Climate change and plant-herbivore
interactions in boreal and arctic
ecosystems
Pekka Niemelä
University of Turku
BACCI - report
Changes in snow cover
Kellomäki et al.
Effect of climatic change on growth of Scots pine (Kellomäki et al.)
Deciduous trees benefit climatic change
Cental European climate?
Climate change can affect plant-herbivore
interaction by several mechanisms:
Quality of host plants changes
Growth and life cycle of herbivores changes
Habitat conditions (abiotic) changes
Trophic interactions changes
Predators, parasites, pathogens, etc…
Mekrijärvi chamber experiment
16 chambers:
-Elevated CO2
-Elevated Temperature
-Elevated CO2 and Temp.
-Control
Test plants:
-Pine
-Birch
-Willows
The effect of climatic change on resistance of birch Kuokkanen et al.
• Fertilization
decreses the level
of defence
•CO2 + T
decreases the
defence level
•Interaction
between soil and
climate!
Carbon/nutrient-balance
•The balance beween
nutrients and carbon
regulates the level of
defence against
herbivores
Compensatory growth in relation to climatic change
Birches grown in:
1. elevated CO2 and
2. temperature under
3. optimal N fertilisation,
4. defoliation levels from
25-75% of leaf biomass
Cont, 25, 50, 75%
defoliation
Forest defoliations in North-West Russia
Kozlov & Shelikovkin,
unpub.
L
Intensity of defoliation has increased
Number of outbreaks has increased
The effect of winter temperatures
Low winter temperatures may
kill the overwintering eggs
Pine sawfly (Neodiprion
sertifer)
outbreaks in pine forests
Autumnal moth (Epirrita
autumnata)
Huge outbreaks in
mountain birch forests
Pines defoliated by pine sawfly (Neodiprion sertifer)
Life cycle of N. sertifer: overwinters as an egg
Distribution of Neodpirion sertifer
Distribution in central
and southern Finland
Areal distribution of outbreaks of N. sertifer
Cold hardiness of the eggs of N. sertifer
Veteli et al. 2005
Effect of climate change on winter
temperatures
The effect of climate change on the frequency of
outbreaks
Egg parazitism and coldhardiness of eggs Veteli et al.
Temperature
”window” to escape
parazatism
Mountain birch forest killed by Epirrita autumnata
Some birches have
survived
Larva of E. autumnata
Eggs are owervintering on twigs
Tenow 1972
Outbreaks of Autumnal moth
Norway, Tana, 2003; Lauri Kapari
Topographical distribution of damages
Neuvonen and Virtanen 1998
Tenow 1972
“Lake of cold air”
”Lake of cold air”
in rivervalleys
High egg
mortality in
rivervalleys
Neuvonen and Virtanen 1998
Neuvonen and Virtanen 1998
Climatic change and
outbreaks in river
valleys
Conclusion
During mild winters outbreaks increase also
in rivervalleys
Climate change will increase the outbreak
frequencies of Autumnal moth
Norway, Tana, 2003; Lauri Kapari
Topography of outbreaks
Why dwarf birches have been defoliated?
Winter moth (Operopthera brumata)
Tenow 1972
Defoliation history
(Jepsen et al. 2009)
2002-03 Epirrita
2004-06 Operophtera
2007-09 Operophtera
Vegetation map: Johansen (2009)
Defoliation map: Jepsen et al. (2009)
New geometrid moth entering into mountain birch forests
Growth of reindeer population in Finland
Effect of reindeer
grazing on
vegetation
Den Herder et al, 2000
Moth-reindeer-birch interactions
Climate change has increased geometrid
moth outbreaks
How recovery of mountain birch forests is
affected by reindeer grazing?
WP 4: Moth-Reindeer-Birch Dynamics in Northernmost
Fennoscandia
Leader: Pekka Niemelä (Turku, Finland)
Co-leader: Rolf Anker Ims (Tromsö, Norway)
Researchers and collaborators:
Jane Jepsen (Tromsö, Norway)
Otso Suominen (Kevo, Finland)
Tero Klemola (Turku, Finland)
Piippa Wäli (University of Oulu, Finland)
Annu Ruotsalainen (University of Oulu, Finland)
Anna-Maija Markkola (University of Oulu, Finland)
+ doctoral students, postdocs
Rich – Low density
Poor – Low density
Poor – High density
Pulmankijärvi/Polmak lake
Reindeer density contrast
Vegetation map: Johansen (2009)
Distribution of defoliation in the area
Vegetation map: Johansen (2009)
Defoliation map: Jepsen et al. (2009)
How to study moth-reindeer –birch interaction?
Paired exclosure plots with different accessibility to herbivores
Large herbivore exclosure
Small + large herbivore exclosure (with mesh roof)
Study plot without exclosure
S S+L no
no
no
no
no
S
S
S
S
S+L
S+L
S+L
S+L
2 m
30 m?
30 m?