The relationship between drought, tree vitality, mycorrhizal associations and spruce bark beetle attack

Spruce trees are very sensitive to drought and the climate change predictions are that drought events will become more common under future climate conditions.

The drought of 2018 and the devastation by spruce bark beetle (SBB) in its wake might give a bleak prediction for the future of spruce in Sweden. Hence, we need to understand the relationship between stand conditions and spruce susceptibility to SBB.

Recent studies showed that indeed drought makes spruce more vulnerable to SBB but it is not the driest stands that showed the highest damage.Hence, our project sets out to create a better understanding of the relationship between soil moisture conditions and spruce bark beetle susceptibility. One factor that so far has not been included in this research is tree symbiosis with mycorrhiza (EM).

Our project aims to investigate the relationship between soil moisture conditions, mycorrhizal colonisation and community composition and spruce resistance against spruce bark beetle attack.

We do this by using a soil moisture gradient to establish the effect on EM symbiosis and subsequently build roofs inselected to simulate drought and study consequences on EM symbiosis and tree susceptibility to SBB.

By the end of our study, we will be able to show the effects of drought on spruce-EM relationships and how this relationship affects SBB attack success. This information will be important for forest planning in the future.