Effects of new forest management on insect damage risk in a changing climate

Transcription

1 Effects of new forest management on insect damage risk in a changing climate Björkman, C., Bylund, H., Nilsson, U., Nordlander, G. and Schroeder, M. Swedish University of Agricultural Sciences Based on a book chapter manuscript for Climate Change and Insect Pests Editors - C. Björkman and P. Niemelä.

2 Insect forest pests Bark beetles the spruce bark beetle (Ips typographus) Regeneration pests-the pine weevil (Hylobius abietis) Defoliators several species

3 Defoliators Conifers Neodiprion sertifer the European pine sawfly Diprion pini - the large pine sawfly Bupalus piniarus the pine looper moth Lymantria monacha- the nun moth Dendrolimus pini the pine tree lappet moth Panolis flammea the pine beauty moth Deciduous trees Operophtera spp. the winter moth, geometrids Tortrix viridiana the European leaf roller Lymantria dispar the gypsy moth Zeiraphera griseana- the larch tortrix

4 Climate warming and forest insect pests?

5 Anticipated effects of climate change Insects are ectotherms. In northern areas they are in general expected to respond positively to increased temperature within a certain temperature range. Natural enemies Host plant

6 Climate warming and bark beetles Shorter development time Increased number of generations Storm fellings warmer winters Drought events

7 Climate warming and the pine weevil Shorter development time and generation time Larger fraction of weevils overwintering as adults in the soil feeding during autumn Longer growing seasons increased feeding damage in plantations

8 Climate warming and forest defoliators Shorter development time but not generation time Distribution and outbreak range will change Individualistic response of each species with potential changes in outbreak frequencies and population dynamics (cyclicity).

9 Forest management types reviewed Replacing even-aged spruce dominated forest in southern Fennoscandia. Continuous cover forestry: Mixed forests: Short rotation forestry: Exotic tree species: no clear-felling spruce birch and other species no thinning Conventional management: Even-aged stands, thinned 2-3 times before final clearfelling.

10 Continuous cover forestry The spruce bark beetle Storm damage? -/+ Mature trees always present but with larger gaps reduced risk? Natural enemies higher abundance? reduced risk Transition period - important to consider? The large pine weevil Less breeding material fewer stumps- reduced risk Natural regeneration reduced risk More or less shaded stumps reduced risk More scattered breeding substrate Defoliators Trees of different age and size- differences in food quality reduced risk Natural enemies- higher diversity and abundance? reduced risk Not much known!?

11 The spruce bark beetle Mixed forests Non-linear relationship spruce ratio and damage risk reduced risk - Storm damage? +/- More scattered suitable host trees - reduced risk The large pine weevil Less breeding material reduced risk Less attraction to clear-cut areas? Reduced risk -? Defoliators Tree species composition & specialist or generalist defoliators? Natural enemies- higher diversity and abundance? Reduced risk Different consequences for conifer and deciduous trees

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13 Short rotation forestry- no thinning The spruce bark beetle Fewer stands with suitable stem diameter reduced risk Storm damage +/-? The large pine weevil Increased densities more breeding substrate - increased risk + Planted regeneration increased risk + Defoliators Age class more important in some defoliator species +/-? Age class could affect tree recovery/mortality rate -/+?

14 The spruce bark beetle Exotic tree species Depends on tree species able to reproduce in North American spruce species +/- The large pine weevil Depends on tree species if suitable breeding substrate +/- Planted regeneration pine weevils are not picky: increased risk +? Defoliators Depends on tree species taxonomic affinity Invasive species! Chestnut leaf miner Cameraria ohridella

15 Pine weevil Defoliators Spruce bark beetle Continuous cover forestry Mixed forest Short rotation No thinning Exotic tree species

16 Conclusion Large knowledge gaps both effects of climate change and forest management on insect damage risks More research needed Field experiments & modelling more collaboration between entomology and silviculture researchers Combining data at different spatial scale landscape perspective Invasive species Can choice of forest management method mitigate risk of insect damage in a warming climate?

17 Thank you for your attention!