Insect damage risk in continuous cover forests and forests managed in new ways.

Transcription

1 Insect damage risk in continuous cover forests and forests managed in new ways. Helena Bylund Dept. of Ecology, Unit of Forest Entomology Swedish University of Agricultural Sciences

2 Based on a book chapter manuscript for Climate Change and Insect Pests Editors - C. Björkman and P. Niemelä. Effects of new forest management on insect damage risk in a changing climate Björkman, C., Bylund, H., *Nilsson, U., Nordlander, G., and Schroeder, M. Dept. of Ecology, Unit of Forest Entomology, *Dept. of Southern Sweden Forest Research Centre Swedish University of Agricultural Sciences

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

4 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

5 Anticipated effects of weather & climate change Insects are ectotherms. In northern areas they are 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 Longer growing seasons increased feeding damage in plantations Larger fraction of weevils overwintering as adults in the soil feeding during autumn

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.

9 Forest management types 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 clear felling.

10 Continuous cover forestry The spruce bark beetle Storm damage?: large trees left, more resistant to storm thinnings may increase storm damage risk + Mature trees always present, suitable: + larger distance between trees: Natural enemies higher abundance?: Transition period important to consider: +

11 Continuous cover forestry The large pine weevil Fewer stumps less breeding substrate: Shaded stumps: Scattered stumps larger distance: Regeneration, natural regeneration:

12 Continuous cover forestry Defoliators Trees of different age and size differs in food quality?: Natural enemies- higher diversity and abundance?: Not much known!

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

14

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

16 Exotic tree species Lodge pole pine (Pinus contorta) hectares in Sweden Less common Douglas fir (Pseudotsuga menziesii) Sitka spruce (Pisea sitchensis) Hybrid larch (Larix eurolepis/marchinsii) Hybrid aspen (Populus tremula tremuloides) Clonal forestry

17 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: +? Defoliators Depends on tree species taxonomic affinity Invasive species! Chestnut leaf miner Cameraria ohridella

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

19 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?

20 Continuous cover forestry in Sweden A low proportion of multi-layered forests managed by selective thinning/cutting ( blädning ) Swedish Forest Agency from 1993 open for and encourage more diversified management methods Increased interest for alternative management methods to meet environmental demands Recently new experiments have been established: a) restoration of and maintaining multi-layered stands/mature stands b) transformation of even-aged stands to multilayered stands.

21 Continuous cover forestry in Sweden Drössler et al. 2014: Simulation of transformation of even-aged Norway spruce stands to multi-layered forests: possible to transform to mult-layered in 50 years. 30% reduced growth. Insects mainly studied from conservation point of view but new study on the pine shoot beetle and spruce bark beetle in restoration sites.

22 Thank you for your attention!