The overall aim is to understand the mechanisms of conifer tree-bark beetle interactions on the tree level. One hypothesis is that drought stress predisposes the tree to bark beetle attack.
We aim to understand the connections of genetics, tree health (physiology), susceptibility, and resistance to bark beetle, including the chemical messengers involved such as attractants and anti-attractants. Rapid detection of tress under stress or beetle attack is a more direct applied goal.
Detection of Trees under Stress
This research is based on the observation that the stressed trees seems to be more likely to be attacked. Experimental plots are established in spruce forest with low, endemic bark beetle population where trees will be exposed to sun or drought stress. Inoculation bioassay with bark beetles will be performed there. In addition, the observational plots established in spruce forest with high, epidemic bark beetle population will observe natural bark beetle populations attacking naturally stressed but physiologically monitored spruces (Pictures above, photo S. Netherer). The trees condition and vulnerability for bark beetle attack will be measured by several approaches.
Prediction of tree stress by physiology
First, we use the physiological approaches to quantify the physiological stress of trees compared to the susceptibility to bark beetle attack. Among others, the sap flow measurement is the most important physiological instrument as it reveals the cooling abilities of the tree. Normally, the water consumption is 15 - 65 l/day depending on stem diameter. With prolonged period of drought, the tallest tree has the same transpiration as smaller trees with suppressed crown (ca 5 l/day). The hypothesis we are working on is the higher level of drought stress in trees with bigger diameter compared to smaller ones. If the smaller trees could restrict the transpiration 3X under drought, the large trees would have to lower the transpiration > 10X. The tallest trees in the forest of the same age may then be the first targets for bark beetle.
Figure 1. Sap flow meter EMS81 with isolation: The instrument for sap flow measurement is based on thermodynamic method and the insulation layer should cover the instrument to prevent the heat from outside. Photo: I. Tomaskova
Figure 2. EMS81 without isolation: This instrument take a 10minutes measurements of stem diameter and water movement within the xylem. The dendrometer is very sensitive to stem volume changes so the shrinkage, swelling and real growth of the stem is being recorded. Sensors below the dendrometer records the water amount per 1 cm of the stem perimeter. Photo: I. Tomaskova
Figure 3. Meteo station consist of anemometer, global radiance sensor, sensor for air temperature and relative humidity, precipitation gauge and sensors for soil humidity in two depths. Photo: S. Netherer
Figure 4. Receiver and sender is the equipment enabling wireless data transfer to internet portal. Data are stored for 5 years here. Pair of spare batteries are inside of the metal box in case of insufficient energy from solar panels. Photo: S. Netherer
FIgure 5. Solar energy runs all physiological equipment. The energy is stored in batteries. Photo: S. Netherer
The second approach will be dendroecological techniques (analysis of annual growth rings) which will show the past annual tree growth and stress inputs based on the tree rings in combination with isotope signal in the tree rings.
Chemical constituents and messengers (Chemical Ecology)
Figure GCxGC-MSTOF A): Principles of operation.
Figure GCxGC-MSTOF B): Post-run analysis. More info on lab in operation see https://extemit.fld.czu.cz/en/r-12327-vizual/modern-chemical-ecology-laboratories-are-fully-in-operation.html
Third, the volatile and less volatile compounds as the possible bark beetle attractant and anti-attractants as well as defense compounds and primary metabolites for will be collected and identified by chromatographic methods (Figure GCxGC-MSTOF).
The experimental trees will be genetically characterized to understand the connections of tree physiology and metabolism to tree susceptibility and resistance to bark beetle attack.
Early warning by remote sensing of change of spruce needle reflectance connected with drought stress measured by aerial hyperspectral scanner
From (Näsi et al., 2015)
Remote sensing methods will be used for detection of the stressed trees in the experimental and observation stands. Our working hypothesis is that the changes in needle physiology and lower cooling abilities of stressed trees prior and after bark beetle attack affects needle reflectance. We will mount the spectral scanners to the drones which will help to make an overview of the countryside. The knowledge about connection of tree physiology and tree reflectance can be used for detection and mapping of trees susceptible to bark beetles, tree resistance to bark beetle attack, and early attack detection. An additional hypothesis is that the expansion of bark beetle infestations depends on spatial distribution of susceptible and resistant trees and on mechanism of spreading – including stand light conditions.
Real-time detection by thermal emission under different crown and stand geometry
Thermal scanning will be used for detection of the stressed trees in the experimental and observation stands. Drought stressed trees with higher temperature of bark or needle can hypothetically serve as first targets of beetle attack. An important factor connected with temperature changes on bark and needles is sun insulation in connection to crown geometry. Therefore, the real-time detection of stressed trees with poor cooling properties by medium-range thermal imaging or connected with tree crown geometry will be scanned. The surface temperature will be mapped either by the aerial - terrestrial laser scanner or image-based structure, where the architecture can be evaluated.
Chemical Indicators, Anti-attractants, and Semiochemical Signals
The second point of view at the conifer tree-bark beetle interactions on the tree level focusing mainly on chemical compounds with the communication function for bark beetles.
Field activity of new physiology active semiochemicals and blend function
We will test the field activity of the new lab-active potential anti-attractants, compounds which reduce attraction or host-acceptance in I. typographus. Anti-attractants are emitted by fungi or by the non-host angiosperm tree. Anti-attractants may come also from the resistance compounds of the attacked host tree or from switching pheromone of the attacking beetles. In our experiments will be paid special attention to the new combinations of anti-attractants of different activity mode, which can change the range-of-action of non-host volatiles-dispensers (used later in Level L). We will test the activity of the new anti-attractants by trapping I. typographus in and around its pheromone traps and we will study the protection of the single tree by anti-attractants.
Establishment of rapid attacked tree detection/diagnosis by sniffer dogs
Snifferdog BeBe indicating an early attack on a mature tree. Blue-red arrow) GPS dog collar with antenna.
We aim to establish the method of rapid attacked tree detection by snifferdog-handler pairs for prompt removal of attacked trees. The structure of this research item is different from all the others in that it has a large element of demonstration. We expect a full success and acceptance of the method by Czech dog trainers and foresters, probably followed by founding of fully commercial small service companies.
Jakuš R, Zajíčkova L, Cudlín P, Blaženec M, Turčani M, Ježík M, Lieutier F, Schlyter F (2011) Landscape-scale Ips typographus attack dynamics: from monitoring plots to GIS-based disturbance models. iForest-Biogeosciences and Forestry 4: 256. doi:
Näsi R, Honkavaara E, Lyytikäinen-Saarenmaa P, Blomqvist M, Litkey P, Hakala T, Viljanen N, Kantola T, Tanhuanpää T, Holopainen M (2015) Using UAV-based photogrammetry and hyperspectral imaging for mapping bark beetle damage at tree-level. Remote Sensing 7: 15467-15493. doi: