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?