Surely you have noticed that the number of spruce stands in the Czech Republic has been declining in recent years, as the spruce bark beetle has multiplied. You can already observe the clearings after bark beetle mining in the Kostelec region (one of our research sites). One of the reasons why spruces are so much infested by the bark beetle is the lower precipitation totals in recent years and the associated limited availability of water in the whole soil profile. Spruces that have a shallow root system are affected and suffer from long-term stress. Stress reduces their ability to defend against pests, and this leads to an overpopulation of the population of this aggressive bark beetle. Bark beetles are a natural part of forest ecosystems and, in their normal state, attack only weakened trees. Many of the healthy ones resist and the bark beetle population is naturally regulated in this way. However, if the forest is weakened, for example by drought, it will also attack completely healthy trees. When synchronizing the occurrence of stressed trees in a large area or after large winds, conditions are created for the formation of bark beetle calamities.
In our research, we focused on the effect of water shortage on the condition of adult spruces. We find out how the gradual drying will change the individual physiological parameters of the trees and under what conditions the tree can no longer defend itself against the bark beetles. In such a controlled experiment, we will learn to recognize the physiological state of spruces by various imaging methods placed on a drone or on the basis of aromatic substances excreted from trees. See the video on YouTube for more information.