more light to the ground. However, such fine details about unevenaged management have been poorly studied until now, and many
questions remains about the efficiency of these options and the scales
at which they should preferably applied.